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Title 40: Protection of Environment

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PART 141—NATIONAL PRIMARY DRINKING WATER REGULATIONS 

Section Contents

Subpart A—General

§ 141.1 Applicability.

§ 141.2 Definitions.

§ 141.3 Coverage.

§ 141.4 Variances and exemptions.

§ 141.5 Siting requirements.

§ 141.6 Effective dates.

Subpart B—Maximum Contaminant Levels

§ 141.11 Maximum contaminant levels for inorganic chemicals.

§ 141.12 [Reserved]

§ 141.13 Maximum contaminant levels for turbidity.

Subpart C—Monitoring and Analytical Requirements

§ 141.21 Coliform sampling.

§ 141.22 Turbidity sampling and analytical requirements.

§ 141.23 Inorganic chemical sampling and analytical requirements.

§ 141.24 Organic chemicals, sampling and analytical requirements.

§ 141.25 Analytical methods for radioactivity.

§ 141.26 Monitoring frequency and compliance requirements for radionuclides in community 

water systems.

§ 141.27 Alternate analytical techniques.

§ 141.28 Certified laboratories.

§ 141.29 Monitoring of consecutive public water systems.

Appendix A to Subpart C of Part 141—Alternative Testing Methods Approved for Analyses 

Under the Safe Drinking Water Act

Subpart D—Reporting and Recordkeeping

§ 141.31 Reporting requirements.

§ 141.32 [Reserved]

§ 141.33 Record maintenance.

§ 141.34 [Reserved]

§ 141.35 Reporting for unregulated contaminant monitoring results.

Subpart E—Special Regulations, Including Monitoring Regulations and Prohibition on 

Lead Use

§ 141.40 Monitoring requirements for unregulated contaminants.

§ 141.41 Special monitoring for sodium.

§ 141.42 Special monitoring for corrosivity characteristics.

§ 141.43 Prohibition on use of lead pipes, solder, and flux.

Subpart F—Maximum Contaminant Level Goals and Maximum Residual Disinfectant 

Level Goals

§ 141.50 Maximum contaminant level goals for organic contaminants.

§ 141.51 Maximum contaminant level goals for inorganic contaminants.

§ 141.52 Maximum contaminant level goals for microbiological contaminants.

§ 141.53 Maximum contaminant level goals for disinfection byproducts.

§ 141.54 Maximum residual disinfectant level goals for disinfectants.

§ 141.55 Maximum contaminant level goals for radionuclides.

Subpart G—National Primary Drinking Water Regulations: Maximum Contaminant 

Levels and Maximum Residual Disinfectant Levels

§ 141.60 Effective dates.

§ 141.61 Maximum contaminant levels for organic contaminants.

§ 141.62 Maximum contaminant levels for inorganic contaminants.

§ 141.63 Maximum contaminant levels (MCLs) for microbiological contaminants.

§ 141.64 Maximum contaminant levels for disinfection byproducts.

§ 141.65 Maximum residual disinfectant levels.

§ 141.66 Maximum contaminant levels for radionuclides.

Subpart H—Filtration and Disinfection

§ 141.70 General requirements.

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§ 141.71 Criteria for avoiding filtration.

§ 141.72 Disinfection.

§ 141.73 Filtration.

§ 141.74 Analytical and monitoring requirements.

§ 141.75 Reporting and recordkeeping requirements.

§ 141.76 Recycle provisions.

Subpart I—Control of Lead and Copper

§ 141.80 General requirements.

§ 141.81 Applicability of corrosion control treatment steps to small, medium-size and large 

water systems.

§ 141.82 Description of corrosion control treatment requirements.

§ 141.83 Source water treatment requirements.

§ 141.84 Lead service line replacement requirements.

§ 141.85 Public education and supplemental monitoring requirements.

§ 141.86 Monitoring requirements for lead and copper in tap water.

§ 141.87 Monitoring requirements for water quality parameters.

§ 141.88 Monitoring requirements for lead and copper in source water.

§ 141.89 Analytical methods.

§ 141.90 Reporting requirements.

§ 141.91 Recordkeeping requirements.

Subpart J—Use of Non-Centralized Treatment Devices

§ 141.100 Criteria and procedures for public water systems using point-of-entry devices.

§ 141.101 Use of bottled water.

Subpart K—Treatment Techniques

§ 141.110 General requirements.

§ 141.111 Treatment techniques for acrylamide and epichlorohydrin.

Subpart L—Disinfectant Residuals, Disinfection Byproducts, and Disinfection 

Byproduct Precursors

§ 141.130 General requirements.

§ 141.131 Analytical requirements.

§ 141.132 Monitoring requirements.

§ 141.133 Compliance requirements.

§ 141.134 Reporting and recordkeeping requirements.

§ 141.135 Treatment technique for control of disinfection byproduct (DBP) precursors.

Subparts M–N [Reserved]

Subpart O—Consumer Confidence Reports

§ 141.151 Purpose and applicability of this subpart.

§ 141.152 Effective dates.

§ 141.153 Content of the reports.

§ 141.154 Required additional health information.

§ 141.155 Report delivery and recordkeeping.

Appendix A to Subpart O of Part 141—Regulated Contaminants

Subpart P—Enhanced Filtration and Disinfection—Systems Serving 10,000 or More 

People

§ 141.170 General requirements.

§ 141.171 Criteria for avoiding filtration.

§ 141.172 Disinfection profiling and benchmarking.

§ 141.173 Filtration.

§ 141.174 Filtration sampling requirements.

§ 141.175 Reporting and recordkeeping requirements.

Subpart Q—Public Notification of Drinking Water Violations

§ 141.201 General public notification requirements.

§ 141.202 Tier 1 Public Notice —Form, manner, and frequency of notice.

§ 141.203 Tier 2 Public Notice —Form, manner, and frequency of notice.

§ 141.204 Tier 3 Public Notice —Form, manner, and frequency of notice.

§ 141.205 Content of the public notice.

§ 141.206 Notice to new billing units or new customers.

§ 141.207 Special notice of the availability of unregulated contaminant monitoring results.

§ 141.208 Special notice for exceedance of the SMCL for fluoride.

§ 141.209 Special notice for nitrate exceedances above MCL by non-community water 

systems (NCWS), where granted permission by the primacy agency under §141.11(d)

§ 141.210 Notice by primacy agency on behalf of the public water system.

§ 141.211 Special notice for repeated failure to conduct monitoring of the source water for 

Cryptosporidium and for failure to determine bin classification or mean Cryptosporidium level.

Appendix A to Subpart Q of Part 141—NPDWR Violations and Other Situations Requiring 

Public Notice1

Appendix B to Subpart Q of Part 141—Standard Health Effects Language for Public 

Notification

Appendix C to Subpart Q of Part 141—List of Acronyms Used in Public Notification 

Regulation

Subpart R [Reserved]

Subpart S—Ground Water Rule

§ 141.400 General requirements and applicability.

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§ 141.401 Sanitary surveys for ground water systems.

§ 141.402 Ground water source microbial monitoring and analytical methods.

§ 141.403 Treatment technique requirements for ground water systems.

§ 141.404 Treatment technique violations for ground water systems.

§ 141.405 Reporting and recordkeeping for ground water systems.

Subpart T—Enhanced Filtration and Disinfection—Systems Serving Fewer Than 10,000 

People

General Requirements

§ 141.500 General requirements.

§ 141.501 Who is subject to the requirements of subpart T?

§ 141.502 When must my system comply with these requirements?

§ 141.503 What does subpart T require?

Finished Water Reservoirs

§ 141.510 Is my system subject to the new finished water reservoir requirements?

§ 141.511 What is required of new finished water reservoirs?

Additional Watershed Control Requirements for Unfiltered Systems

§ 141.520 Is my system subject to the updated watershed control requirements?

§ 141.521 What updated watershed control requirements must my unfiltered system 

implement to continue to avoid filtration?

§ 141.522 How does the State determine whether my system's watershed control 

requirements are adequate?

Disinfection Profile

§ 141.530 What is a disinfection profile and who must develop one?

§ 141.531 What criteria must a State use to determine that a profile is unnecessary?

§ 141.532 How does my system develop a disinfection profile and when must it begin?

§ 141.533 What data must my system collect to calculate a disinfection profile?

§ 141.534 How does my system use this data to calculate an inactivation ratio?

§ 141.535 What if my system uses chloramines, ozone, or chlorine dioxide for primary 

disinfection?

§ 141.536 My system has developed an inactivation ratio; what must we do now?

Disinfection Benchmark

§ 141.540 Who has to develop a disinfection benchmark?

§ 141.541 What are significant changes to disinfection practice?

§ 141.542 What must my system do if we are considering a significant change to disinfection 

practices?

§ 141.543 How is the disinfection benchmark calculated?

§ 141.544 What if my system uses chloramines, ozone, or chlorine dioxide for primary 

disinfection?

Combined Filter Effluent Requirements

§ 141.550 Is my system required to meet subpart T combined filter effluent turbidity limits?

§ 141.551 What strengthened combined filter effluent turbidity limits must my system meet?

§ 141.552 My system consists of “alternative filtration” and is required to conduct a 

demonstration—what is required of my system and how does the State establish my turbidity 

limits?

§ 141.553 My system practices lime softening—is there any special provision regarding my 

combined filter effluent?

Individual Filter Turbidity Requirements

§ 141.560 Is my system subject to individual filter turbidity requirements?

§ 141.561 What happens if my system's turbidity monitoring equipment fails?

§ 141.562 My system only has two or fewer filters—is there any special provision regarding 

individual filter turbidity monitoring?

§ 141.563 What follow-up action is my system required to take based on continuous turbidity 

monitoring?

§ 141.564 My system practices lime softening—is there any special provision regarding my 

individual filter turbidity monitoring?

Reporting and Recordkeeping Requirements

§ 141.570 What does subpart T require that my system report to the State?

§ 141.571 What records does subpart T require my system to keep?

Subpart U—Initial Distribution System Evaluations

§ 141.600 General requirements.

§ 141.601 Standard monitoring.

§ 141.602 System specific studies.

§ 141.603 40/30 certification.

§ 141.604 Very small system waivers.

§ 141.605 Subpart V compliance monitoring location recommendations.

Subpart V—Stage 2 Disinfection Byproducts Requirements

§ 141.620 General requirements.

§ 141.621 Routine monitoring.

§ 141.622 Subpart V monitoring plan.

§ 141.623 Reduced monitoring.

§ 141.624 Additional requirements for consecutive systems.

§ 141.625 Conditions requiring increased monitoring.

§ 141.626 Operational evaluation levels.

§ 141.627 Requirements for remaining on reduced TTHM and HAA5 monitoring based on 

subpart L results.

§ 141.628 Requirements for remaining on increased TTHM and HAA5 monitoring based on 

subpart L results.

§ 141.629 Reporting and recordkeeping requirements.

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Subpart W—Enhanced Treatment forCryptosporidium

General Requirements

§ 141.700 General requirements.

Source Water Monitoring Requirements

§ 141.701 Source water monitoring.

§ 141.702 Sampling schedules.

§ 141.703 Sampling locations.

§ 141.704 Analytical methods.

§ 141.705 Approved laboratories.

§ 141.706 Reporting source water monitoring results.

§ 141.707 Grandfathering previously collected data.

Disinfection Profiling and Benchmarking Requirements

§ 141.708 Requirements when making a significant change in disinfection practice.

§ 141.709 Developing the disinfection profile and benchmark.

Treatment Technique Requirements

§ 141.710 Bin classification for filtered systems.

§ 141.711 Filtered system additional Cryptosporidium treatment requirements.

§ 141.712 Unfiltered system Cryptosporidium treatment requirements.

§ 141.713 Schedule for compliance with Cryptosporidium treatment requirements.

§ 141.714 Requirements for uncovered finished water storage facilities.

Requirements for Microbial Toolbox Components

§ 141.715 Microbial toolbox options for meeting Cryptosporidium treatment requirements.

§ 141.716 Source toolbox components.

§ 141.717 Pre-filtration treatment toolbox components.

§ 141.718 Treatment performance toolbox components.

§ 141.719 Additional filtration toolbox components.

§ 141.720 Inactivation toolbox components.

Reporting and Recordkeeping Requirements

§ 141.721 Reporting requirements.

§ 141.722 Recordkeeping requirements.

Requirements for Sanitary Surveys Performed by EPA

§ 141.723 Requirements to respond to significant deficiencies identified in sanitary surveys 

performed by EPA.

Subpart X—Aircraft Drinking Water Rule

§ 141.800 Applicability and compliance date.

§ 141.801 Definitions.

§ 141.802 Coliform sampling plan.

§ 141.803 Coliform sampling.

§ 141.804 Aircraft water system operations and maintenance plan.

§ 141.805 Notification to passengers and crew.

§ 141.806 Reporting requirements.

§ 141.807 Recordkeeping requirements.

§ 141.808 Audits and inspections.

§ 141.809 Supplemental treatment.

§ 141.810 Violations.

Authority: 42 U.S.C. 300f, 300g–1, 300g–2, 300g–3, 300g–4, 300g–5, 300g–6, 300j–4, 

300j–9, and 300j–11. 

Source: 40 FR 59570, Dec. 24, 1975, unless otherwise noted. 

Editorial Note: Nomenclature changes to part 141 appear at 69 FR 18803, Apr. 9, 2004. 

Note: For community water systems serving 75,000 or more persons, monitoring must begin 1 

year following promulation and the effective date of the MCL is 2 years following 

promulgation. For community water systems serving 10,000 to 75,000 persons, monitoring 

must begin within 3 years from the date of promulgation and the effective date of the MCL is 4 

years from the date of promulgation. Effective immediately, systems that plan to make 

significant modifications to their treatment processes for the purpose of complying with the 

TTHM MCL are required to seek and obtain State approval of their treatment modification 

plans. This note affects §§141.2, 141.6, 141.12, 141.24 and 141.30. For additional information 

see 44 FR 68641, Nov. 29, 1979.

Subpart A—General 

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§ 141.1 Applicability. 

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This part establishes primary drinking water regulations pursuant to section 1412 of the Public Health 

Service Act, as amended by the Safe Drinking Water Act (Pub. L. 93–523); and related regulations 

applicable to public water systems. 

§ 141.2 Definitions. 

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As used in this part, the term: 

Act means the Public Health Service Act, as amended by the Safe Drinking Water Act, Public Law 93–

523. 

Action level, is the concentration of lead or copper in water specified in §141.80(c) which determines, in 

some cases, the treatment requirements contained in subpart I of this part that a water system is 

required to complete. 

Bag filters are pressure-driven separation devices that remove particulate matter larger than 1 

micrometer using an engineered porous filtration media. They are typically constructed of a non-rigid, 

fabric filtration media housed in a pressure vessel in which the direction of flow is from the inside of the 

bag to outside. 

Bank filtration is a water treatment process that uses a well to recover surface water that has naturally 

infiltrated into ground water through a river bed or bank(s). Infiltration is typically enhanced by the 

hydraulic gradient imposed by a nearby pumping water supply or other well(s). 

Best available technology or BAT means the best technology, treatment techniques, or other means 

which the Administrator finds, after examination for efficacy under field conditions and not solely under 

laboratory conditions, are available (taking cost into consideration). For the purposes of setting MCLs for 

synthetic organic chemicals, any BAT must be at least as effective as granular activated carbon. 

Cartridge filters are pressure-driven separation devices that remove particulate matter larger than 1 

micrometer using an engineered porous filtration media. They are typically constructed as rigid or semirigid, self-supporting filter elements housed in pressure vessels in which flow is from the outside of the 

cartridge to the inside. 

Coagulation means a process using coagulant chemicals and mixing by which colloidal and suspended 

materials are destabilized and agglomerated into flocs. 

Combined distribution system is the interconnected distribution system consisting of the distribution 

systems of wholesale systems and of the consecutive systems that receive finished water. 

Community water system means a public water system which serves at least 15 service connections 

used by year-round residents or regularly serves at least 25 year-round residents. 

Compliance cycle means the nine-year calendar year cycle during which public water systems must 

monitor. Each compliance cycle consists of three three-year compliance periods. The first calendar year 

cycle begins January 1, 1993 and ends December 31, 2001; the second begins January 1, 2002 and 

ends December 31, 2010; the third begins January 1, 2011 and ends December 31, 2019. 

Compliance period means a three-year calendar year period within a compliance cycle. Each 

compliance cycle has three three-year compliance periods. Within the first compliance cycle, the first 

compliance period runs from January 1, 1993 to December 31, 1995; the second from January 1, 1996 

to December 31, 1998; the third from January 1, 1999 to December 31, 2001. 

Comprehensive performance evaluation (CPE) is a thorough review and analysis of a treatment plant's 

performance-based capabilities and associated administrative, operation and maintenance practices. It 

is conducted to identify factors that may be adversely impacting a plant's capability to achieve 

compliance and emphasizes approaches that can be implemented without significant capital 

improvements. For purpose of compliance with subparts P and T of this part, the comprehensive 

performance evaluation must consist of at least the following components: Assessment of plant 

performance; evaluation of major unit processes; identification and prioritization of performance limiting 

factors; assessment of the applicability of comprehensive technical assistance; and preparation of a 

CPE report. 

Confluent growth means a continuous bacterial growth covering the entire filtration area of a membrane 

filter, or a portion thereof, in which bacterial colonies are not discrete. 

Consecutive system is a public water system that receives some or all of its finished water from one or 

more wholesale systems. Delivery may be through a direct connection or through the distribution system 

of one or more consecutive systems. 

Contaminant means any physical, chemical, biological, or radiological substance or matter in water. 

Conventional filtration treatment means a series of processes including coagulation, flocculation, 

sedimentation, and filtration resulting in substantial particulate removal. 

Corrosion inhibitor means a substance capable of reducing the corrosivity of water toward metal 

plumbing materials, especially lead and copper, by forming a protective film on the interior surface of 

those materials. 

CT or CTcalc is the product of “residual disinfectant concentration” (C) in mg/1 determined before or at 

the first customer, and the corresponding “disinfectant contact time” (T) in minutes, i.e. , “C” x “T”. If a 

public water system applies disinfectants at more than one point prior to the first customer, it must 

determine the CT of each disinfectant sequence before or at the first customer to determine the total 

percent inactivation or “total inactivation ratio.” In determining the total inactivation ratio, the public water 

system must determine the residual disinfectant concentration of each disinfection sequence and 

corresponding contact time before any subsequent disinfection application point(s). “CT99.9” is the CT 

value required for 99.9 percent (3–log) inactivation of Giardia lamblia cysts. CT99.9for a variety of 

disinfectants and conditions appear in tables 1.1–1.6, 2.1, and 3.1 of §141.74(b)(3). 

is the inactivation ratio. The sum of the inactivation ratios, or total inactivation ratio shown as 

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is calculated by adding together the inactivation ratio for each disinfection sequence. A total inactivation 

ratio equal to or greater than 1.0 is assumed to provide a 3-log inactivation of Giardia lamblia cysts. 

Diatomaceous earth filtration means a process resulting in substantial particulate removal in which (1) a 

precoat cake of diatomaceous earth filter media is deposited on a support membrance (septum), and (2) 

while the water is filtered by passing through the cake on the septum, additional filter media known as 

body feed is continuously added to the feed water to maintain the permeability of the filter cake. 

Direct filtration means a series of processes including coagulation and filtration but excluding 

sedimentation resulting in substantial particulate removal. 

Disinfectant means any oxidant, including but not limited to chlorine, chlorine dioxide, chloramines, and 

ozone added to water in any part of the treatment or distribution process, that is intended to kill or 

inactivate pathogenic microorganisms. 

Disinfectant contact time (“T” in CT calculations) means the time in minutes that it takes for water to 

move from the point of disinfectant application or the previous point of disinfectant residual 

measurement to a point before or at the point where residual disinfectant concentration (“C”) is 

measured. Where only one “C” is measured, “T” is the time in minutes that it takes for water to move 

from the point of disinfectant application to a point before or at where residual disinfectant concentration 

(“C”) is measured. Where more than one “C” is measured, “T” is (a) for the first measurement of “C”, the 

time in minutes that it takes for water to move from the first or only point of disinfectant application to a 

point before or at the point where the first “C” is measured and (b) for subsequent measurements of “C”, 

the time in minutes that it takes for water to move from the previous “C” measurement point to the “C” 

measurement point for which the particular “T” is being calculated. Disinfectant contact time in pipelines 

must be calculated based on “plug flow” by dividing the internal volume of the pipe by the maximum 

hourly flow rate through that pipe. Disinfectant contact time within mixing basins and storage reservoirs 

must be determined by tracer studies or an equivalent demonstration. 

Disinfection means a process which inactivates pathogenic organisms in water by chemical oxidants or 

equivalent agents. 

Disinfection profile is a summary of Giardia lamblia inactivation through the treatment plant. The 

procedure for developing a disinfection profile is contained in §141.172 (Disinfection profiling and 

benchmarking) in subpart P and §§141.530–141.536 (Disinfection profile) in subpart T of this part. 

Domestic or other non-distribution system plumbing problem means a coliform contamination problem in 

a public water system with more than one service connection that is limited to the specific service 

connection from which the coliform-positive sample was taken. 

Dose equivalent means the product of the absorbed dose from ionizing radiation and such factors as 

account for differences in biological effectiveness due to the type of radiation and its distribution in the 

body as specified by the International Commission on Radiological Units and Measurements (ICRU). 

Dual sample set is a set of two samples collected at the same time and same location, with one sample 

analyzed for TTHM and the other sample analyzed for HAA5. Dual sample sets are collected for the 

purposes of conducting an IDSE under subpart U of this part and determining compliance with the 

TTHM and HAA5 MCLs under subpart V of this part. 

Effective corrosion inhibitor residual, for the purpose of subpart I of this part only, means a concentration 

sufficient to form a passivating film on the interior walls of a pipe. 

Enhanced coagulation means the addition of sufficient coagulant for improved removal of disinfection 

byproduct precursors by conventional filtration treatment. 

Enhanced softening means the improved removal of disinfection byproduct precursors by precipitative 

softening. 

Filter profile is a graphical representation of individual filter performance, based on continuous turbidity 

measurements or total particle counts versus time for an entire filter run, from startup to backwash 

inclusively, that includes an assessment of filter performance while another filter is being backwashed. 

Filtration means a process for removing particulate matter from water by passage through porous media. 

Finished water is water that is introduced into the distribution system of a public water system and is 

intended for distribution and consumption without further treatment, except as treatment necessary to 

maintain water quality in the distribution system (e.g., booster disinfection, addition of corrosion control 

chemicals). 

First draw sample means a one-liter sample of tap water, collected in accordance with §141.86(b)(2), 

that has been standing in plumbing pipes at least 6 hours and is collected without flushing the tap. 

Flocculation means a process to enhance agglomeration or collection of smaller floc particles into larger, 

more easily settleable particles through gentle stirring by hydraulic or mechanical means. 

Flowing stream is a course of running water flowing in a definite channel. 

GAC10 means granular activated carbon filter beds with an empty-bed contact time of 10 minutes based 

on average daily flow and a carbon reactivation frequency of every 180 days, except that the reactivation 

frequency for GAC10 used as a best available technology for compliance with subpart V MCLs under 

§141.64(b)(2) shall be 120 days. 

GAC20 means granular activated carbon filter beds with an empty-bed contact time of 20 minutes based 

on average daily flow and a carbon reactivation frequency of every 240 days. 

Ground water under the direct influence of surface water (GWUDI) means any water beneath the 

surface of the ground with significant occurrence of insects or other macroorganisms, algae, or largediameter pathogens such as Giardia lamblia or Cryptosporidium, or significant and relatively rapid shifts 

in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to 

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climatological or surface water conditions. Direct influence must be determined for individual sources in 

accordance with criteria established by the State. The State determination of direct influence may be 

based on site-specific measurements of water quality and/or documentation of well construction 

characteristics and geology with field evaluation. 

Gross alpha particle activity means the total radioactivity due to alpha particle emission as inferred from 

measurements on a dry sample. 

Gross beta particle activity means the total radioactivity due to beta particle emission as inferred from 

measurements on a dry sample. 

Haloacetic acids (five) (HAA5) mean the sum of the concentrations in milligrams per liter of the 

haloacetic acid compounds (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, 

monobromoacetic acid, and dibromoacetic acid), rounded to two significant figures after addition. 

Halogen means one of the chemical elements chlorine, bromine or iodine. 

Initial compliance period means the first full three-year compliance period which begins at least 18 

months after promulgation, except for contaminants listed at §141.61(a) (19)–(21), (c) (19)–(33), and 

§141.62(b) (11)–(15), initial compliance period means the first full three-year compliance period after 

promulgation for systems with 150 or more service connections (January 1993–December 1995), and 

first full three-year compliance period after the effective date of the regulation (January 1996–December 

1998) for systems having fewer than 150 service connections. 

Lake/reservoir refers to a natural or man made basin or hollow on the Earth's surface in which water 

collects or is stored that may or may not have a current or single direction of flow. 

Large water system, for the purpose of subpart I of this part only, means a water system that serves 

more than 50,000 persons. 

Lead service line means a service line made of lead which connects the water main to the building inlet 

and any lead pigtail, gooseneck or other fitting which is connected to such lead line. 

Legionella means a genus of bacteria, some species of which have caused a type of pneumonia called 

Legionnaires Disease. 

Locational running annual average (LRAA) is the average of sample analytical results for samples taken 

at a particular monitoring location during the previous four calendar quarters. 

Man-made beta particle and photon emitters means all radionuclides emitting beta particles and/or 

photons listed in Maximum Permissible Body Burdens and Maximum Permissible Concentration of 

Radionuclides in Air or Water for Occupational Exposure, NBS Handbook 69, except the daughter 

products of thorium–232, uranium–235 and uranium–238. 

Maximum contaminant level means the maximum permissable level of a contaminant in water which is 

delivered to any user of a public water system. 

Maximum contaminant level goal or MCLG means the maximum level of a contaminant in drinking water 

at which no known or anticipated adverse effect on the health of persons would occur, and which allows 

an adequate margin of safety. Maximum contaminant level goals are nonenforceable health goals. 

Maximum residual disinfectant level (MRDL) means a level of a disinfectant added for water treatment 

that may not be exceeded at the consumer's tap without an unacceptable possibility of adverse health 

effects. For chlorine and chloramines, a PWS is in compliance with the MRDL when the running annual 

average of monthly averages of samples taken in the distribution system, computed quarterly, is less 

than or equal to the MRDL. For chlorine dioxide, a PWS is in compliance with the MRDL when daily 

samples are taken at the entrance to the distribution system and no two consecutive daily samples 

exceed the MRDL. MRDLs are enforceable in the same manner as maximum contaminant levels under 

Section 1412 of the Safe Drinking Water Act. There is convincing evidence that addition of a disinfectant 

is necessary for control of waterborne microbial contaminants. Notwithstanding the MRDLs listed in 

§141.65, operators may increase residual disinfectant levels of chlorine or chloramines (but not chlorine 

dioxide) in the distribution system to a level and for a time necessary to protect public health to address 

specific microbiological contamination problems caused by circumstances such as distribution line 

breaks, storm runoff events, source water contamination, or cross-connections. 

Maximum residual disinfectant level goal (MRDLG) means the maximum level of a disinfectant added for 

water treatment at which no known or anticipated adverse effect on the health of persons would occur, 

and which allows an adequate margin of safety. MRDLGs are nonenforceable health goals and do not 

reflect the benefit of the addition of the chemical for control of waterborne microbial contaminants. 

Maximum Total Trihalomethane Potential (MTP) means the maximum concentration of total 

trihalomethanes produced in a given water containing a disinfectant residual after 7 days at a 

temperature of 25 °C or above. 

Medium-size water system, for the purpose of subpart I of this part only, means a water system that 

serves greater than 3,300 and less than or equal to 50,000 persons. 

Membrane filtration is a pressure or vacuum driven separation process in which particulate matter larger 

than 1 micrometer is rejected by an engineered barrier, primarily through a size-exclusion mechanism, 

and which has a measurable removal efficiency of a target organism that can be verified through the 

application of a direct integrity test. This definition includes the common membrane technologies of 

microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. 

Near the first service connection means at one of the 20 percent of all service connections in the entire 

system that are nearest the water supply treatment facility, as measured by water transport time within 

the distribution system. 

Non-community water system means a public water system that is not a community water system. A 

non-community water system is either a “transient non-community water system (TWS)” or a “nontransient non-community water system (NTNCWS).” 

Non-transient non-community water system or NTNCWS means a public water system that is not a 

community water system and that regularly serves at least 25 of the same persons over 6 months per 

year. 

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Optimal corrosion control treatment, for the purpose of subpart I of this part only, means the corrosion 

control treatment that minimizes the lead and copper concentrations at users' taps while insuring that the 

treatment does not cause the water system to violate any national primary drinking water regulations. 

Performance evaluation sample means a reference sample provided to a laboratory for the purpose of 

demonstrating that the laboratory can successfully analyze the sample within limits of performance 

specified by the Agency. The true value of the concentration of the reference material is unknown to the 

laboratory at the time of the analysis. 

Person means an individual; corporation; company; association; partnership; municipality; or State, 

Federal, or tribal agency. 

Picocurie (pCi) means the quantity of radioactive material producing 2.22 nuclear transformations per 

minute. 

Plant intake refers to the works or structures at the head of a conduit through which water is diverted 

from a source (e.g., river or lake) into the treatment plant. 

Point of disinfectant application is the point where the disinfectant is applied and water downstream of 

that point is not subject to recontamination by surface water runoff. 

Point-of-entry treatment device (POE) is a treatment device applied to the drinking water entering a 

house or building for the purpose of reducing contaminants in the drinking water distributed throughout 

the house or building. 

Point-of-use treatment device (POU) is a treatment device applied to a single tap used for the purpose of 

reducing contaminants in drinking water at that one tap. 

Presedimentation is a preliminary treatment process used to remove gravel, sand and other particulate 

material from the source water through settling before the water enters the primary clarification and 

filtration processes in a treatment plant. 

Public water system means a system for the provision to the public of water for human consumption 

through pipes or, after August 5, 1998, other constructed conveyances, if such system has at least 

fifteen service connections or regularly serves an average of at least twenty-five individuals daily at least 

60 days out of the year. Such term includes: any collection, treatment, storage, and distribution facilities 

under control of the operator of such system and used primarily in connection with such system; and any 

collection or pretreatment storage facilities not under such control which are used primarily in connection 

with such system. Such term does not include any “special irrigation district.” A public water system is 

either a “community water system” or a “noncommunity water system.” 

Rem means the unit of dose equivalent from ionizing radiation to the total body or any internal organ or 

organ system. A “millirem (mrem)” is 1/1000 of a rem. 

Repeat compliance period means any subsequent compliance period after the initial compliance period. 

Residual disinfectant concentration (“C” in CT calculations) means the concentration of disinfectant 

measured in mg/l in a representative sample of water. 

Sanitary survey means an onsite review of the water source, facilities, equipment, operation and 

maintenance of a public water system for the purpose of evaluating the adequacy of such source, 

facilities, equipment, operation and maintenance for producing and distributing safe drinking water. 

Sedimentation means a process for removal of solids before filtration by gravity or separation. 

Service connection, as used in the definition of public water system, does not include a connection to a 

system that delivers water by a constructed conveyance other than a pipe if: 

(1) The water is used exclusively for purposes other than residential uses (consisting of drinking, 

bathing, and cooking, or other similar uses); 

(2) The State determines that alternative water to achieve the equivalent level of public health protection 

provided by the applicable national primary drinking water regulation is provided for residential or similar 

uses for drinking and cooking; or 

(3) The State determines that the water provided for residential or similar uses for drinking, cooking, and 

bathing is centrally treated or treated at the point of entry by the provider, a pass-through entity, or the 

user to achieve the equivalent level of protection provided by the applicable national primary drinking 

water regulations. 

Service line sample means a one-liter sample of water collected in accordance with §141.86(b)(3), that 

has been standing for at least 6 hours in a service line. 

Single family structure, for the purpose of subpart I of this part only, means a building constructed as a 

single-family residence that is currently used as either a residence or a place of business. 

Slow sand filtration means a process involving passage of raw water through a bed of sand at low 

velocity (generally less than 0.4 m/h) resulting in substantial particulate removal by physical and 

biological mechanisms. 

Small water system, for the purpose of subpart I of this part only, means a water system that serves 

3,300 persons or fewer. 

Special irrigation district means an irrigation district in existence prior to May 18, 1994 that provides 

primarily agricultural service through a piped water system with only incidental residential or similar use 

where the system or the residential or similar users of the system comply with the exclusion provisions in 

section 1401(4)(B)(i)(II) or (III). 

Standard sample means the aliquot of finished drinking water that is examined for the presence of 

coliform bacteria. 

State means the agency of the State or Tribal government which has jurisdiction over public water 

systems. During any period when a State or Tribal government does not have primary enforcement 

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responsibility pursuant to section 1413 of the Act, the term “State” means the Regional Administrator, 

U.S. Environmental Protection Agency. 

Subpart H systems means public water systems using surface water or ground water under the direct 

influence of surface water as a source that are subject to the requirements of subpart H of this part. 

Supplier of water means any person who owns or operates a public water system. 

Surface water means all water which is open to the atmosphere and subject to surface runoff. 

SUVA means Specific Ultraviolet Absorption at 254 nanometers (nm), an indicator of the humic content 

of water. It is a calculated parameter obtained by dividing a sample's ultraviolet absorption at a 

wavelength of 254 nm (UV254) (in m=1 ) by its concentration of dissolved organic carbon (DOC) (in 

mg/L). 

System with a single service connection means a system which supplies drinking water to consumers 

via a single service line. 

Too numerous to count means that the total number of bacterial colonies exceeds 200 on a 47-mm 

diameter membrane filter used for coliform detection. 

Total Organic Carbon (TOC) means total organic carbon in mg/L measured using heat, oxygen, 

ultraviolet irradiation, chemical oxidants, or combinations of these oxidants that convert organic carbon 

to carbon dioxide, rounded to two significant figures. 

Total trihalomethanes (TTHM) means the sum of the concentration in milligrams per liter of the 

trihalomethane compounds (trichloromethane [chloroform], dibromochloromethane, 

bromodichloromethane and tribromomethane [bromoform]), rounded to two significant figures. 

Transient non-community water system or TWS means a non-community water system that does not 

regularly serve at least 25 of the same persons over six months per year. 

Trihalomethane (THM) means one of the family of organic compounds, named as derivatives of 

methane, wherein three of the four hydrogen atoms in methane are each substituted by a halogen atom 

in the molecular structure. 

Two-stage lime softening is a process in which chemical addition and hardness precipitation occur in 

each of two distinct unit clarification processes in series prior to filtration. 

Uncovered finished water storage facility is a tank, reservoir, or other facility used to store water that will 

undergo no further treatment to reduce microbial pathogens except residual disinfection and is directly 

open to the atmosphere. 

Virus means a virus of fecal origin which is infectious to humans by waterborne transmission. 

Waterborne disease outbreak means the significant occurrence of acute infectious illness, 

epidemiologically associated with the ingestion of water from a public water system which is deficient in 

treatment, as determined by the appropriate local or State agency. 

Wholesale system is a public water system that treats source water as necessary to produce finished 

water and then delivers some or all of that finished water to another public water system. Delivery may 

be through a direct connection or through the distribution system of one or more consecutive systems. 

[40 FR 59570, Dec. 24, 1975] 

Editorial Note: For Federal Register citations affecting §141.2, see the List of CFR Sections Affected, 

which appears in the Finding Aids section of the printed volume and at www.fdsys.gov. 

§ 141.3 Coverage. 

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This part shall apply to each public water system, unless the public water system meets all of the 

following conditions: 

(a) Consists only of distribution and storage facilities (and does not have any collection and treatment 

facilities); 

(b) Obtains all of its water from, but is not owned or operated by, a public water system to which such 

regulations apply: 

(c) Does not sell water to any person; and 

(d) Is not a carrier which conveys passengers in interstate commerce. 

§ 141.4 Variances and exemptions. 

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(a) Variances or exemptions from certain provisions of these regulations may be granted pursuant to 

sections 1415 and 1416 of the Act and subpart K of part 142 of this chapter (for small system variances) 

by the entity with primary enforcement responsibility, except that variances or exemptions from the MCL 

for total coliforms and variances from any of the treatment technique requirements of subpart H of this 

part may not be granted. 

(b) EPA has stayed the effective date of this section relating to the total coliform MCL of §141.63(a) for 

systems that demonstrate to the State that the violation of the total coliform MCL is due to a persistent 

growth of total coliforms in the distribution system rather than fecal or pathogenic contamination, a 

treatment lapse or deficiency, or a problem in the operation or maintenance of the distribution system. 

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[54 FR 27562, June 29, 1989, as amended at 56 FR 1557, Jan. 15, 1991; 63 FR 43846, Aug. 14, 1998] 

§ 141.5 Siting requirements. 

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Before a person may enter into a financial commitment for or initiate construction of a new public water 

system or increase the capacity of an existing public water system, he shall notify the State and, to the 

extent practicable, avoid locating part or all of the new or expanded facility at a site which: 

(a) Is subject to a significant risk from earthquakes, floods, fires or other disasters which could cause a 

breakdown of the public water system or a portion thereof; or 

(b) Except for intake structures, is within the floodplain of a 100–year flood or is lower than any recorded 

high tide where appropriate records exist. The U.S. Environmental Protection Agency will not seek to 

override land use decisions affecting public water systems siting which are made at the State or local 

government levels. 

§ 141.6 Effective dates. 

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(a) Except as provided in paragraphs (b) through (k) of this section, and in §141.80(a)(2), the regulations 

set forth in this part shall take effect on June 24, 1977. 

(b) The regulations for total trihalomethanes set forth in §141.12(c) shall take effect 2 years after the 

date of promulgation of these regulations for community water systems serving 75,000 or more 

individuals, and 4 years after the date of promulgation for communities serving 10,000 to 74,999 

individuals. 

(c) The regulations set forth in §§141.11(d); 141.21(a), (c) and (i); 141.22(a) and (e); 141.23(a)(3) and 

(a)(4); 141.23(f); 141.24(e) and (f); 141.25(e); 141.27(a); 141.28(a) and (b); 141.31(a), (d) and (e); 

141.32(b)(3); and 141.32(d) shall take effect immediately upon promulgation. 

(d) The regulations set forth in §141.41 shall take effect 18 months from the date of promulgation. 

Suppliers must complete the first round of sampling and reporting within 12 months following the 

effective date. 

(e) The regulations set forth in §141.42 shall take effect 18 months from the date of promulgation. All 

requirements in §141.42 must be completed within 12 months following the effective date. 

(f) The regulations set forth in §141.11(c) and §141.23(g) are effective May 2, 1986. Section 141.23(g)

(4) is effective October 2, 1987. 

(g) The regulations contained in §141.6, paragraph (c) of the table in 141.12, and 141.62(b)(1) are 

effective July 1, 1991. The regulations contained in §§141.11(b), 141.23, 141.24, 142.57(b), 143.4(b)

(12) and (b)(13), are effective July 30, 1992. The regulations contained in the revisions to §§141.32(e) 

(16), (25) through (27) and (46); 141.61(c)(16); and 141.62(b)(3) are effective January 1, 1993. The 

effective date of regulations contained in §141.61(c) (2), (3), and (4) is postponed. 

(h) Regulations for the analytic methods listed at §141.23(k)(4) for measuring antimony, beryllium, 

cyanide, nickel, and thallium are effective August 17, 1992. Regulations for the analytic methods listed at 

§141.24(f)(16) for dichloromethane, 1,2,4-trichlorobenzene, and 1,1,2-trichloroethane are effective 

August 17, 1992. Regulations for the analytic methods listed at §141.24(h)(12) for measuring dalapon, 

dinoseb, diquat, endothall, endrin, glyphosate, oxamyl, picloram, simazine, benzo(a)pyrene, di(2-

ethylhexyl)adipate, di(2-ethylhexyl)phthalate, hexachlorobenzene, hexachlorocyclopentadiene, and 

2,3,7,8-TCDD are effective August 17, 1992. The revision to §141.12(a) promulgated on July 17, 1992 is 

effective on August 17, 1992. 

(i) [Reserved] 

(j) The arsenic maximum contaminant levels (MCL) listed in §141.62 is effective for the purpose of 

compliance on January 23, 2006. Requirements relating to arsenic set forth in §§141.23(i)(4), 141.23(k)

(3) introductory text, 141.23(k)(3)(ii), 141.51(b), 141.62(b), 141.62(b)(16), 141.62(c), 141.62(d), and 

142.62(b) revisions in Appendix A of subpart O for the consumer confidence rule, and Appendices A and 

B of subpart Q for the public notification rule are effective for the purpose of compliance on January 23, 

2006. However, the consumer confidence rule reporting requirements relating to arsenic listed in 

§141.154(b) and (f) are effective for the purpose of compliance on February 22, 2002. 

(k) Regulations set forth in §§141.23(i)(1), 141.23(i)(2), 141.24(f)(15), 141.24(f)(22), 141.24(h)(11), 

141.24(h)(20), 142.16(e), 142.16(j), and 142.16(k) are effective for the purpose of compliance on 

January 22, 2004. 

[44 FR 68641, Nov. 29, 1979, as amended at 45 FR 57342, Aug. 27, 1980; 47 FR 10998, Mar. 12, 1982; 

51 FR 11410, Apr. 2, 1986; 56 FR 30274, July 1, 1991; 57 FR 22178, May 27, 1992; 57 FR 31838, July 

17, 1992; 59 FR 34322, July 1, 1994; 61 FR 24368, May 14, 1996; 66 FR 7061, Jan. 22, 2001; 66 FR 

28350, May 22, 2001] 

Subpart B—Maximum Contaminant Levels 

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§ 141.11 Maximum contaminant levels for inorganic chemicals. 

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(a) The maximum contaminant level for arsenic applies only to community water systems. The analyses 

and determination of compliance with the 0.05 milligrams per liter maximum contaminant level for 

arsenic use the requirements of §141.23. 

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(b) The maximum contaminant level for arsenic is 0.05 milligrams per liter for community water systems 

until January 23, 2006. 

(c) [Reserved] 

(d) At the discretion of the State, nitrate levels not to exceed 20 mg/l may be allowed in a noncommunity water system if the supplier of water demonstrates to the satisfaction of the State that: 

(1) Such water will not be available to children under 6 months of age; and 

(2) The non-community water system is meeting the public notification requirements under §141.209, 

including continuous posting of the fact that nitrate levels exceed 10 mg/l and the potential health effects 

of exposure; and 

(3) Local and State public health authorities will be notified annually of nitrate levels that exceed 10 mg/l; 

and 

(4) No adverse health effects shall result. 

[40 FR 59570, Dec. 24, 1975, as amended at 45 FR 57342, Aug. 27, 1980; 47 FR 10998, Mar. 12, 1982; 

51 FR 11410, Apr. 2, 1986; 56 FR 3578, Jan. 30, 1991; 56 FR 26548, June 7, 1991; 56 FR 30274, July 

1, 1991; 56 FR 32113, July 15, 1991; 60 FR 33932, June 29, 1995; 65 FR 26022, May 4, 2000; 66 FR 

7061, Jan. 22, 2001] 

§ 141.12 [Reserved] 

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§ 141.13 Maximum contaminant levels for turbidity. 

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The maximum contaminant levels for turbidity are applicable to both community water systems and noncommunity water systems using surface water sources in whole or in part. The maximum contaminant 

levels for turbidity in drinking water, measured at a representative entry point(s) to the distribution 

system, are: 

Editorial Note: At 54 FR 27527, June 29, 1989, §141.13 was amended by adding introductory text, 

effective December 31, 1990. However, introductory text already exists. The added text follows. 

The requirements in this section apply to unfiltered systems until December 30, 1991, unless the State 

has determined prior to that date, in writing pursuant to §1412(b)(7)(C)(iii), that filtration is required. The 

requirements in this section apply to filtered systems until June 29, 1993. The requirements in this 

section apply to unfiltered systems that the State has determined, in writing pursuant to §1412(b)(7)(C)

(iii), must install filtration, until June 29, 1993, or until filtration is installed, whichever is later. 

(a) One turbidity unit (TU), as determined by a monthly average pursuant to §141.22, except that five or 

fewer turbidity units may be allowed if the supplier of water can demonstrate to the State that the higher 

turbidity does not do any of the following: 

(1) Interfere with disinfection; 

(2) Prevent maintenance of an effective disinfectant agent throughout the distribution system; or 

(3) Interfere with microbiological determinations. 

(b) Five turbidity units based on an average for two consecutive days pursuant to §141.22. 

[40 FR 59570, Dec. 24, 1975] 

Subpart C—Monitoring and Analytical Requirements 

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§ 141.21 Coliform sampling. 

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(a) Routine monitoring. (1) Public water systems must collect total coliform samples at sites which are 

representative of water throughout the distribution system according to a written sample siting plan. 

These plans are subject to State review and revision. 

(2) The monitoring frequency for total coliforms for community water systems is based on the population 

served by the system, as follows: 

Total Coliform Monitoring Frequency for Community Water Systems 

Population served Minimum number of samples per month

25 to 1,0001 1

1,001 to 2,500 2

2,501 to 3,300 3

3,301 to 4,100 4

4,101 to 4,900 5

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1Includes public water systems which have at least 15 service connections, but serve fewer than 25 

persons. 

If a community water system serving 25 to 1,000 persons has no history of total coliform contamination 

in its current configuration and a sanitary survey conducted in the past five years shows that the system 

is supplied solely by a protected groundwater source and is free of sanitary defects, the State may 

reduce the monitoring frequency specified above, except that in no case may the State reduce the 

monitoring frequency to less than one sample per quarter. The State must approve the reduced 

monitoring frequency in writing. 

(3) The monitoring frequency for total coliforms for non-community water systems is as follows: 

(i) A non-community water system using only ground water (except ground water under the direct 

influence of surface water, as defined in §141.2) and serving 1,000 persons or fewer must monitor each 

calendar quarter that the system provides water to the public, except that the State may reduce this 

monitoring frequency, in writing, if a sanitary survey shows that the system is free of sanitary defects. 

Beginning June 29, 1994, the State cannot reduce the monitoring frequency for a non-community water 

system using only ground water (except ground water under the direct influence of surface water, as 

defined in §141.2) and serving 1,000 persons or fewer to less than once/year. 

(ii) A non-community water system using only ground water (except ground water under the direct 

influence of surface water, as defined in §141.2) and serving more than 1,000 persons during any month 

must monitor at the same frequency as a like-sized community water system, as specified in paragraph 

(a)(2) of this section, except the State may reduce this monitoring frequency, in writing, for any month 

the system serves 1,000 persons or fewer. The State cannot reduce the monitoring frequency to less 

than once/year. For systems using ground water under the direct influence of surface water, paragraph 

(a)(3)(iv) of this section applies. 

(iii) A non-community water system using surface water, in total or in part, must monitor at the same 

frequency as a like-sized community water system, as specified in paragraph (a)(2) of this section, 

regardless of the number of persons it serves. 

(iv) A non-community water system using ground water under the direct influence of surface water, as 

defined in §141.2, must monitor at the same frequency as a like-sized community water system, as 

specified in paragraph (a)(2) of this section. The system must begin monitoring at this frequency 

beginning six months after the State determines that the ground water is under the direct influence of 

surface water. 

(4) The public water system must collect samples at regular time intervals throughout the month, except 

that a system which uses only ground water (except ground water under the direct influence of surface 

water, as defined in §141.2), and serves 4,900 persons or fewer, may collect all required samples on a 

single day if they are taken from different sites. 

(5) A public water system that uses surface water or ground water under the direct influence of surface 

water, as defined in §141.2, and does not practice filtration in compliance with Subpart H must collect at 

least one sample near the first service connection each day the turbidity level of the source water, 

measured as specified in §141.74(b)(2), exceeds 1 NTU. This sample must be analyzed for the 

presence of total coliforms. When one or more turbidity measurements in any day exceed 1 NTU, the 

system must collect this coliform sample within 24 hours of the first exceedance, unless the State 

determines that the system, for logistical reasons outside the system's control, cannot have the sample 

4,901 to 5,800 6

5,801 to 6,700 7

6,701 to 7,600 8

7,601 to 8,500 9

8,501 to 12,900 10

12,901 to 17,200 15

17,201 to 21,500 20

21,501 to 25,000 25

25,001 to 33,000 30

33,001 to 41,000 40

41,001 to 50,000 50

50,001 to 59,000 60

59,001 to 70,000 70

70,001 to 83,000 80

83,001 to 96,000 90

96,001 to 130,000 100

130,001 to 220,000 120

220,001 to 320,000 150

320,001 to 450,000 180

450,001 to 600,000 210

600,001 to 780,000 240

780,001 to 970,000 270

970,001 to 1,230,000 300

1,230,001 to 1,520,000 330

1,520,001 to 1,850,000 360

1,850,001 to 2,270,000 390

2,270,001 to 3,020,000 420

3,020,001 to 3,960,000 450

3,960,001 or more 480

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analyzed within 30 hours of collection. Sample results from this coliform monitoring must be included in 

determining compliance with the MCL for total coliforms in §141.63. 

(6) Special purpose samples, such as those taken to determine whether disinfection practices are 

sufficient following pipe placement, replacement, or repair, shall not be used to determine compliance 

with the MCL for total coliforms in §141.63. Repeat samples taken pursuant to paragraph (b) of this 

section are not considered special purpose samples, and must be used to determine compliance with 

the MCL for total coliforms in §141.63. 

(b) Repeat monitoring. (1) If a routine sample is total coliform-positive, the public water system must 

collect a set of repeat samples within 24 hours of being notified of the positive result. A system which 

collects more than one routine sample/month must collect no fewer than three repeat samples for each 

total coliform-positive sample found. A system which collects one routine sample/month or fewer must 

collect no fewer than four repeat samples for each total coliform-positive sample found. The State may 

extend the 24-hour limit on a case-by-case basis if the system has a logistical problem in collecting the 

repeat samples within 24 hours that is beyond its control. In the case of an extension, the State must 

specify how much time the system has to collect the repeat samples. 

(2) The system must collect at least one repeat sample from the sampling tap where the original total 

coliform-positive sample was taken, and at least one repeat sample at a tap within five service 

connections upstream and at least one repeat sample at a tap within five service connections 

downstream of the original sampling site. If a total coliform-positive sample is at the end of the 

distribution system, or one away from the end of the distribution system, the State may waive the 

requirement to collect at least one repeat sample upstream or downstream of the original sampling site. 

(3) The system must collect all repeat samples on the same day, except that the State may allow a 

system with a single service connection to collect the required set of repeat samples over a four-day 

period or to collect a larger volume repeat sample(s) in one or more sample containers of any size, as 

long as the total volume collected is at least 400 ml (300 ml for systems which collect more than one 

routine sample/month). 

(4) If one or more repeat samples in the set is total coliform-positive, the public water system must 

collect an additional set of repeat samples in the manner specified in paragraphs (b) (1)–(3) of this 

section. The additional samples must be collected within 24 hours of being notified of the positive result, 

unless the State extends the limit as provided in paragraph (b)(1) of this section. The system must 

repeat this process until either total coliforms are not detected in one complete set of repeat samples or 

the system determines that the MCL for total coliforms in §141.63 has been exceeded and notifies the 

State. 

(5) If a system collecting fewer than five routine samples/month has one or more total coliform-positive 

samples and the State does not invalidate the sample(s) under paragraph (c) of this section, it must 

collect at least five routine samples during the next month the system provides water to the public, 

except that the State may waive this requirement if the conditions of paragraph (b)(5) (i) or (ii) of this 

section are met. The State cannot waive the requirement for a system to collect repeat samples in 

paragraphs (b) (1)–(4) of this section. 

(i) The State may waive the requirement to collect five routine samples the next month the system 

provides water to the public if the State, or an agent approved by the State, performs a site visit before 

the end of the next month the system provides water to the public. Although a sanitary survey need not 

be performed, the site visit must be sufficiently detailed to allow the State to determine whether 

additional monitoring and/or any corrective action is needed. The State cannot approve an employee of 

the system to perform this site visit, even if the employee is an agent approved by the State to perform 

sanitary surveys. 

(ii) The State may waive the requirement to collect five routine samples the next month the system 

provides water to the public if the State has determined why the sample was total coliform-positive and 

establishes that the system has corrected the problem or will correct the problem before the end of the 

next month the system serves water to the public. In this case, the State must document this decision to 

waive the following month's additional monitoring requirement in writing, have it approved and signed by 

the supervisor of the State official who recommends such a decision, and make this document available 

to the EPA and public. The written documentation must describe the specific cause of the total coliformpositive sample and what action the system has taken and/or will take to correct this problem. The State 

cannot waive the requirement to collect five routine samples the next month the system provides water 

to the public solely on the grounds that all repeat samples are total coliform-negative. Under this 

paragraph, a system must still take at least one routine sample before the end of the next month it 

serves water to the public and use it to determine compliance with the MCL for total coliforms in 

§141.63, unless the State has determined that the system has corrected the contamination problem 

before the system took the set of repeat samples required in paragraphs (b) (1)–(4) of this section, and 

all repeat samples were total coliform-negative. 

(6) After a system collects a routine sample and before it learns the results of the analysis of that 

sample, if it collects another routine sample(s) from within five adjacent service connections of the initial 

sample, and the initial sample, after analysis, is found to contain total coliforms, then the system may 

count the subsequent sample(s) as a repeat sample instead of as a routine sample. 

(7) Results of all routine and repeat samples not invalidated by the State must be included in 

determining compliance with the MCL for total coliforms in §141.63. 

(c) Invalidation of total coliform samples. A total coliform-positive sample invalidated under this 

paragraph (c) does not count towards meeting the minimum monitoring requirements of this section. 

(1) The State may invalidate a total coliform-positive sample only if the conditions of paragraph (c)(1) (i), 

(ii), or (iii) of this section are met. 

(i) The laboratory establishes that improper sample analysis caused the total coliform-positive result. 

(ii) The State, on the basis of the results of repeat samples collected as required by paragraphs (b) (1) 

through (4) of this section, determines that the total coliform-positive sample resulted from a domestic or 

other non-distribution system plumbing problem. The State cannot invalidate a sample on the basis of 

repeat sample results unless all repeat sample(s) collected at the same tap as the original total coliformpositive sample are also total coliform-positive, and all repeat samples collected within five service 

connections of the original tap are total coliform-negative (e.g., a State cannot invalidate a total coliformpositive sample on the basis of repeat samples if all the repeat samples are total coliform-negative, or if 

the public water system has only one service connection). 

(iii) The State has substantial grounds to believe that a total coliform-positive result is due to a 

circumstance or condition which does not reflect water quality in the distribution system. In this case, the 

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system must still collect all repeat samples required under paragraphs (b) (1)–(4) of this section, and use 

them to determine compliance with the MCL for total coliforms in §141.63. To invalidate a total coliformpositive sample under this paragraph, the decision with the rationale for the decision must be 

documented in writing, and approved and signed by the supervisor of the State official who 

recommended the decision. The State must make this document available to EPA and the public. The 

written documentation must state the specific cause of the total coliform-positive sample, and what 

action the system has taken, or will take, to correct this problem. The State may not invalidate a total 

coliform-positive sample solely on the grounds that all repeat samples are total coliform-negative. 

(2) A laboratory must invalidate a total coliform sample (unless total coliforms are detected) if the sample 

produces a turbid culture in the absence of gas production using an analytical method where gas 

formation is examined (e.g., the Multiple-Tube Fermentation Technique), produces a turbid culture in the 

absence of an acid reaction in the Presence-Absence (P-A) Coliform Test, or exhibits confluent growth 

or produces colonies too numerous to count with an analytical method using a membrane filter (e.g., 

Membrane Filter Technique). If a laboratory invalidates a sample because of such interference, the 

system must collect another sample from the same location as the original sample within 24 hours of 

being notified of the interference problem, and have it analyzed for the presence of total coliforms. The 

system must continue to re-sample within 24 hours and have the samples analyzed until it obtains a 

valid result. The State may waive the 24-hour time limit on a case-by-case basis. 

(d) Sanitary surveys. (1)(i) Public water systems which do not collect five or more routine samples/month 

must undergo an initial sanitary survey by June 29, 1994, for community public water systems and June 

29, 1999, for non-community water systems. Thereafter, systems must undergo another sanitary survey 

every five years, except that non-community water systems using only protected and disinfected ground 

water, as defined by the State, must undergo subsequent sanitary surveys at least every ten years after 

the initial sanitary survey. The State must review the results of each sanitary survey to determine 

whether the existing monitoring frequency is adequate and what additional measures, if any, the system 

needs to undertake to improve drinking water quality. 

(ii) In conducting a sanitary survey of a system using ground water in a State having an EPA-approved 

wellhead protection program under section 1428 of the Safe Drinking Water Act, information on sources 

of contamination within the delineated wellhead protection area that was collected in the course of 

developing and implementing the program should be considered instead of collecting new information, if 

the information was collected since the last time the system was subject to a sanitary survey. 

(2) Sanitary surveys must be performed by the State or an agent approved by the State. The system is 

responsible for ensuring the survey takes place. 

(3) Sanitary surveys conducted by the State under the provisions of §142.16(o)(2) of this chapter may be 

used to meet the sanitary survey requirements of this section. 

(e) Fecal coliforms/Escherichia coli (E. coli) testing. (1) If any routine or repeat sample is total coliformpositive, the system must analyze that total coliform-positive culture medium to determine if fecal 

coliforms are present, except that the system may test for E. coli in lieu of fecal coliforms. If fecal 

coliforms or E. coli are present, the system must notify the State by the end of the day when the system 

is notified of the test result, unless the system is notified of the result after the State office is closed, in 

which case the system must notify the State before the end of the next business day. 

(2) The State has the discretion to allow a public water system, on a case-by-case basis, to forgo fecal 

coliform or E. coli testing on a total coliform-positive sample if that system assumes that the total 

coliform-positive sample is fecal coliform-positive or E. coli -positive. Accordingly, the system must notify 

the State as specified in paragraph (e)(1) of this section and the provisions of §141.63(b) apply. 

(f) Analytical methodology. (1) The standard sample volume required for total coliform analysis, 

regardless of analytical method used, is 100 ml. 

(2) Public water systems need only determine the presence or absence of total coliforms; a 

determination of total coliform density is not required. 

(3) Public water systems must conduct total coliform analyses in accordance with one of the analytical 

methods in the following table or one of the alternative methods listed in appendix A to subpart C of this 

part. 

The procedures shall be done in accordance with the documents listed below. The incorporation by 

reference of the following documents listed in footnotes 1, 6, 8, 9, 10 , 11, 13, 14 and 15 was approved 

by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of 

the documents may be obtained from the sources listed below. Information regarding obtaining these 

documents can be obtained from the Safe Drinking Water Hotline at 800–426–4791. Documents may be 

inspected at EPA's Drinking Water Docket, EPA West, 1301 Constitution Avenue, NW., EPA West, 

Room B102, Washington DC 20460 (Telephone: 202–566–2426); or at the National Archives and 

Organism Methodology12 Citation1

Total 

Coliforms2

Total Coliform Fermentation Technique3,4,5 9221A, B.

 Total Coliform Membrane Filter Technique6 9222A, B, 

C.

 Presence-Absence (P-A) Coliform Test5,7 9221D.

 ONPG-MUG Test8 9223.

 Colisure Test.9

 E*Colite®Test.10

 m-ColiBlue24®Test.11

 Readycult®Coliforms 100 Presence/Absence 

Test.13

 Membrane Filter Technique using 

Chromocult®Coliform Agar.14

 Colitag®Test.15

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Records Administration (NARA). For information on the availability of this material at NARA, call 202–

741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

1 Standard Methods for the Examination of Water and Wastewater, 18th edition (1992), 19th edition 

(1995), or 20th edition (1998). American Public Health Association, 1015 Fifteenth Street, NW., 

Washington, DC 20005. The cited methods published in any of these three editions may be used. In 

addition, the following online versions may also be used: 9221 A, B, D–99, 9222 A, B, C–97, and 9223 

B–97. Standard Methods Online are available at http://www.standardmethods.org. The year in which 

each method was approved by the Standard Methods Committee is designated by the last two digits in 

the method number. The methods listed are the only Online versions that may be used. 

2The time from sample collection to initiation of analysis may not exceed 30 hours. Systems are 

encouraged but not required to hold samples below 10 deg. C during transit. 

3Lactose broth, as commercially available, may be used in lieu of lauryl tryptose broth, if the system 

conducts at least 25 parallel tests between this medium and lauryl tryptose broth using the water 

normally tested, and this comparison demonstrates that the false-positive rate and false-negative rate for 

total coliform, using lactose broth, is less than 10 percent. 

4If inverted tubes are used to detect gas production, the media should cover these tubes at least onehalf to two-thirds after the sample is added. 

5No requirement exists to run the completed phase on 10 percent of all total coliform-positive confirmed 

tubes. 

6MI agar also may be used. Preparation and use of MI agar is set forth in the article, “New medium for 

the simultaneous detection of total coliform and Escherichia coli in water” by Brenner, K.P., et. al., 1993, 

Appl. Environ. Microbiol. 59:3534–3544. Also available from the Office of Water Resource Center (RC–

4100T), 1200 Pennsylvania Avenue, NW., Washington, DC 20460, EPA/600/J–99/225. Verification of 

colonies is not required. 

7Six-times formulation strength may be used if the medium is filter-sterilized rather than autoclaved.

8The ONPG-MUG Test is also known as the Autoanalysis Collect System.

9A description of the Colisure Test, Feb 28, 1994, may be obtained from IDEXX Laboratories, Inc., One 

IDEXX Drive, Westbrook, Maine 04092. The Colisure Test may be read after an incubation time of 24 

hours. 

10A description of the E*Colite®Test, “Presence/Absence for Coliforms and E. Coli in Water,” Dec 21, 

1997, is available from Charm Sciences, Inc., 36 Franklin Street, Malden, MA 02148–4120. 

11A description of the m-ColiBlue24®Test, Aug 17, 1999, is available from the Hach Company, 100 

Dayton Avenue, Ames, IA 50010. 

12EPA strongly recommends that laboratories evaluate the false-positive and negative rates for the 

method(s) they use for monitoring total coliforms. EPA also encourages laboratories to establish falsepositive and false-negative rates within their own laboratory and sample matrix (drinking water or source 

water) with the intent that if the method they choose has an unacceptable false-positive or negative rate, 

another method can be used. The Agency suggests that laboratories perform these studies on a 

minimum of 5% of all total coliform-positive samples, except for those methods where 

verification/confirmation is already required, e.g., the M-Endo and LES Endo Membrane Filter Tests, 

Standard Total Coliform Fermentation Technique, and Presence-Absence Coliform Test. Methods for 

establishing false-positive and negative-rates may be based on lactose fermentation, the rapid test for βgalactosidase and cytochrome oxidase, multi-test identification systems, or equivalent confirmation 

tests. False-positive and false-negative information is often available in published studies and/or from 

the manufacturer(s). 

13The Readycult®Coliforms 100 Presence/Absence Test is described in the document, 

“Readycult®Coliforms 100 Presence/Absence Test for Detection and Identification of Coliform Bacteria 

and Escherichla coli in Finished Waters”, November 2000, Version 1.0, available from EM Science (an 

affiliate of Merck KGgA, Darmstadt Germany), 480 S. Democrat Road, Gibbstown, NJ 08027–1297. 

Telephone number is (800) 222–0342, e-mail address is: adellenbusch@emscience.com. 

14Membrane Filter Technique using Chromocult®Coliform Agar is described in the document, 

“Chromocult®Coliform Agar Presence/Absence Membrane Filter Test Method for Detection and 

Identification of Coliform Bacteria and Escherichla coli in Finished Waters”, November 2000, Version 

1.0, available from EM Science (an affiliate of Merck KGgA, Darmstadt Germany), 480 S. Democrat 

Road, Gibbstown, NJ 08027–1297. Telephone number is (800) 222–0342, e-mail address is: 

adellenbusch@emscience.com. 

15Colitag®product for the determination of the presence/absence of total coliforms and E. coli is 

described in “Colitag®Product as a Test for Detection and Identification of Coliforms and E. coli Bacteria 

in Drinking Water and Source Water as Required in National Primary Drinking Water Regulations,” 

August 2001, available from CPI International, Inc., 5580 Skylane Blvd., Santa Rosa, CA, 95403, 

telephone (800) 878–7654, Fax (707) 545–7901, Internet address http://www.cpiinternational.com. 

(4) [Reserved] 

(5) Public water systems must conduct fecal coliform analysis in accordance with the following 

procedure. When the MTF Technique or Presence-Absence (PA) Coliform Test is used to test for total 

coliforms, shake the lactose-positive presumptive tube or P-A vigorously and transfer the growth with a 

sterile 3-mm loop or sterile applicator stick into brilliant green lactose bile broth and EC medium to 

determine the presence of total and fecal coliforms, respectively. For EPA-approved analytical methods 

which use a membrane filter, transfer the total coliform-positive culture by one of the following methods: 

remove the membrane containing the total coliform colonies from the substrate with a sterile forceps and 

carefully curl and insert the membrane into a tube of EC medium (the laboratory may first remove a 

small portion of selected colonies for verification), swab the entire membrane filter surface with a sterile 

cotton swab and transfer the inoculum to EC medium (do not leave the cotton swab in the EC medium), 

or inoculate individual total coliform-positive colonies into EC Medium. Gently shake the inoculated tubes 

of EC medium to insure adequate mixing and incubate in a waterbath at 44.5 ±0.2 °C for 24 ±2 hours. 

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Gas production of any amount in the inner fermentation tube of the EC medium indicates a positive fecal 

coliform test. The preparation of EC medium is described in Method 9221E (paragraph 1a) in Standard 

Methods for the Examination of Water and Wastewater, 18th edition (1992), 19th edition (1995), and 

20th edition (1998); the cited method in any one of these three editions may be used. Public water 

systems need only determine the presence or absence of fecal coliforms; a determination of fecal 

coliform density is not required. 

(6) Public water systems must conduct analysis of Escherichia coli in accordance with one of the 

following analytical methods or one of the alternative methods listed in appendix A to subpart C of this 

part. 

(i) EC medium supplemented with 50 μg/mL of 4-methylumbelliferyl-beta-D-glucuronide (MUG) (final 

concentration), as described in Method 9222G in Standard Methods for the Examination of Water and 

Wastewater, 19th edition (1995) and 20th edition (1998). Either edition may be used. Alternatively, the 

18th edition (1992) may be used if at least 10 mL of EC medium, as described in paragraph (f)(5) of this 

section, is supplemented with 50 μg/mL of MUG before autoclaving. The inner inverted fermentation 

tube may be omitted. If the 18th edition is used, apply the procedure in paragraph (f)(5) of this section 

for transferring a total coliform-positive culture to EC medium supplemented with MUG, incubate the 

tube at 44.5 ±0.2 °C for 24 ±2 hours, and then observe fluorescence with an ultraviolet light (366 nm) in 

the dark. If fluorescence is visible, E. coli are present. 

(ii) Nutrient agar supplemented with 100 μg/mL of 4-methylumbelliferyl-beta-D-glucuronide (MUG) (final 

concentration), as described in Method 9222G in Standard Methods for the Examination of Water and 

Wastewater, 19th edition (1995) and 20th edition (1998). Either edition may be used for determining if a 

total coliform-positive sample, as determined by a membrane filter technique, contains E. coli. 

Alternatively, the 18th edition (1992) may be used if the membrane filter containing a total coliformpositive colony(ies) is transferred to nutrient agar, as described in Method 9221B (paragraph 3) of 

Standard Methods (18th edition), supplemented with 100 μg/mL of MUG. If the 18th edition is used, 

incubate the agar plate at 35 °C for 4 hours and then observe the colony(ies) under ultraviolet light (366 

nm) in the dark for fluorescence. If fluorescence is visible, E. coli are present. 

(iii) Minimal Medium ONPG-MUG (MMO-MUG) Test, as set forth in the article “National Field Evaluation 

of a Defined Substrate Method for the Simultaneous Detection of Total Coliforms and Escherichia coli 

from Drinking Water: Comparison with Presence-Absence Techniques” (Edberg et al.), Applied and 

Environmental Microbiology, Volume 55, pp. 1003–1008, April 1989. (Note: The Autoanalysis Colilert 

System is an MMO-MUG test). If the MMO-MUG test is total coliform-positive after a 24-hour incubation, 

test the medium for fluorescence with a 366-nm ultraviolet light (preferably with a 6-watt lamp) in the 

dark. If fluorescence is observed, the sample is E. coli -positive. If fluorescence is questionable (cannot 

be definitively read) after 24 hours incubation, incubate the culture for an additional four hours (but not to 

exceed 28 hours total), and again test the medium for fluorescence. The MMO-MUG Test with hepes 

buffer in lieu of phosphate buffer is the only approved formulation for the detection of E. coli. 

(iv) The Colisure Test. A description of the Colisure Test may be obtained from the Millipore Corporation, 

Technical Services Department, 80 Ashby Road, Bedford, MA 01730. 

(v) The membrane filter method with MI agar, a description of which is cited in footnote 6 to the table in 

paragraph (f)(3) of this section. 

(vi) E*Colite®Test, a description of which is cited in footnote 10 to the table at paragraph (f)(3) of this 

section. 

(vii) m-ColiBlue24®Test, a description of which is cited in footnote 11 to the table in paragraph (f)(3) of 

this section. 

(viii) Readycult®Coliforms 100 Presence/Absence Test, a description of which is cited in footnote 13 to 

the table at paragraph (f)(3) of this section. 

(ix) Membrane Filter Technique using Chromocult®Coliform Agar, a description of which is cited in 

footnote 14 to the table at paragraph (f)(3) of this section. 

(x) Colitag®, a description of which is cited in footnote 15 to the table at paragraph (f)(3) of this section.

(7) As an option to paragraph (f)(6)(iii) of this section, a system with a total coliform-positive, MUGnegative, MMO-MUG test may further analyze the culture for the presence of E. coli by transferring a 0.1 

ml, 28-hour MMO-MUG culture to EC Medium + MUG with a pipet. The formulation and incubation 

conditions of EC Medium + MUG, and observation of the results are described in paragraph (f)(6)(i) of 

this section. 

(8) The following materials are incorporated by reference in this section with the approval of the Director 

of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the analytical 

methods cited in Standard Methods for the Examination of Water and Wastewater (18th, 19th, and 20th 

editions) may be obtained from the American Public Health Association et al. ; 1015 Fifteenth Street, 

NW., Washington, DC 20005–2605. Copies of the MMO-MUG Test, as set forth in the article “National 

Field Evaluation of a Defined Substrate Method for the Simultaneous Enumeration of Total Coliforms 

and Escherichia coli from Drinking Water: Comparison with the Standard Multiple Tube Fermentation 

Method” (Edberg et al. ) may be obtained from the American Water Works Association Research 

Foundation, 6666 West Quincy Avenue, Denver, CO 80235. Copies of the MMO-MUG Test as set forth 

in the article “National Field Evaluation of a Defined Substrate Method for the Simultaneous 

Enumeration of Total Coliforms and Escherichia coli from Drinking Water: Comparison with the Standard 

Multiple Tube Fermentation Method” (Edberg et al. ) may be obtained from the American Water Works 

Association Research Foundation, 6666 West Quincy Avenue, Denver, CO 80235. A description of the 

Colisure Test may be obtained from the Millipore Corp., Technical Services Department, 80 Ashby 

Road, Bedford, MA 01730. Copies may be inspected at EPA's Drinking Water Docket; 401 M St., SW.; 

Washington, DC 20460, or at the National Archives and Records Administration (NARA). For information 

on the availability of this material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

(g) Response to violation. (1) A public water system which has exceeded the MCL for total coliforms in 

§141.63 must report the violation to the State no later than the end of the next business day after it 

learns of the violation, and notify the public in accordance with subpart Q. 

(2) A public water system which has failed to comply with a coliform monitoring requirement, including 

the sanitary survey requirement, must report the monitoring violation to the State within ten days after 

the system discovers the violation, and notify the public in accordance with subpart Q. 

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[54 FR 27562, June 29, 1989] 

Editorial Note: For Federal Register citations affecting §141.21, see the List of CFR Sections 

Affected, which appears in the Finding Aids section of the printed volume and at www.fdsys.gov. 

§ 141.22 Turbidity sampling and analytical requirements. 

 top

The requirements in this section apply to unfiltered systems until December 30, 1991, unless the State 

has determined prior to that date, in writing pursuant to section 1412(b)(7)(iii), that filtration is required. 

The requirements in this section apply to filtered systems until June 29, 1993. The requirements in this 

section apply to unfiltered systems that the State has determined, in writing pursuant to section 1412(b)

(7)(C)(iii), must install filtration, until June 29, 1993, or until filtration is installed, whichever is later. 

(a) Samples shall be taken by suppliers of water for both community and non-community water systems 

at a representative entry point(s) to the water distribution system at least once per day, for the purposes 

of making turbidity measurements to determine compliance with §141.13. If the State determines that a 

reduced sampling frequency in a non-community will not pose a risk to public health, it can reduce the 

required sampling frequency. The option of reducing the turbidity frequency shall be permitted only in 

those public water systems that practice disinfection and which maintain an active residual disinfectant 

in the distribution system, and in those cases where the State has indicated in writing that no 

unreasonable risk to health existed under the circumstances of this option. Turbidity measurements shall 

be made as directed in §141.74(a)(1). 

(b) If the result of a turbidity analysis indicates that the maximum allowable limit has been exceeded, the 

sampling and measurement shall be confirmed by resampling as soon as practicable and preferably 

within one hour. If the repeat sample confirms that the maximum allowable limit has been exceeded, the 

supplier of water shall report to the State within 48 hours. The repeat sample shall be the sample used 

for the purpose of calculating the monthly average. If the monthly average of the daily samples exceeds 

the maximum allowable limit, or if the average of two samples taken on consecutive days exceeds 5 TU, 

the supplier of water shall report to the State and notify the public as directed in §141.31 and subpart Q. 

(c) Sampling for non-community water systems shall begin within two years after the effective date of 

this part. 

(d) The requirements of this §141.22 shall apply only to public water systems which use water obtained 

in whole or in part from surface sources. 

(e) The State has the authority to determine compliance or initiate enforcement action based upon 

analytical results or other information compiled by their sanctioned representatives and agencies. 

[40 FR 59570, Dec. 24, 1975, as amended at 45 FR 57344, Aug. 27, 1980; 47 FR 8998, Mar. 3, 1982; 

47 FR 10998, Mar. 12, 1982; 54 FR 27527, June 29, 1989; 59 FR 62466, Dec. 5, 1994; 65 FR 26022, 

May 4, 2000] 

§ 141.23 Inorganic chemical sampling and analytical requirements. 

 top

Community water systems shall conduct monitoring to determine compliance with the maximum 

contaminant levels specified in §141.62 in accordance with this section. Non-transient, non-community 

water systems shall conduct monitoring to determine compliance with the maximum contaminant levels 

specified in §141.62 in accordance with this section. Transient, non-community water systems shall 

conduct monitoring to determine compliance with the nitrate and nitrite maximum contaminant levels in 

§§141.11 and 141.62 (as appropriate) in accordance with this section. 

(a) Monitoring shall be conducted as follows: 

(1) Groundwater systems shall take a minimum of one sample at every entry point to the distribution 

system which is representative of each well after treatment (hereafter called a sampling point) beginning 

in the initial compliance period. The system shall take each sample at the same sampling point unless 

conditions make another sampling point more representative of each source or treatment plant. 

(2) Surface water systems shall take a minimum of one sample at every entry point to the distribution 

system after any application of treatment or in the distribution system at a point which is representative 

of each source after treatment (hereafter called a sampling point) beginning in the initial compliance 

period. The system shall take each sample at the same sampling point unless conditions make another 

sampling point more representative of each source or treatment plant. 

Note: For purposes of this paragraph, surface water systems include systems with a 

combination of surface and ground sources.

(3) If a system draws water from more than one source and the sources are combined before 

distribution, the system must sample at an entry point to the distribution system during periods of normal 

operating conditions ( i.e. , when water is representative of all sources being used). 

(4) The State may reduce the total number of samples which must be analyzed by allowing the use of 

compositing. Composite samples from a maximum of five samples are allowed, provided that the 

detection limit of the method used for analysis is less than one-fifth of the MCL. Compositing of samples 

must be done in the laboratory. 

(i) If the concentration in the composite sample is greater than or equal to one-fifth of the MCL of any 

inorganic chemical, then a follow-up sample must be taken within 14 days at each sampling point 

included in the composite. These samples must be analyzed for the contaminants which exceeded onefifth of the MCL in the composite sample. Detection limits for each analytical method and MCLs for each 

inorganic contaminant are the following: 

Detection Limits for Inorganic Contaminants 

MCL Detection limit 

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1MFL = million fibers per liter >10 μm.

Contaminant (mg/l) Methodology (mg/l)

Antimony 0.006 Atomic Absorption; Furnace 0.003

 Atomic Absorption; Platform 0.00085

 ICP-Mass Spectrometry 0.0004

 Hydride-Atomic Absorption 0.001

Arsenic 0.0106 Atomic Absorption; Furnace 0.001

 Atomic Absorption; Platform—

Stabilized Temperature

0.00057

 Atomic Absorption; Gaseous 

Hydride

0.001

 ICP-Mass Spectrometry 0.00148

Asbestos 7 MFL1 Transmission Electron Microscopy 0.01 MFL

Barium 2 Atomic Absorption; furnace 

technique

0.002

 Atomic Absorption; direct aspiration 0.1

 Inductively Coupled Plasma 0.002 (0.001)

Beryllium 0.004 Atomic Absorption; Furnace 0.0002

 Atomic Absorption; Platform 0.000025

 Inductively Coupled Plasma2 0.0003

 ICP-Mass Spectrometry 0.0003

Cadmium 0.005 Atomic Absorption; furnace 

technique

0.0001

 Inductively Coupled Plasma 0.001

Chromium 0.1 Atomic Absorption; furnace 

technique

0.001

 Inductively Coupled Plasma 0.007 (0.001)

Cyanide 0.2 Distillation, Spectrophotometric3 0.02

 Distillation, Automated, 

Spectrophotometric3

0.005

 Distillation, Amenable, 

Spectrophotometric4

0.02

 Distillation, Selective Electrode3, 4 0.05

 UV, Distillation, Spectrophotometric9 0.0005

 Micro Distillation, Flow Injection, 

Spectrophotometric3

0.0006

 Ligand Exchange with 

Amperometry4

0.0005

Mercury 0.002 Manual Cold Vapor Technique 0.0002

 Automated Cold Vapor Technique 0.0002

Nickel xl Atomic Absorption; Furnace 0.001

 Atomic Absorption; Platform 0.00065

 Inductively Coupled Plasma2 0.005

 ICP-Mass Spectrometry 0.0005

Nitrate 10 (as 

N)

Manual Cadmium Reduction 0.01

 Automated Hydrazine Reduction 0.01

 Automated Cadmium Reduction 0.05

 Ion Selective Electrode 1

 Ion Chromatography 0.01

 Capillary Ion Electrophoresis 0.076

Nitrite 1 (as N) Spectrophotometric 0.01

 Automated Cadmium Reduction 0.05

 Manual Cadmium Reduction 0.01

 Ion Chromatography 0.004

 Capillary Ion Electrophoresis 0.103

Selenium 0.05 Atomic Absorption; furnace 0.002

 Atomic Absorption; gaseous hydride 0.002

Thallium 0.002 Atomic Absorption; Furnace 0.001

 Atomic Absorption; Platform 0.00075

 ICP-Mass Spectrometry 0.0003

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2Using a 2X preconcentration step as noted in Method 200.7. Lower MDLs may be achieved when using 

a 4X preconcentration. 

3Screening method for total cyanides.

4Measures “free” cyanides when distillation, digestion, or ligand exchange is omitted.

5Lower MDLs are reported using stabilized temperature graphite furnace atomic absorption.

6The value for arsenic is effective January 23, 2006. Unit then, the MCL is 0.05 mg/L.

7The MDL reported for EPA method 200.9 (Atomic Absorption; Platform—Stablized Temperature) was 

determined using a 2x concentration step during sample digestion. The MDL determined for samples 

analyzed using direct analyses ( i.e. , no sample digestion) will be higher. Using multiple depositions, 

EPA 200.9 is capable of obtaining MDL of 0.0001 mg/L. 

8Using selective ion monitoring, EPA Method 200.8 (ICP-MS) is capable of obtaining a MDL of 0.0001 

mg/L. 

9Measures total cyanides when UV-digestor is used, and “free” cyanides when UV-digestor is bypassed.

(ii) If the population served by the system is >3,300 persons, then compositing may only be permitted by 

the State at sampling points within a single system. In systems serving ≤3,300 persons, the State may 

permit compositing among different systems provided the 5-sample limit is maintained. 

(iii) If duplicates of the original sample taken from each sampling point used in the composite sample are 

available, the system may use these instead of resampling. The duplicates must be analyzed and the 

results reported to the State within 14 days after completing analysis of the composite sample, provided 

the holding time of the sample is not exceeded. 

(5) The frequency of monitoring for asbestos shall be in accordance with paragraph (b) of this section: 

the frequency of monitoring for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, 

fluoride, mercury, nickel, selenium and thallium shall be in accordance with paragraph (c) of this section; 

the frequency of monitoring for nitrate shall be in accordance with paragraph (d) of this section; and the 

frequency of monitoring for nitrite shall be in accordance with paragraph (e) of this section. 

(b) The frequency of monitoring conducted to determine compliance with the maximum contaminant 

level for asbestos specified in §141.62(b) shall be conducted as follows: 

(1) Each community and non-transient, non-community water system is required to monitor for asbestos 

during the first three-year compliance period of each nine-year compliance cycle beginning in the 

compliance period starting January 1, 1993. 

(2) If the system believes it is not vulnerable to either asbestos contamination in its source water or due 

to corrosion of asbestos-cement pipe, or both, it may apply to the State for a waiver of the monitoring 

requirement in paragraph (b)(1) of this section. If the State grants the waiver, the system is not required 

to monitor. 

(3) The State may grant a waiver based on a consideration of the following factors: 

(i) Potential asbestos contamination of the water source, and 

(ii) The use of asbestos-cement pipe for finished water distribution and the corrosive nature of the water. 

(4) A waiver remains in effect until the completion of the three-year compliance period. Systems not 

receiving a waiver must monitor in accordance with the provisions of paragraph (b)(1) of this section. 

(5) A system vulnerable to asbestos contamination due solely to corrosion of asbestos-cement pipe shall 

take one sample at a tap served by asbestos-cement pipe and under conditions where asbestos 

contamination is most likely to occur. 

(6) A system vulnerable to asbestos contamination due solely to source water shall monitor in 

accordance with the provision of paragraph (a) of this section. 

(7) A system vulnerable to asbestos contamination due both to its source water supply and corrosion of 

asbestos-cement pipe shall take one sample at a tap served by asbestos-cement pipe and under 

conditions where asbestos contamination is most likely to occur. 

(8) A system which exceeds the maximum contaminant levels as determined in §141.23(i) of this section 

shall monitor quarterly beginning in the next quarter after the violation occurred. 

(9) The State may decrease the quarterly monitoring requirement to the frequency specified in 

paragraph (b)(1) of this section provided the State has determined that the system is reliably and 

consistently below the maximum contaminant level. In no case can a State make this determination 

unless a groundwater system takes a minimum of two quarterly samples and a surface (or combined 

surface/ground) water system takes a minimum of four quarterly samples. 

(10) If monitoring data collected after January 1, 1990 are generally consistent with the requirements of 

§141.23(b), then the State may allow systems to use that data to satisfy the monitoring requirement for 

the initial compliance period beginning January 1, 1993. 

(c) The frequency of monitoring conducted to determine compliance with the maximum contaminant 

levels in §141.62 for antimony, arsenic, barium, beryllium, cadmium, chromium, cyanide, fluoride, 

mercury, nickel, selenium and thallium shall be as follows: 

(1) Groundwater systems shall take one sample at each sampling point during each compliance period. 

Surface water systems (or combined surface/ground) shall take one sample annually at each sampling 

point. 

(2) The system may apply to the State for a waiver from the monitoring frequencies specified in 

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paragraph (c)(1) of this section. States may grant a public water system a waiver for monitoring of 

cyanide, provided that the State determines that the system is not vulnerable due to lack of any 

industrial source of cyanide. 

(3) A condition of the waiver shall require that a system shall take a minimum of one sample while the 

waiver is effective. The term during which the waiver is effective shall not exceed one compliance cycle 

( i.e. , nine years). 

(4) The State may grant a waiver provided surface water systems have monitored annually for at least 

three years and groundwater systems have conducted a minimum of three rounds of monitoring. (At 

least one sample shall have been taken since January 1, 1990). Both surface and groundwater systems 

shall demonstrate that all previous analytical results were less than the maximum contaminant level. 

Systems that use a new water source are not eligible for a waiver until three rounds of monitoring from 

the new source have been completed. 

(5) In determining the appropriate reduced monitoring frequency, the State shall consider: 

(i) Reported concentrations from all previous monitoring; 

(ii) The degree of variation in reported concentrations; and 

(iii) Other factors which may affect contaminant concentrations such as changes in groundwater 

pumping rates, changes in the system's configuration, changes in the system's operating procedures, or 

changes in stream flows or characteristics. 

(6) A decision by the State to grant a waiver shall be made in writing and shall set forth the basis for the 

determination. The determination may be initiated by the State or upon an application by the public 

water system. The public water system shall specify the basis for its request. The State shall review and, 

where appropriate, revise its determination of the appropriate monitoring frequency when the system 

submits new monitoring data or when other data relevant to the system's appropriate monitoring 

frequency become available. 

(7) Systems which exceed the maximum contaminant levels as calculated in §141.23(i) of this section 

shall monitor quarterly beginning in the next quarter after the violation occurred. 

(8) The State may decrease the quarterly monitoring requirement to the frequencies specified in 

paragraphs (c)(1) and (c)(2) of this section provided it has determined that the system is reliably and 

consistently below the maximum contaminant level. In no case can a State make this determination 

unless a groundwater system takes a minimum of two quarterly samples and a surface water system 

takes a minimum of four quarterly samples. 

(9) All new systems or systems that use a new source of water that begin operation after January 22, 

2004 must demonstrate compliance with the MCL within a period of time specified by the State. The 

system must also comply with the initial sampling frequencies specified by the State to ensure a system 

can demonstrate compliance with the MCL. Routine and increased monitoring frequencies shall be 

conducted in accordance with the requirements in this section. 

(d) All public water systems (community; non-transient, non-community; and transient, non-community 

systems) shall monitor to determine compliance with the maximum contaminant level for nitrate in 

§141.62. 

(1) Community and non-transient, non-community water systems served by groundwater systems shall 

monitor annually beginning January 1, 1993; systems served by surface water shall monitor quarterly 

beginning January 1, 1993. 

(2) For community and non-transient, non-community water systems, the repeat monitoring frequency 

for groundwater systems shall be quarterly for at least one year following any one sample in which the 

concentration is ≥50 percent of the MCL. The State may allow a groundwater system to reduce the 

sampling frequency to annually after four consecutive quarterly samples are reliably and consistently 

less than the MCL. 

(3) For community and non-transient, non-community water systems, the State may allow a surface 

water system to reduce the sampling frequency to annually if all analytical results from four consecutive 

quarters are <50 percent of the MCL. A surface water system shall return to quarterly monitoring if any 

one sample is ≥50 percent of the MCL. 

(4) Each transient non-community water system shall monitor annually beginning January 1, 1993. 

(5) After the initial round of quarterly sampling is completed, each community and non-transient noncommunity system which is monitoring annually shall take subsequent samples during the quarter(s) 

which previously resulted in the highest analytical result. 

(e) All public water systems (community; non-transient, non-community; and transient, non-community 

systems) shall monitor to determine compliance with the maximum contaminant level for nitrite in 

§141.62(b). 

(1) All public water systems shall take one sample at each sampling point in the compliance period 

beginning January 1, 1993 and ending December 31, 1995. 

(2) After the initial sample, systems where an analytical result for nitrite is <50 percent of the MCL shall 

monitor at the frequency specified by the State. 

(3) For community, non-transient, non-community, and transient non-community water systems, the 

repeat monitoring frequency for any water system shall be quarterly for at least one year following any 

one sample in which the concentration is ≥50 percent of the MCL. The State may allow a system to 

reduce the sampling frequency to annually after determining the system is reliably and consistently less 

than the MCL. 

(4) Systems which are monitoring annually shall take each subsequent sample during the quarter(s) 

which previously resulted in the highest analytical result. 

(f) Confirmation samples: 

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(1) Where the results of sampling for antimony, arsenic, asbestos, barium, beryllium, cadmium, 

chromium, cyanide, fluoride, mercury, nickel, selenium or thallium indicate an exceedance of the 

maximum contaminant level, the State may require that one additional sample be collected as soon as 

possible after the initial sample was taken (but not to exceed two weeks) at the same sampling point. 

(2) Where nitrate or nitrite sampling results indicate an exceedance of the maximum contaminant level, 

the system shall take a confirmation sample within 24 hours of the system's receipt of notification of the 

analytical results of the first sample. Systems unable to comply with the 24-hour sampling requirement 

must immediately notify persons served by the public water system in accordance with §141.202 and 

meet other Tier 1 public notification requirements under Subpart Q of this part. Systems exercising this 

option must take and analyze a confirmation sample within two weeks of notification of the analytical 

results of the first sample. 

(3) If a State-required confirmation sample is taken for any contaminant, then the results of the initial and 

confirmation sample shall be averaged. The resulting average shall be used to determine the system's 

compliance in accordance with paragraph (i) of this section. States have the discretion to delete results 

of obvious sampling errors. 

(g) The State may require more frequent monitoring than specified in paragraphs (b), (c), (d) and (e) of 

this section or may require confirmation samples for positive and negative results at its discretion. 

(h) Systems may apply to the State to conduct more frequent monitoring than the minimum monitoring 

frequencies specified in this section. 

(i) Compliance with §§141.11 or 141.62(b) (as appropriate) shall be determined based on the analytical 

result(s) obtained at each sampling point. 

(1) For systems which are conducting monitoring at a frequency greater than annual, compliance with 

the maximum contaminant levels for antimony, arsenic, asbestos, barium, beryllium, cadmium, 

chromium, cyanide, fluoride, mercury, nickel, selenium or thallium is determined by a running annual 

average at any sampling point. If the average at any sampling point is greater than the MCL, then the 

system is out of compliance. If any one sample would cause the annual average to be exceeded, then 

the system is out of compliance immediately. Any sample below the method detection limit shall be 

calculated at zero for the purpose of determining the annual average. If a system fails to collect the 

required number of samples, compliance (average concentration) will be based on the total number of 

samples collected. 

(2) For systems which are monitoring annually, or less frequently, the system is out of compliance with 

the maximum contaminant levels for antimony, arsenic, asbestos, barium, beryllium, cadmium, 

chromium, cyanide, fluoride, mercury, nickel, selenium or thallium if the level of a contaminant is greater 

than the MCL. If confirmation samples are required by the State, the determination of compliance will be 

based on the annual average of the initial MCL exceedance and any State-required confirmation 

samples. If a system fails to collect the required number of samples, compliance (average concentration) 

will be based on the total number of samples collected. 

(3) Compliance with the maximum contaminant levels for nitrate and nitrate is determined based on one 

sample if the levels of these contaminants are below the MCLs. If the levels of nitrate and/or nitrite 

exceed the MCLs in the initial sample, a confirmation sample is required in accordance with paragraph 

(f)(2) of this section, and compliance shall be determined based on the average of the initial and 

confirmation samples. 

(4) Arsenic sampling results will be reported to the nearest 0.001 mg/L. 

(j) Each public water system shall monitor at the time designated by the State during each compliance 

period. 

(k) Inorganic analysis: 

(1) Analysis for the following contaminants shall be conducted in accordance with the methods in the 

following table, or the alternative methods listed in appendix A to subpart C of this part, or their 

equivalent as determined by EPA. Criteria for analyzing arsenic, barium, beryllium, cadmium, calcium, 

chromium, copper, lead, nickel, selenium, sodium, and thallium with digestion or directly without 

digestion, and other analytical test procedures are contained in Technical Notes on Drinking Water 

Methods, EPA–600/R–94–173, October 1994. This document is available from the National Service 

Center for Environmental Publications (NSCEP), P.O. Box 42419, Cincinnati, OH 45242–0419 or 

http://www.epa.gov/nscep/ . 

Contaminant Methodology13 EPA ASTM3

SM4

(18th, 

19th 

ed.)

SM4

(20th 

ed.)

SM 

Online22 Other

1. Alkalinity Titrimetric D1067–92, 

02 B

2320 B 2320 B 2320 B–

97

 Electrometric 

titration

I–1030–

855

2. Antimony Inductively Coupled 

Plasma (ICP)—

Mass Spectrometry

200.82

 Hydride-Atomic 

Absorption

D3697–92, 

02

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Furnace

3113 B 3113 B–

99

3. Arsenic14 ICP-Mass 

Spectrometry

200.82

 Atomic Absorption; 200.92

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Platform

 Atomic Absorption; 

Furnace

D2972–97, 

03 C

3113 B 3113 B–

99

 Hydride Atomic 

Absorption

D1972–97, 

03 B

3114 B 3114 B–

97

4. Asbestos Transmission 

Electron 

Microscopy

100.19

 Transmission 

Electron 

Microscopy

100.210

5. Barium Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 ICP-Mass 

Spectrometry

200.82

 Atomic Absorption; 

Direct

3111D 3111 D–

99

 Atomic Absorption; 

Furnace

3113 B 3113 B–

99

6. Beryllium Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 ICP-Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Furnace

D3645–97, 

03 B

3113 B 3113 B–

99

7. Cadmium Inductively Coupled 

Plasma

200.72

 ICP-Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Furnace

3113 B 3113 B–

99

8. Calcium EDTA titrimetric D511–93, 03 

A

3500–

Ca D

3500–

Ca B

3500–

Ca B–97

 Atomic Absorption; 

Direct Aspiration

D511–93, 03 

B

3111 B 3111 B–

99

 Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 Ion 

Chromatography

D6919–03

9. Chromium Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 ICP-Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Furnace

3113 B 3113 B–

99

10. Copper Atomic Absorption; 

Furnace

D1688–95, 

02 C

3113 B 3113 B–

99

 Atomic Absorption; 

Direct Aspiration

D1688–95, 

02 A

3111 B 3111 B–

99

 Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 ICP-Mass 

spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

11. 

Conductivity

Conductance D1125–95 

(Reapproved 

1999) A

2510 B 2510 B 2510 B–

97

12. Cyanide Manual Distillation 

followed by

D2036–98 A 4500–

CN−C

4500–

CN−C

 Spectrophotometric, 

Amenable

D2036–98 B 4500–

CN−G

4500–

CN−G

4500–

CN−G–

99

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 Spectrophotometric Manual

D2036–98 A 4500–

CN−E

4500–

CN−E

4500–

CN−E–

99

I–3300–

855

 Spectrophotometric Semiautomated

335.46

 Selective Electrode 4500–

CN−F

4500–

CN−F

4500–

CN−F–

99

 UV, Distillation, 

Spectrophotometric

Kelada–

0117

 Micro Distillation, 

Flow Injection, 

Spectrophotometric

QuikChem 

10–204–

00–1–X18

 Ligand Exchange 

and Amperometry21

D6888–04 OIA–

1677, 

DW20

13. Fluoride Ion 

Chromatography

300.06, 

300.119

D4327–97, 

03

4110 B 4110 B 4110 B–

00

 Manual Distill.; 

Color. SPADNS

4500–

F−B, D

4500–

F−B, D

4500–

F−B, D–

97

 Manual Electrode D1179–93, 

99 B

4500–

F−C

4500–

F−C

4500–

F−C–97

 Automated 

Electrode

380–

75WE11

 Automated Alizarin 4500–

F−E

4500–

F−E

4500–

F−E–97

129–

71W11

 Capillary Ion 

Electrophoresis

D6508, 

Rev. 223

14. Lead Atomic Absorption; 

Furnace

D3559–96, 

03 D

3113 B 3113 B–

99

 ICP–Mass 

spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Differential Pulse 

Anodic Stripping 

Voltametry

Method 

100116

15. 

Magnesium

Atomic Absorption D511–93, 03 

B

3111 B 3111 B–

99

 ICP 200.72 3120 B 3120 B 3120 B–

99

 Complexation 

Titrimetric Methods

D511–93, 03 

A

3500–

Mg E

3500–

Mg B

3500–

Mg B–97

 Ion 

Chromatography

D6919–03

16. Mercury Manual, Cold Vapor 245.12 D3223–97, 

02

3112 B 3112 B–

99

 Automated, Cold 

Vapor

245.21

 ICP–Mass 

Spectrometry

200.82

17. Nickel Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

 ICP–Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Direct

3111 B 3111 B–

99

 Atomic Absorption; 

Furnace

3113 B 3113 B–

99

18. Nitrate Ion 

Chromatography

300.06300.119 D4327–97, 

03

4110 B 4110 B 4110 B–

00

B–10118

 Automated 

Cadmium 

Reduction

353.26 D3867–90 A 4500–

NO3−F

4500–

NO3−F

4500–

NO3−F–

00

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 Ion Selective 

Electrode

4500–

NO3−D

4500–

NO3−D

4500–

NO3−D–

00

6017

 Manual Cadmium 

Reduction

D3867–90 B 4500–

NO3−E

4500–

NO3−E

4500–

NO3−E–

00

 Capillary Ion 

Electrophoresis

D6508, 

Rev. 223

19. Nitrite Ion 

Chromatography

300.06300.119 D4327–97, 

03

4110 B 4110 B 4110 B–

00

B–10118

 Automated 

Cadmium 

Reduction

353.26 D3867–90 A 4500–

NO3−F

4500–

NO3−F

4500–

NO3−F–

00

 Manual Cadmium 

Reduction

D3867–90 B 4500–

NO3−E

4500–

NO3−E

4500–

NO3−E–

00

 Spectrophotometric 4500–

NO2−B

4500–

NO2−B

4500–

NO2−B–

00

 Capillary Ion 

Electrophoresis

D6508, 

Rev. 223

20. Orthophosphate12Colorimetric, 

Automated, 

Ascorbic Acid

365.16 4500–

P F

4500–

P F

 Colorimetric, 

ascorbic acid, 

single reagent

D515–88 A 4500–

P E

4500–

P E

 Colorimetric 

Phosphomolybdate;

I–1601–

855

 Automatedsegmented flow;I–2601–

905

 Automated Discrete I–2598–

855

 Ion 

Chromatography

300.06

300.119

D4327–97, 

03

4110 B 4110 B 4110 B–

00

 Capillary Ion 

Electrophoresis

D6508, 

Rev. 223

21. pH Electrometric 150.1, 150.21 D1293–95, 

99

4500–

H+B

4500–

H+B

4500–

H+B–00

22. Selenium Hydride-Atomic 

Absorption

D3859–98, 

03 A

3114 B 3114 B–

97

ICP–Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

 Atomic Absorption; 

Furnace

D3859–98, 

03 B

3113 B 3113 B–

99

23. Silica Colorimetric, 

Molybdate Blue

I–1700–

855

 Automatedsegmented FlowI–2700–

855

 Colorimetric D859–94, 00

 Molybdosilicate 4500–

Si D

4500–

SiO2 C

4500–

SiO2 C–

97

 Heteropoly blue 4500–

Si E

4500–

SiO2 D

4500–

SiO2 D–

97

 Automated for 

Molybdate-reactive 

Silica

4500–

Si F

4500–

SiO2 E

4500–

SiO2 E–

97

 Inductively Coupled 

Plasma

200.72 3120 B 3120 B 3120 B–

99

24. Sodium Inductively Coupled 

Plasma

200.72

 Atomic Absorption; 

Direct Aspiration

3111 B 3111 B–

99

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The procedures shall be done in accordance with the documents listed below. The incorporation by 

reference of the following documents listed in footnotes 1–11, 16–20, and 22–23 was approved by the 

Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the 

documents may be obtained from the sources listed below. Information regarding obtaining these 

documents can be obtained from the Safe Drinking Water Hotline at 800–426–4791. Documents may be 

inspected at EPA's Drinking Water Docket, EPA West, 1301 Constitution Avenue, NW., Room 3334, 

Washington, DC 20460 (Telephone: 202–566–2426); or at the National Archives and Records 

Administration (NARA). For information on the availability of this material at NARA, call 202–741–6030, 

or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html . 

1“Methods for Chemical Analysis of Water and Wastes,” EPA/600/4–79/020, March 1983. Available at 

NTIS, PB84–128677. 

2“Methods for the Determination of Metals in Environmental Samples—Supplement I,” EPA/600/R–

94/111, May 1994. Available at NTIS, PB95–125472. 

3 Annual Book of ASTM Standards, 1994, 1996, 1999, or 2003, Vols. 11.01 and 11.02, ASTM 

International; any year containing the cited version of the method may be used. The previous versions of 

D1688–95A, D1688–95C (copper), D3559–95D (lead), D1293–95 (pH), D1125–91A (conductivity) and 

D859–94 (silica) are also approved. These previous versions D1688–90A, C; D3559–90D, D1293–84, 

D1125–91A and D859–88, respectively are located in the Annual Book of ASTM Standards, 1994, Vol. 

11.01. Copies may be obtained from ASTM International, 100 Barr Harbor Drive, West Conshohocken, 

PA 19428. 

4 Standard Methods for the Examination of Water and Wastewater, 18th edition (1992), 19th edition 

(1995), or 20th edition (1998). American Public Health Association, 1015 Fifteenth Street, NW., 

Washington, DC 20005. The cited methods published in any of these three editions may be used, except 

that the versions of 3111 B, 3111 D, 3113 B and 3114 B in the 20th edition may not be used. 

5Method I–2601–90, Methods for Analysis by the U.S. Geological Survey National Water Quality 

Laboratory—Determination of Inorganic and Organic Constituents in Water and Fluvial Sediment, Open 

File Report 93–125, 1993; For Methods I–1030–85; I–1601–85; I–1700–85; I–2598–85; I–2700–85; and 

I–3300–85 See Techniques of Water Resources Investigation of the U.S. Geological Survey, Book 5, 

Chapter A–1, 3rd edition., 1989; Available from Information Services, U.S. Geological Survey, Federal 

Center, Box 25286, Denver, CO 80225–0425. 

6“Methods for the Determination of Inorganic Substances in Environmental Samples,” EPA/600/R–

93/100, August 1993. Available at NTIS, PB94–120821. 

7The procedure shall be done in accordance with the Technical Bulletin 601 ” Standard Method of Test 

for Nitrate in Drinking Water,” July 1994, PN 221890–001, Analytical Technology, Inc. Copies may be 

obtained from ATI Orion, 529 Main Street, Boston, MA 02129. 

8Method B–1011, “Waters Test Method for Determination of Nitrite/Nitrate in Water Using Single Column 

Ion Chromatography,” August 1987. Copies may be obtained from Waters Corporation, Technical 

Services Division, 34 Maple Street, Milford, MA 01757, Telephone: 508/482–2131, Fax: 508/482–3625. 

9Method 100.1, “Analytical Method For Determination of Asbestos Fibers in Water,” EPA/600/4–83/043, 

EPA, September 1983. Available at NTIS, PB83–260471. 

10Method 100.2, “Determination of Asbestos Structure Over 10-μm In Length In Drinking Water,” 

EPA/600/R–94/134, June 1994. Available at NTIS, PB94–201902. 

11Industrial Method No. 129–71W, “Fluoride in Water and Wastewater,” December 1972, and Method 

No. 380–75WE, “Fluoride in Water and Wastewater,” February 1976, Technicon Industrial Systems. 

Copies may be obtained from Bran & Luebbe, 1025 Busch Parkway, Buffalo Grove, IL 60089. 

12Unfiltered, no digestion or hydrolysis.

13Because MDLs reported in EPA Methods 200.7 and 200.9 were determined using a 2x 

preconcentration step during sample digestion, MDLs determined when samples are analyzed by direct 

analysis ( i.e. , no sample digestion) will be higher. For direct analysis of cadmium by Method 200.7, 

sample preconcentration using pneumatic nebulization may be required to achieve lower detection 

limits. Preconcentration may also be required for direct analysis of antimony, lead, and thallium by 

Method 200.9; antimony and lead by Method 3113 B; and lead by Method D3559–90D, unless multiple 

in-furnace depositions are made. 

14If ultrasonic nebulization is used in the determination of arsenic by Method 200.8, the arsenic must be 

in the pentavalent state to provide uniform signal response. For direct analysis of arsenic with Method 

200.8 using ultrasonic nebulization, samples and standards must contain 1 mg/L of sodium hypochlorite. 

15[Reserved]

16The description for Method Number 1001 for lead is available from Palintest, LTD, 21 Kenton Lands 

Road, P.O. Box 18395, Erlanger, KY 41018. Or from the Hach Company, P.O. Box 389, Loveland, CO 

80539. 

17The description for the Kelada-01 Method, “Kelada Automated Test Methods for Total Cyanide, Acid 

Dissociable Cyanide, And Thiocyanate,” Revision 1.2, August 2001, EPA # 821–B–01–009 for cyanide 

 Ion 

Chromatography

D6919–03

25. 

Temperature

Thermometric 2550 2550 2550–00

26. Thallium ICP–Mass 

Spectrometry

200.82

 Atomic Absorption; 

Platform

200.92

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is available from the National Technical Information Service (NTIS), PB 2001–108275, 5285 Port Royal 

Road, Springfield, VA 22161. The toll free telephone number is 800–553–6847.Note:A 450–W UV lamp 

may be used in this method instead of the 550–W lamp specified if it provides performance within the 

quality control (QC) acceptance criteria of the method in a given instrument. Similarly, modified flow cell 

configurations and flow conditions may be used in the method, provided that the QC acceptance criteria 

are met. 

18The description for the QuikChem Method 10–204–00–1–X, “Digestion and distillation of total cyanide 

in drinking and wastewaters using MICRO DIST and determination of cyanide by flow injection analysis,” 

Revision 2.1, November 30, 2000, for cyanide is available from Lachat Instruments, 6645 W. Mill Rd., 

Milwaukee, WI 53218. Telephone: 414–358–4200. 

19“Methods for the Determination of Organic and Inorganic Compounds in Drinking Water,” Vol. 1, EPA 

815–R–00–014, August 2000. Available at NTIS, PB2000–106981. 

20Method OIA–1677, DW “Available Cyanide by Flow Injection, Ligand Exchange, and Amperometry,” 

January 2004. EPA–821–R–04–001, Available from ALPKEM, A Division of OI Analytical, P.O. Box 

9010, College Station, TX 77842–9010. 

21Sulfide levels below those detected using lead acetate paper may produce positive method 

interferences. Test samples using a more sensitive sulfide method to determine if a sulfide interference 

is present, and treat samples accordingly. 

22Standard Methods Online are available at http://www.standardmethods.org . The year in which each 

method was approved by the Standard Methods Committee is designated by the last two digits in the 

method number. The methods listed are the only online versions that may be used. 

23Method D6508, Rev. 2, “Test Method for Determination of Dissolved Inorganic Anions in Aqueous 

Matrices Using Capillary Ion Electrophoresis and Chromate Electrolyte,” available from Waters Corp, 34 

Maple St, Milford, MA, 01757, Telephone: 508/482–2131, Fax: 508/482–3625. 

(2) Sample collection for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, cyanide, 

fluoride, mercury, nickel, nitrate, nitrite, selenium, and thallium under this section shall be conducted 

using the sample preservation, container, and maximum holding time procedures specified in the table 

below: 

1For cyanide determinations samples must be adjusted with sodium hydroxide to pH 12 at the time off 

collection. When chilling is indicated the sample must be shipped and stored at 4 °C or less. Acidification 

of nitrate or metals samples may be with a concentrated acid or a dilute (50% by volume) solution of the 

applicable concentrated acid. Acidification of samples for metals analysis is encouraged and allowed at 

the laboratory rather than at the time of sampling provided the shipping time and other instructions in 

Section 8.3 of EPA Methods 200.7 or 200.8 or 200.9 are followed. 

2P=plastic, hard or soft; G=glass, hard or soft.

3In all cases samples should be analyzed as soon after collection as possible. Follow additional (if any) 

information on preservation, containers or holding times that is specified in method. 

4Instructions for containers, preservation procedures and holding times as specified in Method 100.2 

must be adhered to for all compliance analyses including those conducted with Method 100.1. 

5If the sample is chlorinated, the holding time for an unacidified sample kept at 4 °C is extended to 14 

days. 

6Nitrate-Nitrite refers to a measurement of total nitrate.

(3) Analysis under this section shall only be conducted by laboratories that have been certified by EPA 

or the State. Laboratories may conduct sample analysis under provisional certification until January 1, 

1996. To receive certification to conduct analyses for antimony, arsenic, asbestos, barium, beryllium, 

cadmium, chromium, cyanide, fluoride, mercury, nickel, nitrate, nitrite and selenium and thallium, the 

laboratory must: 

Contaminant Preservative1 Container2 Time3

Antimony HNO3 P or G 6 months

Arsenic Conc HNO3to pH <2 P or G 6 months

Asbestos 4 °C P or G 48 hours4

Barium HNO3 P or G 6 months

Beryllium HNO3 P or G 6 months

Cadmium HNO3 P or G 6 months

Chromium HNO3 P or G 6 months

Cyanide 4 °C, NaOH P or G 14 days

Fluoride None P or G 1 month

Mercury HNO3 P or G 28 days

Nickel HNO3 P or G 6 months

Nitrate 4 °C P or G 48 hours5

Nitrate-Nitrite6 H2SO4 P or G 28 days

Nitrite 4°C P or G 48 hours

Selenium HNO3 P or G 6 months

Thallium HNO3 P or G 6 months

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(i) Analyze Performance Evaluation (PE) samples provided by EPA, the State or by a third party (with 

the approval of the State or EPA) at least once a year. 

(ii) For each contaminant that has been included in the PE sample and for each method for which the 

laboratory desires certification achieve quantitative results on the analyses that are within the following 

acceptance limits: 

(l) Analyses for the purpose of determining compliance with §141.11 shall be conducted using the 

requirements specified in paragraphs (l) through (q) of this section. 

(1) Analyses for all community water systems utilizing surface water sources shall be completed by June 

24, 1978. These analyses shall be repeated at yearly intervals. 

(2) Analyses for all community water systems utilizing only ground water sources shall be completed by 

June 24, 1979. These analyses shall be repeated at three-year intervals. 

(3) For non-community water systems, whether supplied by surface or ground sources, analyses for 

nitrate shall be completed by December 24, 1980. These analyses shall be repeated at intervals 

determined by the State. 

(4) The State has the authority to determine compliance or initiate enforcement action based upon 

analytical results and other information compiled by their sanctioned representatives and agencies. 

(m) If the result of an analysis made under paragraph (l) of this section indicates that the level of any 

contaminant listed in §141.11 exceeds the maximum contaminant level, the supplier of the water shall 

report to the State within 7 days and initiate three additional analyses at the same sampling point within 

one month. 

(n) When the average of four analyses made pursuant to paragraph (m) of this section, rounded to the 

same number of significant figures as the maximum contaminant level for the substance in question, 

exceeds the maximum contaminant level, the supplier of water shall notify the State pursuant to §141.31 

and give notice to the public pursuant to subpart Q. Monitoring after public notification shall be at a 

frequency designated by the State and shall continue until the maximum contaminant level has not been 

exceeded in two successive samples or until a monitoring schedule as a condition to a variance, 

exemption or enforcement action shall become effective. 

(o) The provisions of paragraphs (m) and (n) of this section notwithstanding, compliance with the 

maximum contaminant level for nitrate shall be determined on the basis of the mean of two analyses. 

When a level exceeding the maximum contaminant level for nitrate is found, a second analysis shall be 

initiated within 24 hours, and if the mean of the two analyses exceeds the maximum contaminant level, 

the supplier of water shall report his findings to the State pursuant to §141.31 and shall notify the public 

pursuant to subpart Q. 

(p) For the initial analyses required by paragraph (l) (1), (2) or (3) of this section, data for surface waters 

acquired within one year prior to the effective date and data for ground waters acquired within 3 years 

prior to the effective date of this part may be substituted at the discretion of the State. 

(q) [Reserved] 

[56 FR 3579, Jan. 30, 1991] 

Editorial Note: For Federal Register citations affecting §141.23, see the List of CFR Sections 

Affected, which appears in the Finding Aids section of the printed volume and at www.fdsys.gov. 

§ 141.24 Organic chemicals, sampling and analytical requirements. 

 top

(a)–(d) [Reserved] 

(e) Analyses for the contaminants in this section shall be conducted using the methods listed in the 

following table, or the alternative methods listed in appendix A to subpart C of this part, or their 

equivalent as determined by EPA. 

(1) The following documents are incorporated by reference. This incorporation by reference was 

approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. 

Copies may be inspected at EPA's Drinking Water Docket, 1301 Constitution Avenue, NW., EPA West, 

Contaminant Acceptance limit

Antimony ±30 at ≥0.006 mg/1

Arsenic ±30 at ≥0.003 mg/L

Asbestos 2 standard deviations based on study statistics.

Barium ±15% at ≥0.15 mg/1

Beryllium ±15% at ≥0.001 mg/1

Cadmium ±20% at ≥0.002 mg/1

Chromium ±15% at ≥0.01 mg/1

Cyanide ±25% at ≥0.1 mg/1

Fluoride ±10% at ≥1 to 10 mg/1

Mercury ±30% at ≥0.0005 mg/1

Nickel ±15% at ≥0.01 mg/1

Nitrate ±10% at ≥0.4 mg/1

Nitrite ±15% at ≥0.4 mg/1

Selenium ±20% at ≥0.01 mg/1

Thallium ±30% at ≥0.002 mg/1

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Room 3334, Washington, DC 20460 (Telephone: 202–566–2426); or at the National Archives and 

Records Administration (NARA). For information on the availability of this material at NARA, call 202–

741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Method 508A 

and 515.1 are in Methods for the Determination of Organic Compounds in Drinking Water, EPA/600/4–

88–039, December 1988, Revised, July 1991. Methods 547, 550 and 550.1 are in Methods for the 

Determination of Organic Compounds in Drinking Water—Supplement I, EPA/600–4–90–020, July 1990. 

Methods 548.1, 549.1, 552.1 and 555 are in Methods for the Determination of Organic Compounds in 

Drinking Water—Supplement II, EPA/600/R–92–129, August 1992. Methods 502.2, 504.1, 505, 506, 

507, 508, 508.1, 515.2, 524.2 525.2, 531.1, 551.1 and 552.2 are in Methods for the Determination of 

Organic Compounds in Drinking Water––Supplement III, EPA/600/R–95–131, August 1995. Method 

1613 is titled “Tetra-through Octa-Chlorinated Dioxins and Furans by Isotope-Dilution HRGC/HRMS,” 

EPA/821–B–94–005, October 1994. These documents are available from the National Technical 

Information Service, NTIS PB91–231480, PB91–146027, PB92–207703, PB95–261616 and PB95–

104774, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia 22161. The toll free 

number is: 800–553–6847. Method 6651 shall be followed in accordance with Standard Methods for the 

Examination of Water and Wastewater, 18th edition (1992), 19th edition (1995), or 20th edition (1998), 

American Public Health Association (APHA); any of these three editions may be used. Method 6610 

shall be followed in accordance with Standard Methods for the Examination of Water and Wastewater, 

(18th Edition Supplement) (1994), or with the 19th edition (1995) or 20th edition (1998) of Standard 

Methods for the Examination of Water and Wastewater; any of these publications may be used. The 

APHA documents are available from APHA, 1015 Fifteenth Street NW., Washington, DC 20005. Other 

required analytical test procedures germane to the conduct of these analyses are contained in Technical 

Notes on Drinking Water Methods, EPA/600/R–94–173, October 1994, NTIS PB95–104766. EPA 

Methods 515.3 and 549.2 are available from U.S. Environmental Protection Agency, National Exposure 

Research Laboratory (NERL)–Cincinnati, 26 West Martin Luther King Drive, Cincinnati, OH 45268. 

ASTM Method D 5317–93, 98 (Reapproved 2003) is available in the Annual Book of ASTM Standards, 

(1999), Vol. 11.02, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428, any 

edition containing the cited version of the method may be used. EPA Method 515.4, “Determination of 

Chlorinated Acids in Drinking Water by Liquid-Liquid Microextraction, Derivatization and Fast Gas 

Chromatography with Electron Capture Detection,” Revision 1.0, April 2000, EPA/815/B–00/001 and 

EPA Method 552.3, “Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid 

Microextraction, Derivatization, and Gas Chromatography with Electron Capture Detection,” Revision 

1.0, July 2003, EPA 815–B–03–002, can be accessed and downloaded directly online at 

http://www.epa.gov/safewater/methods/sourcalt.html. Syngenta Method AG–625, “Atrazine in Drinking 

Water by Immunoassay,” February 2001, is available from Syngenta Crop Protection, Inc., 410 Swing 

Road, P.O. Box 18300, Greensboro, NC 27419. Telephone: 336–632–6000. Method 531.2 

“Measurement of N-methylcarbamoyloximes and N-methylcarbamates in Water by Direct Aqueous 

Injection HPLC with Postcolumn Derivatization,” Revision 1.0, September 2001, EPA 815–B–01–002, 

can be accessed and downloaded directly online at 

http://www.epa.gov/safewater/methods/sourcalt.html. 

Contaminant

EPA 

method

Standard 

methods ASTM Other

1. Benzene 502.2, 

524.2

2. Carbon tetrachloride 502.2, 

524.2, 

551.1

3. Chlorobenzene 502.2, 

524.2

4. 1,2-Dichlorobenzene 502.2, 

524.2

5. 1,4-Dichlorobenzene 502.2, 

524.2

6. 1,2-Dichloroethane 502.2, 

524.2

7. cis-Dichloroethylene 502.2, 

524.2

8. trans-Dichloroethylene 502.2, 

524.2

9. Dichloromethane 502.2, 

524.2

10. 1,2-Dichloropropane 502.2, 

524.2

11. Ethylbenzene 502.2, 

524.2

12. Styrene 502.2, 

524.2

13. Tetrachloroethylene 502.2, 

524.2, 

551.1

14. 1,1,1-Trichloroethane 502.2, 

524.2, 

551.1

15. Trichloroethylene 502.2, 

524.2, 

551.1

16. Toluene 502.2, 

524.2

17. 1,2,4-Trichlorobenzene 502.2, 

524.2

18. 1,1-Dichloroethylene 502.2, 

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524.2

19. 1,1,2-Trichloroethane 502.2, 

524.2, 

551.1

20. Vinyl chloride 502.2, 

524.2

21. Xylenes (total) 502.2, 

524.2

22. 2,3,7,8-TCDD (dioxin) 1613

23. 2,4–D4(as acids, salts, 

and esters)

515.2, 

555, 

515.1, 

515.3, 

515.4

D5317–93, 

98 

(Reapproved 

2003)

24. 2,4,5–TP4(Silvex) 515.2, 

555, 

515.1, 

515.3, 

515.4

D5317–93, 

98 

(Reapproved 

2003)

25. Alachlor2 507, 

525.2, 

508.1, 

505, 

551.1

26. Atrazine2 507, 

525.2, 

508.1, 

505, 

551.1

Syngenta5AG–

625

27. Benzo(a)pyrene 525.2, 

550, 

550.1

28. Carbofuran 531.1, 

531.2

6610

29. Chlordane 508, 

525.2, 

508.1, 

505

30. Dalapon 552.1 

515.1, 

552.2, 

515.3, 

515.4, 

552.3

31. Di(2-ethylhexyl)adipate 506, 

525.2

32. Di(2-ethylhexyl)

phthalate

506, 

525.2

33. Dibromochloropropane 

(DBCP)

504.1, 

551.1

34. Dinoseb4 515.2, 

555, 

515.1, 

515.3, 

515.4

35. Diquat 549.2

36. Endothall 548.1

37. Endrin 508, 

525.2, 

508.1, 

505, 

551.1

38. Ethylene dibromide 

(EDB)

504.1, 

551.1

39. Glyphosate 547 6651

40. Heptachlor 508, 

525.2, 

508.1, 

505, 

551.1

41. Heptachlor Epoxide 508, 

525.2, 

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1[Reserved]

2Substitution of the detector specified in Method 505, 507, 508 or 508.1 for the purpose of achieving 

lower detection limits is allowed as follows. Either an electron capture or nitrogen phosphorous detector 

may be used provided all regulatory requirements and quality control criteria are met. 

3PCBs are qualitatively identified as Aroclors and measured for compliance purposes as 

decachlorobiphenyl. Users of Method 505 may have more difficulty in achieving the required detection 

limits than users of Methods 508.1, 525.2 or 508. 

4Accurate determination of the chlorinated esters requires hydrolysis of the sample as described in EPA 

Methods 515.1, 515.2, 515.3, 515.4 and 555 and ASTM Method D5317–93. 

5This method may not be used for the analysis of atrazine in any system where chlorine dioxide is used 

for drinking water treatment. In samples from all other systems, any result for atrazine generated by 

Method AG–625 that is greater than one-half the maximum contaminant level (MCL) (in other words, 

greater than 0.0015mg/L or 1.5 μg/L) must be confirmed using another approved method for this 

contaminant and should use additional volume of the original sample collected for compliance 

monitoring. In instances where a result from Method AG–625 triggers such confirmatory testing, the 

confirmatory result is to be used to determine compliance. 

(2) [Reserved] 

508.1, 

505, 

551.1

42. Hexachlorobenzene 508, 

525.2, 

508.1, 

505, 

551.1

43. 

Hexachlorocyclopentadiene

508, 

525.2, 

508.1, 

505, 

551.1

44. Lindane 508, 

525.2, 

508.1, 

505, 

551.1

45. Methoxychlor 508, 

525.2, 

508.1, 

505, 

551.1

46. Oxamyl 531.1, 

531.2

6610

47. PCBs3(as 

decachlorobiphenyl)

508A

48. PCBs3(as Aroclors) 508.1, 

508, 

525.2, 

505

49. Pentachlorophenol 515.2, 

525.2, 

555, 

515.1, 

515.3, 

515.4

D5317–93, 

98 

(Reapproved 

2003)

50. Picloram4 515.2, 

555, 

515.1, 

515.3, 

515.4

D5317–93, 

98 

(Reapproved 

2003)

51. Simazine2 507, 

525.2, 

508.1, 

505, 

551.1

52. Toxaphene 508, 

508.1, 

525.2, 

505

53. Total Trihalomethanes 502.2, 

524.2, 

551.1

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(f) Beginning with the initial compliance period, analysis of the contaminants listed in §141.61(a) (1) 

through (21) for the purpose of determining compliance with the maximum contaminant level shall be 

conducted as follows: 

(1) Groundwater systems shall take a minimum of one sample at every entry point to the distribution 

system which is representative of each well after treatment (hereafter called a sampling point). Each 

sample must be taken at the same sampling point unless conditions make another sampling point more 

representative of each source, treatment plant, or within the distribution system. 

(2) Surface water systems (or combined surface/ground) shall take a minimum of one sample at points 

in the distribution system that are representative of each source or at each entry point to the distribution 

system after treatment (hereafter called a sampling point). Each sample must be taken at the same 

sampling point unless conditions make another sampling point more representative of each source, 

treatment plant, or within the distribution system. 

(3) If the system draws water from more than one source and the sources are combined before 

distribution, the system must sample at an entry point to the distribution system during periods of normal 

operating conditions ( i.e. , when water representative of all sources is being used). 

(4) Each community and non-transient non-community water system shall take four consecutive 

quarterly samples for each contaminant listed in §141.61(a) (2) through (21) during each compliance 

period, beginning in the initial compliance period. 

(5) If the initial monitoring for contaminants listed in §141.61(a) (1) through (8) and the monitoring for the 

contaminants listed in §141.61(a) (9) through (21) as allowed in paragraph (f)(18) has been completed 

by December 31, 1992, and the system did not detect any contaminant listed in §141.61(a) (1) through 

(21), then each ground and surface water system shall take one sample annually beginning with the 

initial compliance period. 

(6) After a minimum of three years of annual sampling, the State may allow groundwater systems with 

no previous detection of any contaiminant listed in §141.61(a) to take one sample during each 

compliance period. 

(7) Each community and non-transient non-community ground water system which does not detect a 

contaminant listed in §141.61(a) (1) through (21) may apply to the State for a waiver from the 

requirements of paragraphs (f)(5) and (f)(6) of this section after completing the initial monitoring. (For 

purposes of this section, detection is defined as ≥0.0005 mg/l.) A waiver shall be effective for no more 

than six years (two compliance periods). States may also issue waivers to small systems for the initial 

round of monitoring for 1,2,4-trichlorobenzene. 

(8) A State may grant a waiver after evaluating the following factor(s): 

(i) Knowledge of previous use (including transport, storage, or disposal) of the contaminant within the 

watershed or zone of influence of the system. If a determination by the State reveals no previous use of 

the contaminant within the watershed or zone of influence, a waiver may be granted. 

(ii) If previous use of the contaminant is unknown or it has been used previously, then the following 

factors shall be used to determine whether a waiver is granted. 

(A) Previous analytical results. 

(B) The proximity of the system to a potential point or non-point source of contamination. Point sources 

include spills and leaks of chemicals at or near a water treatment facility or at manufacturing, 

distribution, or storage facilities, or from hazardous and municipal waste landfills and other waste 

handling or treatment facilities. 

(C) The environmental persistence and transport of the contaminants. 

(D) The number of persons served by the public water system and the proximity of a smaller system to a 

larger system. 

(E) How well the water source is protected against contamination, such as whether it is a surface or 

groundwater system. Groundwater systems must consider factors such as depth of the well, the type of 

soil, and wellhead protection. Surface water systems must consider watershed protection. 

(9) As a condition of the waiver a groundwater system must take one sample at each sampling point 

during the time the waiver is effective ( i.e. , one sample during two compliance periods or six years) and 

update its vulnerability assessment considering the factors listed in paragraph (f)(8) of this section. 

Based on this vulnerability assessment the State must reconfirm that the system is non-vulnerable. If the 

State does not make this reconfirmation within three years of the initial determination, then the waiver is 

invalidated and the system is required to sample annually as specified in paragraph (5) of this section. 

(10) Each community and non-transient non-community surface water system which does not detect a 

contaminant listed in §141.61(a) (1) through (21) may apply to the State for a waiver from the 

requirements of (f)(5) of this section after completing the initial monitoring. Composite samples from a 

maximum of five sampling points are allowed, provided that the detection limit of the method used for 

analysis is less than one-fifth of the MCL. Systems meeting this criterion must be determined by the 

State to be non-vulnerable based on a vulnerability assessment during each compliance period. Each 

system receiving a waiver shall sample at the frequency specified by the State (if any). 

(11) If a contaminant listed in §141.61(a) (2) through (21) is detected at a level exceeding 0.0005 mg/l in 

any sample, then: 

(i) The system must monitor quarterly at each sampling point which resulted in a detection. 

(ii) The State may decrease the quarterly monitoring requirement speci fied in paragraph (f)(11)(i) of this 

section provided it has determined that the system is reliably and consistently below the maximum 

contaminant level. In no case shall the State make this determination unless a groundwater system 

takes a minimum of two quarterly samples and a surface water system takes a minimum of four 

quarterly samples. 

(iii) If the State determines that the system is reliably and consistently below the MCL, the State may 

allow the system to monitor annually. Systems which monitor annually must monitor during the quarter

(s) which previously yielded the highest analytical result. 

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(iv) Systems which have three consecutive annual samples with no detection of a contaminant may 

apply to the State for a waiver as specified in paragraph (f)(7) of this section. 

(v) Groundwater systems which have detected one or more of the following two-carbon organic 

compounds: trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, cis-1,2-

dichloroethylene, trans-1,2-dichloroethylene, or 1,1-dichloroethylene shall monitor quarterly for vinyl 

chloride. A vinyl chloride sample shall be taken at each sampling point at which one or more of the twocarbon organic compounds was detected. If the results of the first analysis do not detect vinyl chloride, 

the State may reduce the quarterly monitoring frequency of vinyl chloride monitoring to one sample 

during each compliance period. Surface water systems are required to monitor for vinyl chloride as 

specified by the State. 

(12) Systems which violate the requirements of §141.61(a) (1) through (21), as determined by paragraph 

(f)(15) of this section, must monitor quarterly. After a minimum of four consecutive quarterly samples 

which show the system is in compliance as specified in paragraph (f)(15) of this section the system and 

the State determines that the system is reliably and consistently below the maximum contaminant level, 

the system may monitor at the frequency and times specified in paragraph (f)(11)(iii) of this section. 

(13) The State may require a confirmation sample for positive or negative results. If a confirmation 

sample is required by the State, the result must be averaged with the first sampling result and the 

average is used for the compliance determination as specified by paragraph (f)(15). States have 

discretion to delete results of obvious sampling errors from this calculation. 

(14) The State may reduce the total number of samples a system must analyze by allowing the use of 

compositing. Composite samples from a maximum of five sampling points are allowed, provided that the 

detection limit of the method used for analysis is less than one-fifth of the MCL. Compositing of samples 

must be done in the laboratory and analyzed within 14 days of sample collection. 

(i) If the concentration in the composite sample is greater than or equal to 0.0005 mg/l for any 

contaminant listed in §141.61(a), then a follow-up sample must be taken within 14 days at each 

sampling point included in the composite, and be analyzed for that contaminant. 

(ii) If duplicates of the original sample taken from each sampling point used in the composite sample are 

available, the system may use these instead of resampling. The duplicates must be analyzed and the 

results reported to the State within 14 days after completing analysis of the composite sample, provided 

the holding time of the sample is not exceeded. 

(iii) If the population served by the system is > 3,300 persons, then compositing may only be permitted 

by the State at sampling points within a single system. In systems serving ≤ 3,300 persons, the State 

may permit compositing among different systems provided the 5-sample limit is maintained. 

(iv) Compositing samples prior to GC analysis. 

(A) Add 5 ml or equal larger amounts of each sample (up to 5 samples are allowed) to a 25 ml glass 

syringe. Special precautions must be made to maintain zero headspace in the syringe. 

(B) The samples must be cooled at 4 °C during this step to minimize volatilization losses. 

(C) Mix well and draw out a 5-ml aliquot for analysis. 

(D) Follow sample introduction, purging, and desorption steps described in the method. 

(E) If less than five samples are used for compositing, a proportionately small syringe may be used. 

(v) Compositing samples prior to GC/MS analysis. 

(A) Inject 5-ml or equal larger amounts of each aqueous sample (up to 5 samples are allowed) into a 25-

ml purging device using the sample introduction technique described in the method. 

(B) The total volume of the sample in the purging device must be 25 ml. 

(C) Purge and desorb as described in the method. 

(15) Compliance with §141.61(a) (1) through (21) shall be determined based on the analytical results 

obtained at each sampling point. If one sampling point is in violation of an MCL, the system is in violation 

of the MCL. 

(i) For systems monitoring more than once per year, compliance with the MCL is determined by a 

running annual average at each sampling point. 

(ii) Systems monitoring annually or less frequently whose sample result exceeds the MCL must begin 

quarterly sampling. The system will not be considered in violation of the MCL until it has completed one 

year of quarterly sampling. 

(iii) If any sample result will cause the running annual average to exceed the MCL at any sampling point, 

the system is out of compliance with the MCL immediately. 

(iv) If a system fails to collect the required number of samples, compliance will be based on the total 

number of samples collected. 

(v) If a sample result is less than the detection limit, zero will be used to calculate the annual average. 

(16) [Reserved] 

(17) Analysis under this section shall only be conducted by laboratories that are certified by EPA or the 

State according to the following conditions (laboratories may conduct sample analysis under provisional 

certification until January 1, 1996): 

(i) To receive certification to conduct analyses for the contaminants in §141.61(a) (2) through (21) the 

laboratory must: 

(A) Analyze Performance Evaluation (PE) samples provided by EPA, the State, or by a third party (with 

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the approval of the State or EPA) at least once a year by each method for which the laboratory desires 

certification. 

(B) Achieve the quantitative acceptance limits under paragraphs (f)(17)(i)(C) and (D) of this section for at 

least 80 percent of the regulated organic contaminants included in the PE sample. 

(C) Achieve quantitative results on the analyses performed under paragraph (f)(17)(i)(A) of this section 

that are within ±20% of the actual amount of the substances in the Performance Evaluation sample 

when the actual amount is greater than or equal to 0.010 mg/l. 

(D) Achieve quantitative results on the analyses performed under paragraph (f)(17)(i)(A) of this section 

that are within ±40 percent of the actual amount of the substances in the Performance Evaluation 

sample when the actual amount is less than 0.010 mg/l. 

(E) Achieve a method detection limit of 0.0005 mg/l, according to the procedures in appendix B of part 

136. 

(ii) To receive certification to conduct analyses for vinyl chloride, the laboratory must: 

(A) Analyze Performance Evaluation (PE) samples provided by EPA, the State, or by a third party (with 

the approval of the State or EPA) at least once a year by each method for which the laboratory desires 

certification. 

(B) Achieve quantitative results on the analyses performed under paragraph (f)(17)(ii)(A) of this section 

that are within ±40 percent of the actual amount of vinyl chloride in the Performance Evaluation sample. 

(C) Achieve a method detection limit of 0.0005 mg/l, according to the procedures in appendix B of part 

136. 

(D) Obtain certification for the contaminants listed in §141.61(a)(2) through (21). 

(18) States may allow the use of monitoring data collected after January 1, 1988, required under section 

1445 of the Act for purposes of initial monitoring compliance. If the data are generally consistent with the 

other requirements of this section, the State may use these data ( i.e. , a single sample rather than four 

quarterly samples) to satisfy the initial monitoring requirement of paragraph (f)(4) of this section. 

Systems which use grandfathered samples and did not detect any contaminant listed §141.61(a)(2) 

through (21) shall begin monitoring annually in accordance with paragraph (f)(5) of this section 

beginning with the initial compliance period. 

(19) States may increase required monitoring where necessary to detect variations within the system. 

(20) Each certified laboratory must determine the method detection limit (MDL), as defined in appendix B 

to part 136, at which it is capable of detecting VOCs. The acceptable MDL is 0.0005 mg/l. This 

concentration is the detection concentration for purposes of this section. 

(21) Each public water system shall monitor at the time designated by the State within each compliance 

period. 

(22) All new systems or systems that use a new source of water that begin operation after January 22, 

2004 must demonstrate compliance with the MCL within a period of time specified by the State. The 

system must also comply with the initial sampling frequencies specified by the State to ensure a system 

can demonstrate compliance with the MCL. Routine and increased monitoring frequencies shall be 

conducted in accordance with the requirements in this section. 

(g) [Reserved] 

(h) Analysis of the contaminants listed in §141.61(c) for the purposes of determining compliance with the 

maximum contaminant level shall be conducted as follows, with the exception that no monitoring is 

required for aldicarb, aldicarb sulfoxide or aldicarb sulfone: 

(1) Groundwater systems shall take a minimum of one sample at every entry point to the distribution 

system which is representative of each well after treatment (hereafter called a sampling point). Each 

sample must be taken at the same sampling point unless conditions make another sampling point more 

representative of each source or treatment plant. 

(2) Surface water systems shall take a minimum of one sample at points in the distribution system that 

are representative of each source or at each entry point to the distribution system after treatment 

(hereafter called a sampling point). Each sample must be taken at the same sampling point unless 

conditions make another sampling point more representative of each source or treatment plant. 

Note: For purposes of this paragraph, surface water systems include systems with a 

combination of surface and ground sources.

(3) If the system draws water from more than one source and the sources are combined before 

distribution, the system must sample at an entry point to the distribution system during periods of normal 

operating conditions ( i.e. , when water representative of all sources is being used). 

(4) Monitoring frequency: (i) Each community and non-transient non-community water system shall take 

four consecutive quarterly samples for each contaminant listed in §141.61(c) during each compliance 

period beginning with the initial compliance period. 

(ii) Systems serving more than 3,300 persons which do not detect a contaminant in the initial compliance 

period may reduce the sampling frequency to a minimum of two quarterly samples in one year during 

each repeat compliance period. 

(iii) Systems serving less than or equal to 3,300 persons which do not detect a contaminant in the initial 

compliance period may reduce the sampling frequency to a minimum of one sample during each repeat 

compliance period. 

(5) Each community and non-transient water system may apply to the State for a waiver from the 

requirement of paragraph (h)(4) of this section. A system must reapply for a waiver for each compliance 

period. 

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(6) A State may grant a waiver after evaluating the following factor(s): Knowledge of previous use 

(including transport, storage, or disposal) of the contaminant within the watershed or zone of influence of 

the system. If a determination by the State reveals no previous use of the contaminant within the 

watershed or zone of influence, a waiver may be granted. If previous use of the contaminant is unknown 

or it has been used previously, then the following factors shall be used to determine whether a waiver is 

granted. 

(i) Previous analytical results. 

(ii) The proximity of the system to a potential point or non-point source of contamination. Point sources 

include spills and leaks of chemicals at or near a water treatment facility or at manufacturing, 

distribution, or storage facilities, or from hazardous and municipal waste landfills and other waste 

handling or treatment facilities. Non-point sources include the use of pesticides to control insect and 

weed pests on agricultural areas, forest lands, home and gardens, and other land application uses. 

(iii) The environmental persistence and transport of the pesticide or PCBs. 

(iv) How well the water source is protected against contamination due to such factors as depth of the 

well and the type of soil and the integrity of the well casing. 

(v) Elevated nitrate levels at the water supply source. 

(vi) Use of PCBs in equipment used in the production, storage, or distribution of water ( i.e. , PCBs used 

in pumps, transformers, etc.). 

(7) If an organic contaminant listed in §141.61(c) is detected (as defined by paragraph (h)(18) of this 

section) in any sample, then: 

(i) Each system must monitor quarterly at each sampling point which resulted in a detection. 

(ii) The State may decrease the quarterly monitoring requirement specified in paragraph (h)(7)(i) of this 

section provided it has determined that the system is reliably and consistently below the maximum 

contaminant level. In no case shall the State make this determination unless a groundwater system 

takes a minimum of two quarterly samples and a surface water system takes a minimum of four 

quarterly samples. 

(iii) After the State determines the system is reliably and consistently below the maximum contaminant 

level the State may allow the system to monitor annually. Systems which monitor annually must monitor 

during the quarter that previously yielded the highest analytical result. 

(iv) Systems which have 3 consecutive annual samples with no detection of a contaminant may apply to 

the State for a waiver as specified in paragraph (h)(6) of this section. 

(v) If the monitoring results in detection of one or more of certain related contaminants (heptachlor and 

heptachlor epoxide), then subsequent monitoring shall analyze for all related contaminants. 

(8) Systems which violate the requirements of §141.61(c) as determined by paragraph (h)(11) of this 

section must monitor quarterly. After a minimum of four quarterly samples show the system is in 

compliance and the State determines the system is reliably and consistently below the MCL, as 

specified in paragraph (h)(11) of this section, the system shall monitor at the frequency specified in 

paragraph (h)(7)(iii) of this section. 

(9) The State may require a confirmation sample for positive or negative results. If a confirmation sample 

is required by the State, the result must be averaged with the first sampling result and the average used 

for the compliance determination as specified by paragraph (h)(11) of this section. States have 

discretion to delete results of obvious sampling errors from this calculation. 

(10) The State may reduce the total number of samples a system must analyze by allowing the use of 

compositing. Composite samples from a maximum of five sampling points are allowed, provided that the 

detection limit of the method used for analysis is less than one-fifth of the MCL. Compositing of samples 

must be done in the laboratory and analyzed within 14 days of sample collection. 

(i) If the concentration in the composite sample detects one or more contaminants listed in §141.61(c), 

then a follow-up sample must be taken within 14 days at each sampling point included in the composite, 

and be analyzed for that contaminant. 

(ii) If duplicates of the original sample taken from each sampling point used in the composite sample are 

available, the system may use these instead of resampling. The duplicates must be analyzed and the 

results reported to the State within 14 days after completion of the composite analysis or before the 

holding time for the initial sample is exceeded whichever is sooner. 

(iii) If the population served by the system is >3,300 persons, then compositing may only be permitted by 

the State at sampling points within a single system. In systems serving ≤ 3,300 persons, the State may 

permit compositing among different systems provided the 5-sample limit is maintained. 

(11) Compliance with §141.61(c) shall be determined based on the analytical results obtained at each 

sampling point. If one sampling point is in violation of an MCL, the system is in violation of the MCL. 

(i) For systems monitoring more than once per year, compliance with the MCL is determined by a 

running annual average at each sampling point. 

(ii) Systems monitoring annually or less frequently whose sample result exceeds the regulatory detection 

level as defined by paragraph (h)(18) of this section must begin quarterly sampling. The system will not 

be considered in violation of the MCL until it has completed one year of quarterly sampling. 

(iii) If any sample result will cause the running annual average to exceed the MCL at any sampling point, 

the system is out of compliance with the MCL immediately. 

(iv) If a system fails to collect the required number of samples, compliance will be based on the total 

number of samples collected. 

(v) If a sample result is less than the detection limit, zero will be used to calculate the annual average. 

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(12) [Reserved] 

(13) Analysis for PCBs shall be conducted as follows using the methods in paragraph (e) of this section: 

(i) Each system which monitors for PCBs shall analyze each sample using either Method 508.1, 525.2, 

508 or 505. Users of Method 505 may have more difficulty in achieving the required Aroclor detection 

limits than users of Methods 508.1, 525.2 or 508. 

(ii) If PCBs (as one of seven Aroclors) are detected (as designated in this paragraph) in any sample 

analyzed using Method 505 or 508, the system shall reanalyze the sample using Method 508A to 

quantitate PCBs (as decachlorobiphenyl). 

(iii) Compliance with the PCB MCL shall be determined based upon the quantitative results of analyses 

using Method 508A. 

(14) If monitoring data collected after January 1, 1990, are generally consistent with the requirements of 

§141.24(h), then the State may allow systems to use that data to satisfy the monitoring requirement for 

the initial compliance period beginning January 1, 1993. 

(15) The State may increase the required monitoring frequency, where necessary, to detect variations 

within the system (e.g., fluctuations in concentration due to seasonal use, changes in water source). 

(16) The State has the authority to determine compliance or initiate enforcement action based upon 

analytical results and other information compiled by their sanctioned representatives and agencies. 

(17) Each public water system shall monitor at the time designated by the State within each compliance 

period. 

(18) Detection as used in this paragraph shall be defined as greater than or equal to the following 

concentrations for each contaminant. 

Aroclor Detection limit (mg/l)

1016 0.00008

1221 0.02

1232 0.0005

1242 0.0003

1248 0.0001

1254 0.0001

1260 0.0002

Contaminant

Detection limit 

(mg/l)

Alachlor .0002

Aldicarb .0005

Aldicarb sulfoxide .0005

Aldicarb sulfone .0008

Atrazine .0001

Benzo[a]pyrene .00002

Carbofuran .0009

Chlordane .0002

Dalapon .001

1,2–Dibromo–3–chloropropane (DBCP) .00002

Di (2-ethylhexyl) adipate .0006

Di (2-ethylhexyl) phthalate .0006

Dinoseb .0002

Diquat .0004

2,4-D .0001

Endothall .009

Endrin .00001

Ethylene dibromide (EDB) .00001

Glyphosate .006

Heptachlor .00004

Heptachlor epoxide .00002

Hexachlorobenzene .0001

Hexachlorocyclopentadiene .0001

Lindane .00002

Methoxychlor .0001

Oxamyl .002

Picloram .0001

Polychlorinated biphenyls (PCBs) (as 

decachlorobiphenyl)

.0001

Pentachlorophenol .00004

Simazine .00007

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(19) Anaylsis under this section shall only be conducted by laboratories that have received certification 

by EPA or the State and have met the following conditions: 

(i) To receive certification to conduct analyses for the contaminants in §141.61(c) the laboratory must: 

(A) Analyze Performance Evaluation (PE) samples provided by EPA, the State, or by a third party (with 

the approval of the State or EPA) at least once a year by each method for which the laboratory desires 

certification. 

(B) For each contaminant that has been included in the PE sample achieve quantitative results on the 

analyses that are within the following acceptance limits: 

(ii) [Reserved] 

(20) All new systems or systems that use a new source of water that begin operation after January 22, 

2004 must demonstrate compliance with the MCL within a period of time specified by the State. The 

system must also comply with the initial sampling frequencies specified by the State to ensure a system 

can demonstrate compliance with the MCL. Routine and increased monitoring frequencies shall be 

conducted in accordance with the requirements in this section. 

(Approved by the Office of Management and Budget under control number 2040–0090) 

[40 FR 59570, Dec. 24, 1975] 

Editorial Note: For Federal Register citations affecting §141.24, see the List of CFR Sections 

Affected, which appears in the Finding Aids section of the printed volume and at www.fdsys.gov. 

§ 141.25 Analytical methods for radioactivity. 

 top

(a) Analysis for the following contaminants shall be conducted to determine compliance with §141.66 

(radioactivity) in accordance with the methods in the following table, or the alternative methods listed in 

appendix A to subpart C this part, or their equivalent determined by EPA in accordance with §141.27. 

Toxaphene .001

2,3,7,8-TCDD (Dioxin) .000000005

2,4,5-TP (Silvex) .0002

Contaminant Acceptance limits (percent)

DBCP ±40

EDB ±40.

Alachlor ±45.

Atrazine ±45.

Benzo[a]pyrene 2 standard deviations.

Carbofuran ±45.

Chlordane ±45.

Dalapon 2 standard deviations.

Di(2-ethylhexyl)adipate 2 standard deviations.

Di(2-ethylhexyl)phthalate 2 standard deviations.

Dinoseb 2 standard deviations.

Diquat 2 standard deviations.

Endothall 2 standard deviations.

Endrin ±30.

Glyphosate 2 standard deviations.

Heptachlor ±45.

Heptachlor epoxide ±45.

Hexachlorobenzene 2 standard deviations.

Hexachloro- cyclopentadiene 2 standard deviations.

Lindane ±45.

Methoxychlor ±45.

Oxamyl 2 standard deviations.

PCBs (as Decachlorobiphenyl) 0–200.

Picloram 2 standard deviations.

Simazine 2 standard deviations.

Toxaphene ±45.

Aldicarb 2 standard deviations.

Aldicarb sulfoxide 2 standard deviations.

Aldicarb sulfone 2 standard deviations.

Pentachlorophenol ±50.

2,3,7,8-TCDD (Dioxin) 2 standard deviations.

2,4-D ±50.

2,4,5-TP (Silvex) ±50.

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Contaminant Methodology

Reference (Method of Page Number)

EPA1 EPA2 EPA3 EPA4 SM5 ASTM6 USGS7 DOE8 Other

Naturally Occurring:

Gross 

alpha11and 

beta

Evaporation 900.0 p. 1 00–

01

p. 1 302, 

7110 

B, 

7110 

B–00

R–

1120–

76

Gross 

alpha11

Coprecipitation 00–

02

7110 

C, 

7110 

C–00

Radium 

226

Radon 

emanation

903.1 p. 16 Ra–

04

p. 19 305, 

7500–

Ra C, 

7500–

Ra 

C–01

D3454–97 R–

1141–

76

Ra-04 NY9,

 Radiochemical 903.0 p. 13 Ra03304, 

7500–

Ra B, 

7500–

Ra B–

01

D2460–97 R–

1140–

76

GA14

Radium 

228

Radiochemical 904.0 p. 24 Ra05p. 19 7500–

Ra D, 

7500–

Ra 

D–01

R–

1142–

76

NY9,

NJ10,

GA14

Uranium12 Radiochemical 908.0 7500–

U B, 

7500–

U B–

00

 Fluorometric 908.1 7500–

U C 

(17th 

Ed.)

D2907–97 R–

1180–

76, R–

1181–

76

U–04

 ICP–MS 200.813 3125 D5673–03

 Alpha 

Spectrometry

00–

07

p. 33 7500–

U C 

(18th, 

19th, 

or 

20th 

Ed.), 

7500–

U C–

00

D3972–97, 

02

R–

1182–

76

U–02

 Laser 

Phosphorimetry

D5174–97, 

02

Man-Made:

Radioactive 

Cesium

Radiochemical 901.0 p. 4 7500–

Cs B, 

7500–

Cs B–

00

D2459–72 R–

1111–

76

 Gamma Ray 

Spectrometry

901.1 p. 92 7120, 

7120–

97

D3649–91, 

98a

R–

1110–

76

4.5.2.3

Radioactive 

Iodine

Radiochemical 902.0 p. 6 7500–

I B, 

7500–

I B–

00

 p. 9 7500–

I C, 

7500–

I C–

00

 7500– D3649–91, 

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The procedures shall be done in accordance with the documents listed below. The incorporation by 

reference of documents 1 through 10 and 13 through 14 was approved by the Director of the Federal 

Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the documents may be 

obtained from the sources listed below. Information regarding obtaining these documents can be 

obtained from the Safe Drinking Water Hotline at 800–426–4791. Documents may be inspected at 

EPA's Drinking Water Docket, EPA West, 1301 Constitution Avenue, NW., Room 3334 , Washington, 

DC 20460 (Telephone: 202–566–2426); or at the National Archives and Records Administration (NARA). 

For information on the availability of this material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

1“Prescribed Procedures for the Measurement of Radioactivity in Drinking Water,” EPA 600/4–80–032, 

August 1980. Available at the U.S. Department of Commerce, National Technical Information Service 

(NTIS), 5285 Port Royal Road, Springfield, VA 22161 (Telephone 800–553–6847), PB 80–224744. 

2“Interim Radiochemical Methodology for Drinking Water,” EPA 600/4–75–008 (revised), March 1976. 

Available NTIS, ibid. 

3“Radiochemistry Procedures Manual,” EPA 520/5–84–006, December 1987. Available NTIS, ibid.

4“Radiochemical Analytical Procedures for Analysis of Environmental Samples,” March 1979. Available 

at NTIS, ibid. EMSL LV 053917. 

5“Standard Methods for the Examination of Water and Wastewater,” 13th, 17th, 18th, 19th or 20th 

edition, 1971, 1989, 1992, 1995, 1998. Available at American Public Health Association, 1015 Fifteenth 

Street, NW., Washington, DC 20005. Methods 302, 303, 304, 305 and 306 are only in the 13th edition. 

Methods 7110B, 7500–Ra B, 7500–Ra C, 7500–Ra D, 7500–U B, 7500–Cs B, 7500–I B, 7500–I C, 

7500–I D, 7500–Sr B, and 7500–3H B are in the 17th, 18th, 19th and 20th editions. Method 7110 C is in 

the 18th, 19th and 20th editions. Method 7500–U C Fluorometric Uranium is only in the 17th Edition, and 

7500–U C Alpha spectrometry is only in the 18th, 19th and 20th editions. Method 7120 is only in the 

19th and 20th editions. Method 3125 is only in the 20th edition. Methods 7110 B–00, 7110 C–00, 7500–

Ra B–01, 7500–Ra C–01, 7500–Ra D–01, 7500–U B–00, 7500–U C–00, 7500–I B–00, 7500–I C–00, 

7500–I D–00, 7120–97, 7500–Sr B–01, and 7500–3H B–00 are available online at 

http://www.standardmethods.org. The year in which each method was approved by the Standard 

Methods Committee is designated by the last two digits in the method number. The methods listed are 

the only online versions that may be used. 

6 Annual Book of ASTM Standards, Vol. 11.01 and 11.02, 2002; ASTM International; any year 

containing the cited version of the method may be used. Copies of these two volumes and the 2003 

version of D 5673–03 may be obtained from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, 

West Conshohocken, PA 19428–2959. 

7“Methods for Determination of Radioactive Substances in Water and Fluvial Sediments,” Chapter A5 in 

Book 5 of Techniques of Water-Resources Investigations of the United States Geological Survey, 1977. 

Available at U.S. Geological Survey (USGS) Information Services, Box 25286, Federal Center, Denver, 

CO 80225–0425. 

8“EML Procedures Manual,” 28th (1997) or 27th (1990) Editions, Volumes 1 and 2; either edition may be 

used. In the 27th Edition Method Ra-04 is listed as Ra-05 and Method Ga-01–R is listed as Sect. 

4.5.2.3. Available at the Environmental Measurements Laboratory, U.S. Department of Energy (DOE), 

376 Hudson Street, New York, NY 10014–3621. 

I D, 

7500–

I D–

00

98a

 Gamma Ray 

Spectrometry

901.1 p. 92 7120, 

7120–

97

D4785–93, 

00a

4.5.2.3

Radioactive 

Strontium 

89, 90

Radiochemical 905.0 p. 29 Sr–

04

p. 65 303, 

7500–

Sr B, 

7500–

Sr B–

01

R–

1160–

76

Sr–01, 

Sr–02

Tritium Liquid 

Scintillation

906.0 p. 34 H–02 p. 87 306, 

7500–

3H B, 

7500–

3H B–

00

D4107–91, 

98 

(Reapproved 

2002)

R–

1171–

76

Gamma 

Emitters

Gamma Ray 

Spectrometry

901.1 p. 92 7120, 

7120–

97

D3649–91, 

98a

R–

1110–

76

Ga–

01–R

 902.0 7500–

Cs B, 

7500–

Cs B–

00

D4785–93, 

00a

 901.0 7500–

I B, 

7500–

I B–

00

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9“Determination of Ra–226 and Ra–228 (Ra–02),” January 1980, Revised June 1982. Available at 

Radiological Sciences Institute for Laboratories and Research, New York State Department of Health, 

Empire State Plaza, Albany, NY 12201. 

10“Determination of Radium 228 in Drinking Water,” August 1980. Available at State of New Jersey, 

Department of Environmental Protection, Division of Environmental Quality, Bureau of Radiation and 

Inorganic Analytical Services, 9 Ewing Street, Trenton, NJ 08625. 

11Natural uranium and thorium-230 are approved as gross alpha calibration standards for gross alpha 

with co-precipitation and evaporation methods; americium-241 is approved with co-precipitation 

methods. 

12If uranium (U) is determined by mass, a 0.67 pCi/μg of uranium conversion factor must be used. This 

conversion factor is based on the 1:1 activity ratio of U–234 and U–238 that is characteristic of naturally 

occurring uranium. 

13“Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma-Mass 

Spectrometry,” Revision 5.4, which is published in “Methods for the Determination of Metals in 

Environmental Samples—Supplement I,”' EPA 600–R–94–111, May 1994. Available at NTIS, PB 95–

125472. 

14“The Determination of Radium-226 and Radium-228 in Drinking Water by Gamma-ray Spectrometry 

Using HPGE or Ge(Li) Detectors,” Revision 1.2, December 2004. Available from the Environmental 

Resources Center, Georgia Institute of Technology, 620 Cherry Street, Atlanta, GA 30332–0335, USA, 

Telephone: 404–894–3776. This method may be used to analyze for radium-226 and radium-228 in 

samples collected after January 1, 2005 to satisfy the radium-226 and radium-228 monitoring 

requirements specified at 40 CFR 141.26. 

(b) When the identification and measurement of radionuclides other than those listed in paragraph (a) of 

this section is required, the following references are to be used, except in cases where alternative 

methods have been approved in accordance with §141.27. 

(1) Procedures for Radiochemical Analysis of Nuclear Reactor Aqueous Solutions, H. L. Krieger and S. 

Gold, EPA-R4–73–014. USEPA, Cincinnati, Ohio, May 1973. 

(2) HASL Procedure Manual, Edited by John H. Harley. HASL 300, ERDA Health and Safety Laboratory, 

New York, NY., 1973. 

(c) For the purpose of monitoring radioactivity concentrations in drinking water, the required sensitivity of 

the radioanalysis is defined in terms of a detection limit. The detection limit shall be that concentration 

which can be counted with a precision of plus or minus 100 percent at the 95 percent confidence level 

(1.96σ where σ is the standard deviation of the net counting rate of the sample). 

(1) To determine compliance with §141.66(b), (c), and (e) the detection limit shall not exceed the 

concentrations in Table B to this paragraph. 

Table B—Detection Limits for Gross Alpha Particle Activity, Radium 226, Radium 228, and 

Uranium 

(2) To determine compliance with §141.66(d) the detection limits shall not exceed the concentrations 

listed in Table C to this paragraph. 

Table C—Detection Limits for Man-made Beta Particle and Photon Emitters 

(d) To judge compliance with the maximum contaminant levels listed in §141.66, averages of data shall 

be used and shall be rounded to the same number of significant figures as the maximum contaminant 

level for the substance in question. 

(e) The State has the authority to determine compliance or initiate enforcement action based upon 

analytical results or other information compiled by their sanctioned representatives and agencies. 

[41 FR 28404, July 9, 1976, as amended at 45 FR 57345, Aug. 27, 1980; 62 FR 10173, Mar. 5, 1997; 65 

FR 76745, Dec. 7, 2000; 67 FR 65250, Oct. 23, 2002; 69 FR 38855, June 29, 2004; 69 FR 52180, Aug. 

25, 2004; 72 FR 11245, Mar. 12, 2007; 74 FR 30958, June 29, 2009] 

§ 141.26 Monitoring frequency and compliance requirements for radionuclides in 

community water systems. 

Contaminant

Detection 

limit

Gross alpha particle activity 3 pCi/L.

Radium 226 1 pCi/L.

Radium 228 1 pCi/L.

Uranium 1 μg/L

Radionuclide Detection limit

Tritium 1,000 pCi/1.

Strontium–89 10 pCi/1.

Strontium–90 2 pCi/1.

Iodine–131 1 pCi/1.

Cesium–134 10 pCi/1.

Gross beta 4 pCi/1.

Other radionuclides 1/10 of the applicable limit.

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 top

(a) Monitoring and compliance requirements for gross alpha particle activity, radium-226, radium-228, 

and uranium. (1) Community water systems (CWSs) must conduct initial monitoring to determine 

compliance with §141.66(b), (c), and (e) by December 31, 2007. For the purposes of monitoring for 

gross alpha particle activity, radium-226, radium-228, uranium, and beta particle and photon radioactivity 

in drinking water, “detection limit” is defined as in §141.25(c). 

(i) Applicability and sampling location for existing community water systems or sources. All existing 

CWSs using ground water, surface water or systems using both ground and surface water (for the 

purpose of this section hereafter referred to as systems) must sample at every entry point to the 

distribution system that is representative of all sources being used (hereafter called a sampling point) 

under normal operating conditions. The system must take each sample at the same sampling point 

unless conditions make another sampling point more representative of each source or the State has 

designated a distribution system location, in accordance with paragraph (a)(2)(ii)(C) of this section. 

(ii) Applicability and sampling location for new community water systems or sources. All new CWSs or 

CWSs that use a new source of water must begin to conduct initial monitoring for the new source within 

the first quarter after initiating use of the source. CWSs must conduct more frequent monitoring when 

ordered by the State in the event of possible contamination or when changes in the distribution system 

or treatment processes occur which may increase the concentration of radioactivity in finished water. 

(2) Initial monitoring: Systems must conduct initial monitoring for gross alpha particle activity, radium226, radium-228, and uranium as follows: 

(i) Systems without acceptable historical data, as defined below, must collect four consecutive quarterly 

samples at all sampling points before December 31, 2007. 

(ii) Grandfathering of data: States may allow historical monitoring data collected at a sampling point to 

satisfy the initial monitoring requirements for that sampling point, for the following situations. 

(A) To satisfy initial monitoring requirements, a community water system having only one entry point to 

the distribution system may use the monitoring data from the last compliance monitoring period that 

began between June 2000 and December 8, 2003. 

(B) To satisfy initial monitoring requirements, a community water system with multiple entry points and 

having appropriate historical monitoring data for each entry point to the distribution system may use the 

monitoring data from the last compliance monitoring period that began between June 2000 and 

December 8, 2003. 

(C) To satisfy initial monitoring requirements, a community water system with appropriate historical data 

for a representative point in the distribution system may use the monitoring data from the last 

compliance monitoring period that began between June 2000 and December 8, 2003, provided that the 

State finds that the historical data satisfactorily demonstrate that each entry point to the distribution 

system is expected to be in compliance based upon the historical data and reasonable assumptions 

about the variability of contaminant levels between entry points. The State must make a written finding 

indicating how the data conforms to the these requirements. 

(iii) For gross alpha particle activity, uranium, radium-226, and radium-228 monitoring, the State may 

waive the final two quarters of initial monitoring for a sampling point if the results of the samples from the 

previous two quarters are below the detection limit. 

(iv) If the average of the initial monitoring results for a sampling point is above the MCL, the system must 

collect and analyze quarterly samples at that sampling point until the system has results from four 

consecutive quarters that are at or below the MCL, unless the system enters into another schedule as 

part of a formal compliance agreement with the State. 

(3) Reduced monitoring: States may allow community water systems to reduce the future frequency of 

monitoring from once every three years to once every six or nine years at each sampling point, based on 

the following criteria. 

(i) If the average of the initial monitoring results for each contaminant ( i.e., gross alpha particle activity, 

uranium, radium-226, or radium-228) is below the detection limit specified in Table B, in §141.25(c)(1), 

the system must collect and analyze for that contaminant using at least one sample at that sampling 

point every nine years. 

(ii) For gross alpha particle activity and uranium, if the average of the initial monitoring results for each 

contaminant is at or above the detection limit but at or below1/2the MCL, the system must collect and 

analyze for that contaminant using at least one sample at that sampling point every six years. For 

combined radium-226 and radium-228, the analytical results must be combined. If the average of the 

combined initial monitoring results for radium-226 and radium-228 is at or above the detection limit but at 

or below1/2the MCL, the system must collect and analyze for that contaminant using at least one 

sample at that sampling point every six years. 

(iii) For gross alpha particle activity and uranium, if the average of the initial monitoring results for each 

contaminant is above1/2the MCL but at or below the MCL, the system must collect and analyze at least 

one sample at that sampling point every three years. For combined radium-226 and radium-228, the 

analytical results must be combined. If the average of the combined initial monitoring results for radium226 and radium-228 is above1/2the MCL but at or below the MCL, the system must collect and analyze 

at least one sample at that sampling point every three years. 

(iv) Systems must use the samples collected during the reduced monitoring period to determine the 

monitoring frequency for subsequent monitoring periods (e.g., if a system's sampling point is on a nine 

year monitoring period, and the sample result is above1/2MCL, then the next monitoring period for that 

sampling point is three years). 

(v) If a system has a monitoring result that exceeds the MCL while on reduced monitoring, the system 

must collect and analyze quarterly samples at that sampling point until the system has results from four 

consecutive quarters that are below the MCL, unless the system enters into another schedule as part of 

a formal compliance agreement with the State. 

(4) Compositing: To fulfill quarterly monitoring requirements for gross alpha particle activity, radium-226, 

radium-228, or uranium, a system may composite up to four consecutive quarterly samples from a single 

entry point if analysis is done within a year of the first sample. States will treat analytical results from the 

composited as the average analytical result to determine compliance with the MCLs and the future 

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monitoring frequency. If the analytical result from the composited sample is greater than1/2MCL, the 

State may direct the system to take additional quarterly samples before allowing the system to sample 

under a reduced monitoring schedule. 

(5) A gross alpha particle activity measurement may be substituted for the required radium-226 

measurement provided that the measured gross alpha particle activity does not exceed 5 pCi/l. A gross 

alpha particle activity measurement may be substituted for the required uranium measurement provided 

that the measured gross alpha particle activity does not exceed 15 pCi/l. The gross alpha measurement 

shall have a confidence interval of 95% (1.65σ, where σ is the standard deviation of the net counting 

rate of the sample) for radium-226 and uranium. When a system uses a gross alpha particle activity 

measurement in lieu of a radium-226 and/or uranium measurement, the gross alpha particle activity 

analytical result will be used to determine the future monitoring frequency for radium-226 and/or 

uranium. If the gross alpha particle activity result is less than detection,1/2the detection limit will be used 

to determine compliance and the future monitoring frequency. 

(b) Monitoring and compliance requirements for beta particle and photon radioactivity. To determine 

compliance with the maximum contaminant levels in §141.66(d) for beta particle and photon 

radioactivity, a system must monitor at a frequency as follows: 

(1) Community water systems (both surface and ground water) designated by the State as vulnerable 

must sample for beta particle and photon radioactivity. Systems must collect quarterly samples for beta 

emitters and annual samples for tritium and strontium-90 at each entry point to the distribution system 

(hereafter called a sampling point), beginning within one quarter after being notified by the State. 

Systems already designated by the State must continue to sample until the State reviews and either 

reaffirms or removes the designation. 

(i) If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity at a 

sampling point has a running annual average (computed quarterly) less than or equal to 50 pCi/L 

(screening level), the State may reduce the frequency of monitoring at that sampling point to once every 

3 years. Systems must collect all samples required in paragraph (b)(1) of this section during the reduced 

monitoring period. 

(ii) For systems in the vicinity of a nuclear facility, the State may allow the CWS to utilize environmental 

surveillance data collected by the nuclear facility in lieu of monitoring at the system's entry point(s), 

where the State determines if such data is applicable to a particular water system. In the event that there 

is a release from a nuclear facility, systems which are using surveillance data must begin monitoring at 

the community water system's entry point(s) in accordance with paragraph (b)(1) of this section. 

(2) Community water systems (both surface and ground water) designated by the State as utilizing 

waters contaminated by effluents from nuclear facilities must sample for beta particle and photon 

radioactivity. Systems must collect quarterly samples for beta emitters and iodine-131 and annual 

samples for tritium and strontium-90 at each entry point to the distribution system (hereafter called a 

sampling point), beginning within one quarter after being notified by the State. Systems already 

designated by the State as systems using waters contaminated by effluents from nuclear facilities must 

continue to sample until the State reviews and either reaffirms or removes the designation. 

(i) Quarterly monitoring for gross beta particle activity shall be based on the analysis of monthly samples 

or the analysis of a composite of three monthly samples. The former is recommended. 

(ii) For iodine-131, a composite of five consecutive daily samples shall be analyzed once each quarter. 

As ordered by the State, more frequent monitoring shall be conducted when iodine-131 is identified in 

the finished water. 

(iii) Annual monitoring for strontium-90 and tritium shall be conducted by means of the analysis of a 

composite of four consecutive quarterly samples or analysis of four quarterly samples. The latter 

procedure is recommended. 

(iv) If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity at a 

sampling point has a running annual average (computed quarterly) less than or equal to 15 pCi/L 

(screening level), the State may reduce the frequency of monitoring at that sampling point to every 3 

years. Systems must collect the same type of samples required in paragraph (b)(2) of this section during 

the reduced monitoring period. 

(v) For systems in the vicinity of a nuclear facility, the State may allow the CWS to utilize environmental 

surveillance data collected by the nuclear facility in lieu of monitoring at the system's entry point(s), 

where the State determines if such data is applicable to a particular water system. In the event that there 

is a release from a nuclear facility, systems which are using surveillance data must begin monitoring at 

the community water system's entry point(s) in accordance with paragraph (b)(2) of this section. 

(3) Community water systems designated by the State to monitor for beta particle and photon 

radioactivity can not apply to the State for a waiver from the monitoring frequencies specified in 

paragraph (b)(1) or (b)(2) of this section. 

(4) Community water systems may analyze for naturally occurring potassium-40 beta particle activity 

from the same or equivalent sample used for the gross beta particle activity analysis. Systems are 

allowed to subtract the potassium-40 beta particle activity value from the total gross beta particle activity 

value to determine if the screening level is exceeded. The potassium-40 beta particle activity must be 

calculated by multiplying elemental potassium concentrations (in mg/L) by a factor of 0.82. 

(5) If the gross beta particle activity minus the naturally occurring potassium-40 beta particle activity 

exceeds the appropriate screening level, an analysis of the sample must be performed to identify the 

major radioactive constituents present in the sample and the appropriate doses must be calculated and 

summed to determine compliance with §141.66(d)(1), using the formula in §141.66(d)(2). Doses must 

also be calculated and combined for measured levels of tritium and strontium to determine compliance. 

(6) Systems must monitor monthly at the sampling point(s) which exceed the maximum contaminant 

level in §141.66(d) beginning the month after the exceedance occurs. Systems must continue monthly 

monitoring until the system has established, by a rolling average of 3 monthly samples, that the MCL is 

being met. Systems who establish that the MCL is being met must return to quarterly monitoring until 

they meet the requirements set forth in paragraph (b)(1)(i) or (b)(2)(iv) of this section. 

(c) General monitoring and compliance requirements for radionuclides. (1) The State may require more 

frequent monitoring than specified in paragraphs (a) and (b) of this section, or may require confirmation 

samples at its discretion. The results of the initial and confirmation samples will be averaged for use in 

compliance determinations. 

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(2) Each public water systems shall monitor at the time designated by the State during each compliance 

period. 

(3) Compliance: Compliance with §141.66 (b) through (e) will be determined based on the analytical 

result(s) obtained at each sampling point. If one sampling point is in violation of an MCL, the system is in 

violation of the MCL. 

(i) For systems monitoring more than once per year, compliance with the MCL is determined by a 

running annual average at each sampling point. If the average of any sampling point is greater than the 

MCL, then the system is out of compliance with the MCL. 

(ii) For systems monitoring more than once per year, if any sample result will cause the running average 

to exceed the MCL at any sample point, the system is out of compliance with the MCL immediately. 

(iii) Systems must include all samples taken and analyzed under the provisions of this section in 

determining compliance, even if that number is greater than the minimum required. 

(iv) If a system does not collect all required samples when compliance is based on a running annual 

average of quarterly samples, compliance will be based on the running average of the samples 

collected. 

(v) If a sample result is less than the detection limit, zero will be used to calculate the annual average, 

unless a gross alpha particle activity is being used in lieu of radium-226 and/or uranium. If the gross 

alpha particle activity result is less than detection,1/2the detection limit will be used to calculate the 

annual average. 

(4) States have the discretion to delete results of obvious sampling or analytic errors. 

(5) If the MCL for radioactivity set forth in §141.66 (b) through (e) is exceeded, the operator of a 

community water system must give notice to the State pursuant to §141.31 and to the public as required 

by subpart Q of this part. 

[65 FR 76745, Dec. 7, 2000, as amended at 69 FR 38855, June 29, 2004] 

§ 141.27 Alternate analytical techniques. 

 top

(a) With the written permission of the State, concurred in by the Administrator of the U.S. EPA, an 

alternate analytical technique may be employed. An alternate technique shall be accepted only if it is 

substantially equivalent to the prescribed test in both precision and accuracy as it relates to the 

determination of compliance with any MCL. The use of the alternate analytical technique shall not 

decrease the frequency of monitoring required by this part. 

[45 FR 57345, Aug. 27, 1980] 

§ 141.28 Certified laboratories. 

 top

(a) For the purpose of determining compliance with §141.21 through 141.27, 141.30, 141.40, 141.74, 

141.89 and 141.402, samples may be considered only if they have been analyzed by a laboratory 

certified by the State except that measurements of alkalinity, calcium, conductivity, disinfectant residual, 

orthophosphate, pH, silica, temperature and turbidity may be performed by any person acceptable to the 

State. 

(b) Nothing in this part shall be construed to preclude the State or any duly designated representative of 

the State from taking samples or from using the results from such samples to determine compliance by a 

supplier of water with the applicable requirements of this part. 

[45 FR 57345, Aug. 27, 1980; 47 FR 10999, Mar. 12, 1982, as amended at 59 FR 34323, July 1, 1994; 

64 FR 67465, Dec. 1, 1999; 71 FR 65651, Nov. 8, 2006] 

§ 141.29 Monitoring of consecutive public water systems. 

 top

When a public water system supplies water to one or more other public water systems, the State may 

modify the monitoring requirements imposed by this part to the extent that the interconnection of the 

systems justifies treating them as a single system for monitoring purposes. Any modified monitoring 

shall be conducted pursuant to a schedule specified by the State and concurred in by the Administrator 

of the U.S. Environmental Protection Agency. 

Appendix A to Subpart C of Part 141—Alternative Testing Methods Approved for 

Analyses Under the Safe Drinking Water Act 

 top

Only the editions stated in the following table are approved. 

Alternative Testing Methods for Contaminants Listed at 40 CFR 141.21(f)(3) 

Organism Methodology

SM 21st 

edition1 Other

Total 

Coliforms

Total Coliform Fermentation 

Technique

9221 A, B

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Alternative Testing Methods for Contaminants Listed at 40 CFR 141.21(f)(6) 

Alternative Testing Methods for Contaminants Listed at 40 CFR 141.23(k)(1) 

 Total Coliform Membrane 

Filter Technique

9222 A, B, C

 Presence-Absence (P–A) 

Coliform Test

9221 D

 ONPG–MUG Test 9223

 ColitagTM Modified 

ColitagTM13

Organism Methodology

SM 

20th 

edition6

SM 

21st 

edition1

SM 

online3 Other

E. coli ONPG–MUG 

Test

9223 B 9223 B 9223 B–

97

 Modified 

ColitagTM13

Contaminant Methodology

EPA 

method

SM 

21st 

edition1

SM 

online3 ASTM4 Other

Alkalinity Titrimetric 2320 B D 

1067–

06 B

Antimony Hydride—Atomic Absorption D 

3697–

07

 Atomic Absorption; Furnace 3113 B 3113 

B–04

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Arsenic Atomic Absorption; Furnace 3113 B 3113 

B–04

D 

2972–

08 C

 Hydride Atomic Absorption 3114 B 3114 

B–09

D 

2972–

08 B

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Barium Inductively Coupled Plasma 3120 B

 Atomic Absorption; Direct 3111 D

 Atomic Absorption; Furnace 3113 B 3113 

B–04

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Beryllium Inductively Coupled Plasma 3120 B

 Atomic Absorption; Furnace 3113 B 3113 

B–04

D 

3645–

08 B

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Cadmium Atomic Absorption; Furnace 3113 B 3113 

B–04

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Calcium EDTA titrimetric 3500–

Ca B

D 511–

09 A

 Atomic Absorption; Direct Aspiration 3111 B D 511–

09 B

 Inductively Coupled Plasma 3120 B

 Axially viewed inductively coupled 200.5, 

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plasma-atomic emission spectrometry 

(AVICP–AES)

Revision 

4.2.2

 Ion Chromatography D 

6919–

09

Chromium Inductively Coupled Plasma 3120 B

 Atomic Absorption; Furnace 3113 B 3113 

B–04

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Copper Atomic Absorption; Furnace 3113 B 3113 

B–04

D 

1688–

07 C

 Atomic Absorption; Direct Aspiration 3111 B D 

1688–

07 A

 Inductively Coupled Plasma 3120 B

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Conductivity Conductance 2510 B

Cyanide Manual Distillation followed by D2036–

06 A

 Spectrophotometric, Amenable 4500–

CN−G

D2036–

06 B

 Spectrophotometric Manual 4500–

CN−E

D2036–

06 A

 Selective Electrode 4500–

CN−F

 Gas 

Chromatography/Mass Spectrometry 

Headspace

ME355.017

Fluoride Ion Chromatography 4110 B

 Manual Distillation; Colorimetric 

SPADNS

4500–FB, D

 Manual Electrode 4500–

F–C

D 

1179–

04 B

 Automated Alizarin 4500–

F–E

 Arsenite-Free Colorimetric SPADNS Hach SPADNS 2 

Method 10225.22

Lead Atomic Absorption; Furnace 3113 B 3113 

B–04

D 

3559–

08 D

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Magnesium Atomic Absorption; Direct 3111 B D 511–

09 B

 Inductively Coupled Plasma 3120 B

 Complexation Titrimetric Methods 3500–

Mg B

D 511–

09 A

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.22

 Ion Chromatography D 

6919–

09

Mercury Manual, Cold Vapor 3112 B

Nickel Inductively Coupled Plasma 3120 B

 Atomic Absorption; Direct 3111 B

 Atomic Absorption; Furnace 3113 B 3113 

B–04

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

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Alternative Testing Methods for Contaminants Listed at 40 CFR 141.24(e)(1) 

Nitrate Ion Chromatography 4110 B

 Automated Cadmium Reduction 4500–

NO3–F

 Manual Cadmium Reduction 4500–

NO3–E

 Ion Selective Electrode 4500–

NO3–D

 Reduction/Colorimetric Systea Easy (1–

Reagent).8

 Colorimetric; Direct Hach 

TNTplusTM835/836 

Method 10206.23

Nitrite Ion Chromatography 4110 B

 Automated Cadmium Reduction 4500–

NO3

−F

 Manual Cadmium Reduction 4500–

NO3

−E

 Spectrophotometric 4500–

NO2

−B

 Reduction/Colorimetric Systea Easy 

(1-Reagent)8

Orthophosphate Ion Chromatography 4110 B

 Colorimetric, ascorbic acid, single 

reagent

4500–P 

E

4500–

P E–99

 Colorimetric, Automated, Ascorbic Acid 4500–P 

F

4500–

P F–99

pH Electrometric 4500–

H+B

Selenium Hydride—Atomic Absorption 3114 B 3114 

B–09

D 

3859–

08 A

 Atomic Absorption; Furnace 3113 B 3113 

B–04

D 

3859–

08 B

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

Silica Colorimetric D859–

05

 Molybdosilicate 4500–

SiO2C

 Heteropoly blue 4500–

SiO2D

 Automated for Molybdate-reactive Silica 4500–

SiO2E

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

 Inductively Coupled Plasma 3120 B

Sodium Atomic Absorption; Direct Aspiration 3111 B

 Axially viewed inductively coupled 

plasma-atomic emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.22

 Ion Chromatography D 

6919–

09

Temperature Thermometric 2550

Contaminant Methodology

EPA 

method

SM 

21st 

edition1

SM 

online3

Benzene Purge & Trap/Gas 524.39

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Chromatography/Mass 

Spectrometry

Carbon tetrachloride Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Chlorobenzene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,2-Dichlorobenzene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,4-Dichlorobenzene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,2-Dichloroethane Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

cis-Dichloroethylene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

TransDichloroethylenePurge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Dichloromethane Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,2-Dichloropropane Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Ethylbenzene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Styrene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Tetrachloroethylene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,1,1-Trichloroethane Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Trichloroethylene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Toluene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,2,4-

Trichlorobenzene

Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,1-Dichloroethylene Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

1,1,2-Trichlorethane Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Vinyl chloride Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Xylenes (total) Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

2,4-D Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

2,4,5-TP (Silvex) Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

Carbofuran High-performance liquid 

chromatography (HPLC) 

 6610 B 6610 

B–04

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Alternative Testing Methods for Contaminants Listed at 40 CFR 141.25(a) 

with post-column 

derivatization and 

fluorescence detection

Dalapon Ion Chromatography 

Electrospray Ionization 

Tandem Mass 

Spectrometry (IC–ESI–

MS/MS)

55714

 Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

Dibromochloropropane 

(DBCP)

Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Dinoseb Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

Ethyl dibromide (EDB) Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Glyphosate High-Performance Liquid 

Chromatography (HPLC) 

with Post-Column 

Derivatization and 

Fluorescence Detection

6651 B 6651 

B–00

Oxamyl High-performance liquid 

chromatography (HPLC) 

with post-column 

derivatization and 

fluorescence detection

 6610 B 6610 

B–04

Pentachlorophenol Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

Picloram Gas 

Chromatography/Electron 

Capture Detection 

(GC/ECD)

6640 B 6640 

B–01

Total Trihalomethanes Purge & Trap/Gas 

Chromatography/Mass 

Spectrometry

524.3

Contaminant Methodology

SM 21st

edition1 ASTM4

Naturally Occurring:

Gross alpha and beta Evaporation 7110 B

Gross alpha Coprecipitation 7110 C

Radium 226 Radon emanation 7500–Ra 

C

D3454–

05

 Radiochemical 7500–Ra 

B

D2460–

07

Radium 228 Radiochemical 7500–Ra 

D

Uranium Radiochemical 7500–U B

 ICP–MS D5673–

05

 Alpha spectrometry 7500–U C D3972–

09

 Laser Phosphorimetry D5174–

07

Man-Made:

Radioactive Cesium Radiochemical 7500–Cs 

B

 Gamma Ray 

Spectrometry

7120 D3649–

06

Radioactive Iodine Radiochemical 7500–I B D3649–

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Alternative Testing Methods for Contaminants Listed at 40 CFR 141.74(a)(1) 

Alternative Testing Methods for Disinfectant Residuals Listed at 40 CFR 141.74(a)(2) 

06

 7500–I C

 7500–I D

 Gamma Ray 

Spectrometry

7120 D4785–

08

Radioactive Strontium 

89, 90

Radiochemical 7500–Sr 

B

Tritium Liquid Scintillation 7500−3H 

B

D4107–

08

Gamma Emitters Gamma Ray 

Spectrometry

7120 D3649–

06

 7500–Cs 

B

D4785–

08

 7500–I B

Organism Methodology

SM 21st

edition1 Other

Total Coliform Total Coliform Fermentation 

Technique

9221 A, B, 

C

 Total Coliform Membrane Filter 

Technique

9222 A, B, 

C

 ONPG–MUG Test 9223

Fecal Coliforms Fecal Coliform Procedure 9221 E

 Fecal Coliform Filter 

Procedure

9222 D

Heterotrophic 

bacteria

Pour Plate Method 9215 B

Turbidity Nephelometric Method 2130 B

 Laser Nephelometry (on-line) Mitchell 

M527110

 LED Nephelometry (on-line) Mitchell 

M533111

 LED Nephelometry (on-line) AMI 

Turbiwell15

 LED Nephelometry (portable) Orion 

AQ450012

Residual Methodology

SM 21st 

Edition1 ASTM4 Other

Free 

Chlorine

Amperometric Titration 4500–Cl D D 1253–

08

 DPD Ferrous Titrimetric 4500–Cl F

 DPD Colorimetric 4500–Cl G

 Syringaldazine (FACTS) 4500–Cl H

 On-line Chlorine Analyzer EPA 334.0.16

 Amperometric Sensor ChloroSense.17

Total 

Chlorine

Amperometric Titration 4500–Cl D D 1253–

08

 Amperometric Titration 

(Low level measurement)

4500–Cl E

 DPD Ferrous Titrimetric 4500–Cl F

 DPD Colorimetric 4500–Cl G

 Iodometric Electrode 4500–Cl I

 On-line Chlorine Analyzer EPA 334.0.16

 Amperometric Sensor ChloroSense.17

Chlorine 

Dioxide

Amperometric Titration 4500–

ClO2C

 Amperometric Titration 4500–

ClO2E

Ozone Indigo Method 4500–O3B

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Alternative Testing Methods for Contaminants Listed at 40 CFR 141.131(b)(1) 

Alternative Testing Methods for Disinfectant Residuals Listed at 40 CFR 141.131(c)(1) 

Alternative Testing Methods for Disinfectant Residuals Listed at 40 CFR 141.131(c)(2), If 

Contaminant Methodology

EPA 

Method ASTM4

SM 21st 

Edition1

TTHM P&T/GC/MS 9524.3

HAA5 LLE (diazomethane)/GC/ECD 6251 B.

 Ion Chromatography 

Electrospray Ionization 

Tandem Mass Spectrometry 

(IC–ESI–MS/MS)

14557

Bromate Two-Dimensional Ion 

Chromatography (IC)

18302.0

 Ion Chromatography 

Electrospray Ionization 

Tandem Mass Spectrometry 

(IC–ESI–MS/MS)

14557

 Chemically Suppressed Ion 

Chromatography

D 

6581–

08 A.

 Electrolytically Suppressed 

Ion Chromatography

D 

6581–

08 B.

Chlorite Chemically Suppressed Ion 

Chromatography

D 

6581–

08 A.

 Electrolytically Suppressed 

Ion Chromatography

D 

6581–

08 B.

Chlorite—daily 

monitoring as 

prescribed in 40 

CFR 141.132(b)

(2)(i)(A).

Amperometric Titration 4500–

ClO2E.

Residual Methodology

SM 21st 

Edition1 ASTM4 Other

Free Chlorine Amperometric Titration 4500–Cl D D 1253–

08

 DPD Ferrous 

Titrimetric

4500–Cl F

 DPD Colorimetric 4500–Cl G

 Syringaldazine 

(FACTS)

4500–Cl H

 Amperometric Sensor ChloroSense.17

 On-line Chlorine 

Analyzer

EPA 334.0.16

Combined 

Chlorine

Amperometric Titration 4500–Cl D D 1253–

08

 DPD Ferrous 

Titrimetric

4500–Cl F

 DPD Colorimetric 4500–Cl G

Total Chlorine Amperometric Titration 4500–Cl D D 1253–

08

 Low level 

Amperometric Titration

4500–Cl E

 DPD Ferrous 

Titrimetric

4500–Cl F

 DPD Colorimetric 4500–Cl G

 Iodometric Electrode 4500–Cl I

 Amperometric Sensor ChloroSense.17

 On-line Chlorine 

Analyzer

EPA 334.0.16

Chlorine 

Dioxide

Amperometric Method 

II

4500–

ClO2E.

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Approved by the State 

Alternative Testing Methods for Parameters Listed at 40 CFR 141.131(d) 

Alternative Testing Methods With MRL ≤ 0.0010 mg/L for Monitoring Listed at 40 CFR 141.132(b)

(3)(ii)(B) 

Alternative Testing Methods for Contaminants Listed at 40 CFR 141.402(c)(2) 

Alternative Testing Methods for Contaminants Listed at 40 CFR 141.704(b) 

Alternative Testing Methods for Contaminants Listed at 40 CFR 143.4(b) 

Residual Methodology Method

Free Chlorine Test Strips Method D99–0035

Parameter Methodology

SM 

21st 

edition1 EPA

Total Organic Carbon (TOC) High Temperature 

Combustion

5310 B 415.3, 

Rev 

1.219

 Persulfate-Ultraviolet or 

Heated Persulfate Oxidation

5310 C 415.3, 

Rev 1.2

 Wet Oxidation 5310 D 415.3, 

Rev 1.2

Specific Ultraviolet 

Absorbance (SUVA)

Calculation using DOC and 

UV254data

415.3, 

Rev 1.2

Dissolved Organic 

Carbon (DOC)

High Temperature 

Combustion

5310 B 415.3, 

Rev 1.2

 Persulfate-Ultraviolet or 

Heated Persulfate Oxidation

5310 C 415.3, 

Rev 1.2

 Wet Oxidation 5310 D 415.3, 

Rev 1.2

Ultraviolet 

absorption at 254 

nm (UV254)

Spectrophotometry 5910 B 415.3, 

Rev 1.2

Contaminant Methodology

EPA 

method

Bromate Two-Dimensional Ion Chromatography (IC) 302.018

 Ion Chromatography Electrospray Ionization 

Tandem Mass Spectrometry (IC–ESI–MS/MS)

55714

Organism Methodology

SM 20th 

edition6

SM 21st 

edition1

SM 

online3 Other

E. coli Colilert 9223 B 9223 B–

97

 Colisure 9223 B 9223 B–

97

 Colilert-18 9223 B 9223 B 9223 B–

97

 Readycult® Readycult®.

20

 Colitag Modified 

ColitagTM.

13

 Chromocult® Chromocult®.

21

Enterococci Multiple-Tube 

Technique

9230 B–

04

Organism Methodology SM 20th edition6

E. coli Membrane Filtration, Two Step 9222 D/9222 G

Contaminant Methodology

EPA 

method ASTM4

SM 21st

edition1

SM 

online3

Aluminum Axially viewed 

inductively coupled 

200.5, 

Revision 

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plasma-atomic 

emission spectrometry 

(AVICP–AES)

4.2.2

 Atomic Absorption; 

Direct

3111D

 Atomic Absorption; 

Furnace

3113 B 3113 B–

04

 Inductively Coupled 

Plasma

3120 B

Chloride Silver Nitrate Titration D 512–

04 B

4500–

Cl−B

 Ion Chromatography 4110 B

 Potentiometric Titration 4500–

Cl−D

Color Visual Comparison 2120 B

Foaming 

Agents

Methylene Blue Active 

Substances (MBAS)

5540 C

Iron Axially viewed 

inductively coupled 

plasma-atomic 

emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.22

 Atomic Absorption; 

Direct

3111 B

 Atomic Absorption; 

Furnace

3113 B 3113 B–

04

 Inductively Coupled 

Plasma

3120 B

Manganese Axially viewed 

inductively coupled 

plasma-atomic 

emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

 Atomic Absorption; 

Direct

3111 B

 Atomic Absorption; 

Furnace

3113 B 3113 B–

04

 Inductively Coupled 

Plasma

3120 B

Odor Threshold Odor Test 2150 B

Silver Axially viewed 

inductively coupled 

plasma-atomic 

emission spectrometry 

(AVICP–AES)

200.5, 

Revision 

4.2.2

 Atomic Absorption; 

Direct

3111 B

 Atomic Absorption; 

Furnace

3113 B 3113 B–

04

 Inductively Coupled 

Plasma

3120 B

Sulfate Ion Chromatography 4110 B

 Gravimetric with 

ignition of residue

4500–

SO4

−2C

4500–

SO4

−2C–

97

 Gravimetric with drying 

of residue

4500–

SO4

−2D

4500–

SO4

−2D–

97

 Turbidimetric method D 516–

07

4500–

SO4

−2E

4500–

SO4

−2E–

97

 Automated 

methylthymol blue 

method

4500–

SO4

−2F

4500–

SO4

−2F–

97

Total 

Dissolved 

Solids

Total Dissolved Solids 

Dried at 180 deg C

2540 C

Zinc Axially viewed 200.5, 

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1 Standard Methods for the Examination of Water and Wastewater , 21st edition (2005). 

Available from American Public Health Association, 800 I Street, NW., Washington, DC 

20001–3710. 

2 EPA Method 200.5, Revision 4.2. “Determination of Trace Elements in Drinking Water by 

Axially Viewed Inductively Coupled Plasma-Atomic Emission Spectrometry.” 2003. 

EPA/600/R–06/115. (Available at http://www.epa.gov/nerlcwww/ordmeth.htm .) 

3 Standard Methods Online are available at http://www.standardmethods.org . The year in 

which each method was approved by the Standard Methods Committee is designated by the 

last two digits in the method number. The methods listed are the only online versions that may 

be used. 

4 Available from ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428–

2959 or http://astm.org . The methods listed are the only alternative versions that may be 

used. 

5 Method D99–003, Revision 3.0. “Free Chlorine Species (HOCl−and OCl−) by Test Strip,” 

November 21, 2003. Available from Industrial Test Systems, Inc., 1875 Langston St., Rock 

Hill, SC 29730. 

6 Standard Methods for the Examination of Water and Wastewater , 20th edition (1998). 

Available from American Public Health Association, 800 I Street, NW., Washington, DC 

20001–3710. 

7 Method ME355.01, Revision 1.0. “Determination of Cyanide in Drinking Water by GC/MS 

Headspace,” May 26, 2009. Available at http://www.nemi.gov or from James Eaton, H & E 

Testing Laboratory, 221 State Street, Augusta, ME 04333. (207) 287–2727. 

8 Systea Easy (1-Reagent). “Systea Easy (1-Reagent) Nitrate Method,” February 4, 2009. 

Available at http://www.nemi.gov or from Systea Scientific, LLC., 900 Jorie Blvd., Suite 35, 

Oak Brook, IL 60523. 

9 EPA Method 524.3, Version 1.0. “Measurement of Purgeable Organic Compounds in Water 

by Capillary Column Gas Chromatography/Mass Spectrometry,” June 2009. EPA 815–B–09–

009. Available at http://epa.gov/safewater/methods/analyticalmethods_ogwdw.html . 

10 Mitchell Method M5271, Revision 1.1. “Determination of Turbidity by Laser Nephelometry,” 

March 5, 2009. Available at http://www.nemi.gov or from Leck Mitchell, PhD, PE, 656 

Independence Valley Dr., Grand Junction, CO 81507. 

11 Mitchell Method M5331, Revision 1.1. “Determination of Turbidity by LED Nephelometry,” 

March 5, 2009. Available at http://www.nemi.gov or from Leck Mitchell, PhD, PE, 656 

Independence Valley Dr., Grand Junction, CO 81507. 

12 Orion Method AQ4500, Revision 1.0. “Determination of Turbidity by LED Nephelometry,” 

May 8, 2009. Available at http://www.nemi.gov or from Thermo Scientific, 166 Cummings 

Center, Beverly, MA 01915, http://www.thermo.com . 

13 Modified ColitagTM Method, “Modified ColitagTM Test Method for the Simultaneous 

Detection of E. coli and other Total Coliforms in Water (ATP D05–0035),” August 28, 2009. 

Available at http://www.nemi.gov or from CPI, International, 580 Skylane Boulevard, Santa 

Rosa, CA 95403. 

14 EPA Method 557. “Determination of Haloacetic Acids, Bromate, and Dalapon in Drinking 

Water by Ion Chromatography Electrospray Ionization Tandem Mass Spectrometry (IC–ESI–

MS/MS),” September 2009. EPA 815–B–09–012. Available at 

http://water.epa.gov/scitech/drinkingwater/labcert/analyticalmethods_expedited.cfm. 

15 AMI Turbiwell, “Continuous Measurement of Turbidity Using a SWAN AMI Turbiwell 

Turbidimeter,” August 2009. Available at http://www.nemi.gov or from Markus Bernasconi, 

SWAN Analytische Instrumente AG, Studbachstrasse 13, CH–8340 Hinwil, Switzerland. 

16 EPA Method 334.0. “Determination of Residual Chlorine in Drinking Water Using an On-line 

Chlorine Analyzer,” August 2009. EPA 815–B–09–013. Available at 

http://epa.gov/safewater/methods/analyticalmethods_ogwdw.html . 

17 ChloroSense. “Measurement of Free and Total Chlorine in Drinking Water by Palintest 

ChloroSense,” September 2009. Available at http://www.nemi.gov or from Palintest Ltd, 21 

Kenton Lands Road, PO Box 18395, Erlanger, KY 41018. 

18 EPA Method 302.0. “Determination of Bromate in Drinking Waters using Two-Dimensional 

inductively coupled 

plasma-atomic 

emission spectrometry 

(AVICP–AES)

Revision 

4.2

 Atomic Absorption; 

Direct Aspiration

3111 B

 Inductively Coupled 

Plasma

3120 B

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Ion Chromatography with Suppressed Conductivity Detection,” September 2009. EPA 815–B–

09–014. Available at http://epa.gov/safewater/methods/analyticalmethods_ogwdw.html . 

19 EPA 415.3, Revision 1.2. “Determination of Total Organic Carbon and Specific UV 

Absorbance at 254 nm in Source Water and Drinking Water,” August 2009. EPA/600/R–

09/122. Available at http://www.epa.gov/nerlcwww/ordmeth.htm. 

20 Readycult®Method, “Readycult®Coliforms 100 Presence/Absence Test for Detection and 

Identification of Coliform Bacteria and Escherichia coli in Finished Waters,” January, 2007. 

Version 1.1. Available from EMD Chemicals (affiliate of Merck KGaA, Darmstadt, Germany), 

480 S. Democrat Road, Gibbstown, NJ 08027–1297. 

21 Chromocult®Method, “Chromocult®Coliform Agar Presence/Absence Membrane Filter Test 

Method for Detection and Identification of Coliform Bacteria and Escherichia coli in Finished 

Waters,” November, 2000. Version 1.0. EMD Chemicals (affiliate of Merck KGaA, Darmstadt, 

Germany), 480 S. Democrat Road, Gibbstown, NJ 08027–1297. 

22 Hach Company Method, “Hach Company SPADNS 2 (Arsenic-free) Fluoride Method 

10225—Spectrophotometric Measurement of Fluoride in Water and Wastewater,” January 

2011. 5600 Lindbergh Drive, P.O. Box 389, Loveland, Colorado 80539. (Available at 

http://www.hach.com. ) 

23 Hach Company Method, “Hach Company TNTplusTM 835/836 Nitrate Method 10206—

Spectrophotometric Measurement of Nitrate in Water and Wastewater,” January 2011. 5600 

Lindbergh Drive, P.O. Box 389, Loveland, Colorado 80539. (Available at 

http://www.hach.com. ) 

[74 FR 38353, Aug. 3, 2009, as amended at 74 FR 57914, Nov. 10, 2009; 74 FR 63069, Dec. 2, 2009; 

75 FR 32299, June 8, 2010; 76 FR 37018, June 24, 2011] 

Subpart D—Reporting and Recordkeeping 

 top

§ 141.31 Reporting requirements. 

 top

(a) Except where a shorter period is specified in this part, the supplier of water shall report to the State 

the results of any test measurement or analysis required by this part within (1) The first ten days 

following the month in which the result is received, or (2) the first ten days following the end of the 

required monitoring period as stipulated by the State, whichever of these is shortest. 

(b) Except where a different reporting period is specified in this part, the supplier of water must report to 

the State within 48 hours the failure to comply with any national primary drinking water regulation 

(including failure to comply with monitoring requirements) set forth in this part. 

(c) The supplier of water is not required to report analytical results to the State in cases where a State 

laboratory performs the analysis and reports the results to the State office which would normally receive 

such notification from the supplier. 

(d) The public water system, within 10 days of completing the public notification requirements under 

Subpart Q of this part for the initial public notice and any repeat notices, must submit to the primacy 

agency a certification that it has fully complied with the public notification regulations. The public water 

system must include with this certification a representative copy of each type of notice distributed, 

published, posted, and made available to the persons served by the system and to the media. 

(e) The water supply system shall submit to the State within the time stated in the request copies of any 

records required to be maintained under §141.33 hereof or copies of any documents then in existence 

which the State or the Administrator is entitled to inspect pursuant to the authority of section 1445 of the 

Safe Drinking Water Act or the equivalent provisions of State law. 

[40 FR 59570, Dec. 24, 1975, as amended at 45 FR 57345, Aug. 27, 1980; 65 FR 26022, May 4, 2000] 

§ 141.32 [Reserved] 

 top

§ 141.33 Record maintenance. 

 top

Any owner or operator of a public water system subject to the provisions of this part shall retain on its 

premises or at a convenient location near its premises the following records: 

(a) Records of microbiological analyses and turbidity analyses made pursuant to this part shall be kept 

for not less than 5 years. Records of chemical analyses made pursuant to this part shall be kept for not 

less than 10 years. Actual laboratory reports may be kept, or data may be transferred to tabular 

summaries, provided that the following information is included: 

(1) The date, place, and time of sampling, and the name of the person who collected the sample; 

(2) Identification of the sample as to whether it was a routine distribution system sample, check sample, 

raw or process water sample or other special purpose sample; 

(3) Date of analysis; 

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(4) Laboratory and person responsible for performing analysis; 

(5) The analytical technique/method used; and 

(6) The results of the analysis. 

(b) Records of action taken by the system to correct violations of primary drinking water regulations shall 

be kept for a period not less than 3 years after the last action taken with respect to the particular 

violation involved. 

(c) Copies of any written reports, summaries or communications relating to sanitary surveys of the 

system conducted by the system itself, by a private consultant, or by any local, State or Federal agency, 

shall be kept for a period not less than 10 years after completion of the sanitary survey involved. 

(d) Records concerning a variance or exemption granted to the system shall be kept for a period ending 

not less than 5 years following the expiration of such variance or exemption. 

(e) Copies of public notices issued pursuant to Subpart Q of this part and certifications made to the 

primacy agency pursuant to §141.31 must be kept for three years after issuance. 

(f) Copies of monitoring plans developed pursuant to this part shall be kept for the same period of time 

as the records of analyses taken under the plan are required to be kept under paragraph (a) of this 

section, except as specified elsewhere in this part. 

[40 FR 59570, Dec. 24, 1975, as amended at 65 FR 26022, May 4, 2000; 71 FR 478, Jan. 4, 2006] 

§ 141.34 [Reserved] 

 top

§ 141.35 Reporting for unregulated contaminant monitoring results. 

 top

(a) General applicability. This section applies to any owner or operator of a public water system (PWS) 

required to monitor for unregulated contaminants under §141.40(a); such owner or operator is referred 

to as “you.” This section specifies the information that must be reported to EPA prior to the 

commencement of monitoring and describes the process for reporting monitoring results to EPA. For the 

purposes of this section, PWS “population served” includes the sum of the retail population served 

directly by the PWS plus the population served by any consecutive system(s) receiving all or part of its 

finished water from that PWS. For purposes of this section, the term “finished” means water that is 

introduced into the distribution system of a PWS and is intended for distribution and consumption without 

further treatment, except the treatment necessary to maintain water quality in the distribution system 

(e.g., booster disinfection, addition of corrosion control chemicals). For purposes of this section, the term 

“State” refers to the State or Tribal government entity that has jurisdiction over your PWS even if that 

government does not have primary enforcement responsibility for PWSs under the Safe Drinking Water 

Act. For purposes of this section, the term “PWS Official” refers to the person at your PWS who is able 

to function as the official spokesperson for the system's Unregulated Contaminant Monitoring Regulation 

(UCMR) activities; and the term “PWS Technical Contact” refers to the person at your PWS who is 

responsible for the technical aspects of your UCMR activities, such as details concerning sampling and 

reporting. 

(b) Reporting by all systems . You must meet the reporting requirements of this paragraph if you meet 

the applicability criteria in §141.40(a)(2). 

(1) Where to submit UCMR reporting requirement information . Some of your reporting requirements are 

to be fulfilled electronically, and others by mail. Information that must be submitted using EPA's 

electronic data reporting system must be submitted through: 

http://www.epa.gov/safewater/ucmr/ucmr2/reporting.html . Documentation that is required to be mailed 

can be submitted either: To UCMR Sampling Coordinator, USEPA, Technical Support Center, 26 West 

Martin Luther King Drive (MS 140), Cincinnati, OH 45268; or by e-mail at 

UCMR_Sampling_Coordinator@epa.gov ; or by fax at (513) 569–7191. In addition, you must notify the 

public of the availability of unregulated contaminant monitoring data as provided in Subpart Q (Public 

Notification) of this part (40 CFR 141.207). Community Water Systems that detect unregulated 

contaminants under this monitoring must also address such detections as part of their Consumer 

Confidence Reports, as provided in Subpart O of this part (40 CFR 141.151). 

(2) Contacting EPA if your system does not meet applicability criteria or has a status change. If you have 

received a letter from EPA concerning your required monitoring and your system does not meet the 

applicability criteria for UCMR established in §141.40(a)(2), or if a change occurs at your system that 

may affect your requirements under UCMR as defined in §141.40(a)(3) through (5), you must fax, mail, 

or e-mail a letter to EPA, as specified in paragraph (b)(1) of this section. The letter must be from your 

PWS Official and must include an explanation as to why the UCMR requirements are not applicable to 

your PWS, or have changed for your PWS, along with the appropriate contact information. EPA will 

make an applicability determination based on your letter and in consultation with the State when 

necessary. You are subject to UCMR requirements unless and until you receive a letter from EPA 

agreeing that you do not meet the applicability criteria. 

(c) Reporting by large systems . If you serve a population of more than 10,000 people, and meet the 

applicability criteria in §141.40(a)(2)(i), you must meet the reporting requirements in paragraphs (c)(1) 

through (8) of this section. 

(1) Contact information . You must provide contact information by April 4, 2007, and provide updates 

within 30 days if this information changes. The contact information must be submitted using EPA's 

electronic data reporting system, as specified in paragraph (b)(1) of this section, and include the name, 

affiliation, mailing address, phone number, fax number, and e-mail address for your PWS Technical 

Contact and your PWS Official. 

(2) Sampling location and inventory information. You must provide your sampling location and inventory 

information by August 2, 2007 using EPA's electronic data reporting system. You must submit the 

following information for each sampling location, or for each approved representative sampling location 

(as specified in paragraph (c)(3) of this section regarding representative sampling locations): PWS 

identification (PWSID) code; PWS facility identification code; water source type, sampling point 

identification code; and sampling point type code; ( as defined in Table 1, paragraph (e) of this section). 

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If this information changes, you must report updates to EPA's electronic data reporting system within 30 

days of the change. 

(3) Proposed ground water representative sampling locations . Some systems that use ground water as 

a source and have multiple entry points to the distribution system (EPTDSs) may propose monitoring at 

representative entry point(s), rather than monitor at every EPTDS, as follows: 

(i) Qualifications . Large PWSs that have EPA- or State-approved alternate EPTDS sampling locations 

from a previous UCMR cycle, or as provided for under §§141.23(a)(1), 141.24(f)(1), or 141.24(h)(1), may 

submit a copy of documentation from their State or EPA that approves their alternative sampling plan for 

EPTDSs. PWSs that do not have an approved alternative EPTDS sampling plan may submit a proposal 

to sample at representative EPTDS(s) rather than at each individual EPTDS if: They use ground water 

as a source; all of their well sources have either the same treatment or no treatment; and they have 

multiple EPTDSs from the same source, such as an aquifer. You must submit a copy of the existing 

alternate EPTDS sampling plan or your representative well proposal, as appropriate, by May 4, 2007, as 

specified in paragraph (b)(1) of this section. 

(ii) Demonstration. If you are submitting a proposal to sample at representative EPTDS(s) rather than at 

each individual EPTDS, you must demonstrate that any EPTDS that you select as representative of the 

ground water you supply from multiple wells is associated with a well that draws from the same aquifer 

as the wells it will represent. You must submit the following information for each proposed representative 

sampling location: PWSID Code, PWS Facility Identification Code, and Sampling Point Identification 

Code (as defined in Table 1, paragraph (e) of this section). You must also include documentation to 

support your proposal that the specified wells are representative of other wells. This documentation can 

include system-maintained well logs or construction drawings indicating that the representative well(s) 

is/are at a representative depth, and details of well casings and grouting; data demonstrating relative 

homogeneity of water quality constituents (e.g., pH, dissolved oxygen, conductivity, iron, manganese) in 

samples drawn from each well; and data showing that your wells are located in a limited geographic 

area (e.g., all wells within a 0.5 mile radius) and/or, if available, the hydrogeologic data indicating the 

time of travel separating the representative well from each of the individual wells it represents (e.g., all 

wells within a five-year time of travel delineation). Your proposal must be sent in writing to EPA, as 

specified in paragraph (b)(1) of this section. You must also provide a copy of this information to the 

State, unless otherwise directed by the State. Information about the actual or potential occurrence or 

non-occurrence of contaminants in an individual well, or a well's vulnerability to contamination, must not 

be used as a basis for selecting a representative well. 

(iii) Approval . EPA or the State (as specified in the Partnership Agreement reached between the State 

and EPA) will review your proposal, coordinate any necessary changes with you, and approve the final 

list of EPTDSs where you will be required to monitor. Your plan will not be final until you receive written 

approval from EPA or the State. 

(4) Contacting EPA if your PWS has not been notified of requirements. If you believe you are subject to 

UCMR requirements, as defined in §141.40(a)(1) and (2)(i), and you have not been notified by either 

EPA or your State by June 4, 2007, you must send a letter to EPA, as specified in paragraph (b)(1) of 

this section. The letter must be from your PWS Official and must include an explanation as to why the 

UCMR requirements are applicable to your system along with the appropriate contact information. A 

copy of the letter must also be submitted to the State, as directed by the State. EPA will make an 

applicability determination based on your letter, and in consultation with the State when necessary, and 

will notify you regarding your applicability status and required sampling schedule. However, if your PWS 

meets the applicability criteria specified in §141.40(a)(2)(i), you are subject to the UCMR monitoring and 

reporting requirements, regardless of whether you have been notified by the State or EPA. 

(5) Notifying EPA if your PWS cannot sample according to schedule . 

(i) General rescheduling notification requirements . Large systems may change their Assessment 

Monitoring (List 1) or Screening Survey (List 2) schedule up to August 2, 2007 using EPA's electronic 

data reporting system, as specified in paragraph (b)(1) of this section. After these dates have passed, if 

your PWS cannot sample according to your assigned sampling schedule (e.g., because of budget 

constraints, or if a sampling location will be closed during the scheduled month of monitoring), you must 

fax, mail, or e-mail a letter to EPA, as specified in paragraph (b)(1) of this section, prior to the scheduled 

sampling date. You must include an explanation of why the samples cannot be taken according to the 

assigned schedule and the alternative schedule you are requesting. You are subject to your assigned 

UCMR sampling schedule or the schedule that you revised on or before August 2, 2007, unless and until 

you receive a letter from EPA specifying a new schedule. 

(ii) Exceptions to the rescheduling notification requirements . For ground water sampling, if the second 

round of sampling will be completed five to seven months after the first sampling event, as specified in 

Table 2 of §141.40(a)(4)(i)(B), no notification to EPA is required. If any ground water sampling location 

will be non-operational for more than one month before and one month after the month in which the 

second sampling event is scheduled ( i.e. , it is not possible for you to sample within the five to seven 

month window), you must notify EPA, as specified in paragraph (b)(1) of this section, explaining why the 

schedule cannot be met. You must comply with any modified schedule provided by EPA. 

(6) Reporting monitoring results . For each sample, you must report the information specified in Table 1 

of paragraph (e) of this section, using EPA's electronic data reporting system, as follows. If you are 

conducting Assessment Monitoring, you must include data elements 1 through 5, and 7 through 15 in 

paragraph (e) of this section; and if you are conducting Screening Survey monitoring, you must include 

elements 1 through 15. You also must report any changes made to data elements 1 through 6 to EPA, in 

writing, explaining the nature and purpose of the proposed change, as specified in paragraph (b)(1) of 

this section. 

(i) Electronic reporting system . You are responsible for ensuring that the laboratory conducting the 

analysis of your unregulated contaminant monitoring samples (your laboratory) posts the analytical 

results to EPA's electronic reporting system. You are also responsible for reviewing, approving, and 

submitting those results to EPA. 

(ii) Reporting schedule . You must ensure that your laboratory posts the data to EPA's electronic data 

reporting system within 120 days from the sample collection date (sample collection must occur as 

specified in §141.40(a)(4)). You have 60 days from when the laboratory posts the data in EPA's 

electronic data reporting system to review, approve, and submit the data to the State and EPA, at the 

Web address specified in paragraph (b)(1) of this section. If you do not take action on the data within 60 

days of the laboratory's posting to the electronic reporting system, the data will be considered approved 

by you, and available for EPA and State review. 

(7) Only one set of results accepted . If you report more than one set of valid results for the same 

sampling location and the same sampling event (for example, because you have had more than one 

laboratory analyze replicate samples collected under §141.40(a)(5), or because you have collected 

multiple samples during a single monitoring event at the same sampling location), EPA will use the 

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highest of the reported values as the official result. 

(8) No reporting of previously collected data . You cannot report previously collected data to meet the 

testing and reporting requirements for the contaminants listed in §141.40(a)(3). All analyses must be 

performed by laboratories approved by EPA to perform UCMR analyses using the analytical methods 

specified in Table 1 of §141.40(a)(3) and using samples collected according to §141.40(a)(4). Such 

requirements preclude the possibility of “grandfathering” previously collected data. 

(d) Reporting by small systems. If you serve a population of 10,000 or fewer people, and you are notified 

that you have been selected for UCMR monitoring, your reporting requirements will be specified within 

the materials that EPA sends you, including a request for contact information, and a request for 

information associated with the sampling kit. 

(1) Contact information. EPA will send you a notice requesting contact information for key individuals at 

your system, including name, affiliation, mailing address, phone number, fax number, and e-mail 

address. These individuals include your PWS Technical Contact and your PWS Official. You are 

required to provide this information within 90 days of receiving the notice from EPA as specified in 

paragraph (b)(1) of this section. If this information changes, you also must provide updates within 30 

days of the change, as specified in paragraph (b)(1) of this section. 

(2) Reporting sampling information. You must record data elements listed in Table 1 of paragraph (e) of 

this section on each sample form and sample bottle provided to you by the UCMR Sampling 

Coordinator, as follows: If you are conducting Assessment Monitoring, you must include elements 1 

through 5, and 7; if you are conducting Screening Survey, you must include elements 1 through 7. You 

must send this information as specified in the instructions of your sampling kit, which will include the due 

date and return address. You must report any changes made in data elements 1 through 6 by mailing or 

e-mailing an explanation of the nature and purpose of the proposed change to EPA, as specified in 

paragraph (b)(1) of this section. 

(e) Data elements. Table 1 defines the data elements that must be provided with UCMR sample results. 

Table 1—Unregulated Contaminant Monitoring Reporting Requirements 

Data element Definition

1. Public Water 

System 

Identification 

(PWSID) Code

The code used to identify each PWS. The code begins with 

the standard 2-character postal State abbreviation or 

Region code; the remaining 7 numbers are unique to each 

PWS in the State. The same identification code must be 

used to represent the PWS identification for all current and 

future UCMR monitoring.

2. Public Water 

System Facility 

Identification 

Code

An identification code established by the State or, at the 

State's discretion, by the PWS, following the format of a 5-

digit number unique within each PWS for each applicable 

facility ( i.e. , for each source of water, treatment plant, 

distribution system, or any other facility associated with 

water treatment or delivery). The same identification code 

must be used to represent the facility for all current and 

future UCMR monitoring.

3. Water Source 

Type

The type of source water that supplies a water system 

facility. Systems must report one of the following codes for 

each sampling location:

 SW= surface water (to be reported for water facilities that 

are served all or in part by a surface water source at any 

time during the twelve-month period).

 GW= ground water (to be reported for water facilities that 

are served entirely by a ground water source).

 GU= ground water under the direct influence of surface 

water (to be reported for water facilities that are served all 

or in part by ground water under the direct influence of 

surface water at any time during the twelve-month sampling 

period), and are not served at all by surface water during 

this period.

4. Sampling 

Point 

Identification 

Code

An identification code established by the State, or at the 

State's discretion, by the PWS, that uniquely identifies each 

sampling point. Each sampling code must be unique within 

each applicable facility, for each applicable sampling 

location ( i.e. , entry point to the distribution system or 

distribution system sample at maximum residence time). 

The same identification code must be used to represent the 

sampling location for all current and future UCMR 

monitoring.

5. Sampling 

Point Type Code

A code that identifies the location of the sampling point as 

either:

 EP= entry point to the distribution system.

 MR= distribution system sample at maximum residence 

time.

6. Disinfectant 

Residual Type

The type of disinfectant in use at the time of UCMR 

sampling to maintain a residual in the distribution system for 

each Screening Survey sampling point. To be reported by 

systems required to conduct Screening Survey monitoring. 

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[72 FR 389, Jan. 4, 2007] 

Subpart E—Special Regulations, Including Monitoring Regulations and Prohibition on 

Lead Use 

 top

§ 141.40 Monitoring requirements for unregulated contaminants. 

 top

Systems must report using the following codes for each 

Screening Survey sampling location ( i.e. , EP, MR):

 CL= chlorine

 CA= chloramine

 OT= all other types of disinfectant (e.g., chlorine dioxide)

 ND= no disinfectant used.

7. Sample 

Collection Date

The date the sample is collected, reported as 4-digit year, 

2-digit month, and 2-digit day.

8. Sample 

Identification 

Code

An alphanumeric value up to 30 characters assigned by the 

laboratory to uniquely identify containers, or groups of 

containers, containing water samples collected at the same 

sampling location for the same sampling date.

9. Contaminant The unregulated contaminant for which the sample is being 

analyzed.

10. Analytical 

Method Code

The identification code of the analytical method used.

11. Sample 

Analysis Type

The type of sample collected and/or prepared, as well as 

the fortification level. Permitted values include:

 FS= field sample; sample collected and submitted for 

analysis under this rule.

 LFSM= laboratory fortified sample matrix; a UCMR field 

sample with a known amount of the contaminant of interest 

added.

 LFSMD= laboratory fortified sample matrix duplicate; 

duplicate of the laboratory fortified sample matrix.

 CF= concentration fortified; reported with sample analysis 

types LFSM and LFSMD, the concentration of a known 

contaminant added to a field sample.

12. Analytical 

Results—Sign

A value indicating whether the sample analysis result was:

 (<) “less than” means the contaminant was not detected, or 

was detected at a level below the Minimum Reporting 

Level.

 (=) “equal to” means the contaminant was detected at the 

level reported in “Analytical Result—Value.”

13. Analytical 

Result—Value

The actual numeric value of the analytical results for: field 

samples; laboratory fortified matrix samples; laboratory 

fortified sample matrix duplicates; and concentration 

fortified.

14. Laboratory 

Identification 

Code

The code, assigned by EPA, used to identify each 

laboratory. The code begins with the standard twocharacter State postal abbreviation; the remaining five 

numbers are unique to each laboratory in the State.

15. Sample 

Event Code

A code assigned by the PWS for each sample event. This 

will associate samples with the PWS monitoring plan to 

allow EPA to track compliance and completeness. Systems 

must assign the following codes:

 SE1= represents samples collected to meet the UCMR 

monitoring requirement for the first sampling period (all 

source types).

 SE2= represents samples collected to meet the UCMR 

monitoring requirement for the second sampling period (all 

source types).

 SE3= represents samples collected to meet the UCMR 

monitoring requirement for the third sampling period 

(surface water and ground water under the direct influence 

of surface water (GWUDI) sources only).

 SE4= represents samples collected to meet the UCMR 

monitoring requirement for the fourth sampling period 

(surface water and GWUDI sources only).

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(a) General applicability. This section specifies the monitoring and quality control requirements that must 

be followed if you own or operate a public water system (PWS) that is subject to the Unregulated 

Contaminant Monitoring Regulation (UCMR), as specified in paragraphs (a)(1) and (2) of this section. In 

addition, this section specifies the UCMR requirements for State and Tribal participation. For the 

purposes of this section, PWS “population served,” “State,” “ PWS Official,” “PWS Technical Contact,” 

and “finished water” apply as defined in §141.35(a). The determination of whether a PWS is required to 

monitor under this rule is based on the type of system (e.g., community water system, non-transient noncommunity water system, etc.); whether the system purchases all of its water, as finished water, from 

another system; and its population served as of June 30, 2005. 

(1) Applicability to transient non-community systems. If you own or operate a transient non-community 

water system, you do not have to monitor that system for unregulated contaminants. 

(2) Applicability to community water systems and non-transient non-community water systems. 

(i) Large systems. If you own or operate a wholesale or retail PWS (other than a transient noncommunity system) that serves more than 10,000 people, and do not purchase your entire water supply 

as finished water from another PWS, you must monitor according to the specifications in this paragraph 

(a)(2)(i). If you believe that your applicability status is different than EPA has specified in the notification 

letter that you received, or if you are subject to UCMR requirements and you have not been notified by 

either EPA or your State, you must report to EPA, as specified in §141.35(b)(2) or (c)(4). 

(A) Assessment Monitoring. You must monitor for the unregulated contaminants on List 1 of Table 1, 

UCMR Contaminant List, in paragraph (a)(3) of this section. If you serve a population of more than 

10,000 people, you are required to perform this monitoring regardless of whether you have been notified 

by the State or EPA. 

(B) Screening Survey. You must monitor for the unregulated contaminants on List 2 (Screening Survey) 

of Table 1, as specified in paragraph (a)(3) of this section, if your system serves 10,001 to 100,000 

people and you are notified by EPA or your State that you are part of the State Monitoring Plan for 

Screening Survey testing. If your system serves more than 100,000 people, you are required to conduct 

this Screening Survey testing regardless of whether you have been notified by the State or EPA. 

(C) Pre-Screen Testing. You must monitor for the unregulated contaminants on List 3 of Table 1, in 

paragraph (a)(3) of this section, if notified by your State or EPA that you are part of the Pre-Screen 

Testing. 

(ii) Small systems. Small PWSs, as defined in this paragraph, will not be selected to monitor for any 

more than one of the three monitoring lists provided in Table 1, UCMR Contaminant List, in paragraph 

(a)(3) of this section. EPA will provide sample containers, provide pre-paid air bills for shipping the 

sampling materials, conduct the laboratory analysis, and report and review monitoring results for all 

small systems selected to conduct monitoring under paragraphs (a)(2)(ii)(A) through (C) of this section. 

If you own or operate a PWS (other than a transient system) that serves 10,000 or fewer people and do 

not purchase your entire water supply from another PWS, you must monitor as follows: 

(A) Assessment Monitoring. You must monitor for the unregulated contaminants on List 1 of Table 1, in 

paragraph (a)(3) of this section, if you are notified by your State or EPA that you are part of the State 

Monitoring Plan for Assessment Monitoring. 

(B) Screening Survey. You must monitor for the unregulated contaminants on List 2 of Table 1, in 

paragraph (a)(3) of this section, if notified by your State or EPA that you are part of the State Monitoring 

Plan for the Screening Survey. 

(C) Pre-Screen Testing. You must monitor for the unregulated contaminants on List 3 of Table 1, in 

paragraph (a)(3) of this section, if you are notified by your State or EPA that you are part of the State 

Monitoring plan for Pre-Screen Testing. 

(3) Analytes to be monitored. Lists 1, 2, and 3 of unregulated contaminants are provided in the following 

table: 

Table 1—UCMR Contaminant List 

[List 1: Assessment Monitoring Chemical Contaminants] 

1—Contaminant

2—CAS 

registry 

number

3—

Analytical 

methodsa

4—

Minimum 

reporting 

levelb

5—

Sampling 

locationc

6—Period 

during 

which 

monitoring 

to be 

completed

Dimethoate 60–51–5 EPA 527d 0.7 μg/L EPTDS 1/1/2008–

12/31/2010

Terbufos sulfone 56070–

16–7

EPA 527d 0.4 μg/L EPTDS 1/1/2008–

12/31/2010

2,2',4,4'-

tetrabromodiphenyl 

ether (BDE–47)

5436–

43–1

EPA 527d 0.3 μg/L EPTDS 1/1/2008–

12/31/2010

2,2',4,4',5-

pentabromodiphenyl 

ether (BDE–99)

60348–

60–9

EPA 527d 0.9 μg/L EPTDS 1/1/2008–

12/31/2010

2,2',4,4',5,5'-

hexabromobiphenyl 

(HBB)

59080–

40–9

EPA 527d 0.7 μg/L EPTDS 1/1/2008–

12/31/2010

2,2',4,4',5,5'-

hexabromodiphenyl 

ether (BDE–153)

68631–

49–2

EPA 527d 0.8 μg/L EPTDS 1/1/2008–

12/31/2010

2,2',4,4',6- 189084– 0.5 μg/L EPTDS 1/1/2008–

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Table 1—UCMR Contaminant List 

[List 2: Screening Survey Chemical Contaminants 

Table 1—UCMR Contaminant List 

[List 3: Pre-Screen Testing to be Sampled After Notice of Analytical Methods Availability] 

pentabromodiphenyl 

ether (BDE–100)

64–8 EPA 527d 12/31/2010

1,3-dinitrobenzene 99–65–0 EPA 529e 0.8 μg/L EPTDS 1/1/2008–

12/31/2010

2,4,6-trinitrotoluene 

(TNT)

118–96–

7

EPA 529e 0.8 μg/L EPTDS 1/1/2008–

12/31/2010

Hexahydro-1,3,5-

trinitro-1,3,5-triazine 

(RDX)

121–82–

4

EPA 529e 1 μg/L EPTDS 1/1/2008–

12/31/2010

1—Contaminant

2—CAS 

registry 

number

3—

Analytical 

methodsa

4—

Minimum 

reporting 

levelb

5—

Sampling 

locationc

6—Period 

during 

which 

monitoring 

to be 

completed

Acetanilide Pesticide Degradation Products

Acetochlor ESA 187022–

11–3

EPA 535f 1 μg/L EPTDS 1/1/2008–

12/31/2010

Acetochlor OA 184992–

44–4

EPA 535f 2 μg/L EPTDS 1/1/2008–

12/31/2010

Alachlor ESA 142363–

53–9

EPA 535f 1 μg/L EPTDS 1/1/2008–

12/31/2010

Alachlor OA 171262–

17–2

EPA 535f 2 μg/L EPTDS 1/1/2008–

12/31/2010

Metolachlor ESA 171118–

09–5

EPA 535f 1 μg/L EPTDS 1/1/2008–

12/31/2010

Metolachlor OA 152019–

73–3

EPA 535f 2 μg/L EPTDS 1/1/2008–

12/31/2010

Acetanilide Pesticide Parent Compounds

Acetochlor 34256–

82–1

EPA 

525.2g

2 μg/L EPTDS 1/1/2008–

12/31/2010

Alachlor 15972–

60–8

EPA 

525.2g

2 μg/L EPTDS 1/1/2008–

12/31/2010

Metolachlor 51218–

45–2

EPA 

525.2g

1 μg/L EPTDS 1/1/2008–

12/31/2010

Nitrosamines

Nnitrosodiethylamine 

(NDEA)

55–18–5 EPA 521h 0.005 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

N-nitrosodimethylamine 

(NDMA)

62–75–9 EPA 521h 0.002 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

N-nitroso-di-nbutylamine (NDBA)924–16–

3

EPA 521h 0.004 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

N-nitroso-di-npropylamine 

(NDPA)

621–64–

7

EPA 521h 0.007 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

N-nitrosomethylethylamine 

(NMEA)

10595–

95–6

EPA 521h 0.003 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

N-nitrosopyrrolidine 

(NPYR)

930–55–

2

EPA 521h 0.002 

μg/L

DSMRT 

and 

EPTDS

1/1/2008–

12/31/2010

1—

Contaminant

2—CAS 

registry 

number

3—

Analytical 

methodsa

4—

Minimum 

reporting 

levelb

5—

Sampling 

locationc

6—Period 

during which 

monitoring to 

be completed

Reservedi Reservedi Reservedi Reservedi Reservedi Reservedi

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Column headings are: 

1—Contaminant: The name of the contaminant to be analyzed. 

2—CAS (Chemical Abstract Service) Registry Number or Identification Number: A unique number 

identifying the chemical contaminants. 

3—Analytical Methods: method numbers identifying the methods that must be used to test the 

contaminants. 

4—Minimum Reporting Level: The value and unit of measure at or above which the concentration of the 

contaminant must be measured using the approved analytical methods. 

5—Sampling Location: The locations within a PWS at which samples must be collected. 

6—Period During Which Monitoring To Be Completed: The dates during which the sampling and testing 

are to occur for the indicated contaminant. 

The analytical procedures shall be performed in accordance with the documents associated with each 

method (per the following footnotes). The incorporation by reference of the following documents listed in 

footnotes d—h was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) 

and 1 CFR part 51. Information on how to obtain these documents can be provided by the Safe Drinking 

Water Hotline at (800) 426–4791. Documents may be inspected at EPA's Drinking Water Docket, 1301 

Constitution Avenue, NW., EPA West, Room B102, Washington, DC 20460, Telephone: (202) 566–

2426; or at the National Archives and Records Administration (NARA). For information on availability of 

this material at NARA, call 202–741–6030, or go to: http://www.archives.gov/federal-register/index.html. 

aThe version of the EPA methods which you must follow for this Regulation are listed in d—h as follows.

bThe Minimum Reporting Level (MRL) was established by EPA by adding the mean of the Lowest 

Concentration Minimum Reporting Levels (LCMRL) determined according to the procedure detailed in 

“Statistical Protocol for the Determination of The Single-Laboratory Lowest Concentration Minimum 

Reporting Level (LCMRL) and Validation of the Minimum Reporting Level (MRL)” by the primary and 

secondary laboratories conducting the development and validation of the analytical method to three 

times the difference of the LCMRLs. If LCMRL data from three or more laboratories were available, the 

MRL was established by EPA by adding three times the standard deviation of the LCMRLs to the mean 

of the LCMRLs. Note that EPA Method 525.2 was developed prior to UCMR 2, hence the LCMRLs were 

not determined for analytes determined by this method. 

cSampling must occur at entry points to the distribution system (EPTDSs) after treatment is applied that 

represent each non-emergency water source in routine use over the 12-month period of monitoring. See 

40 CFR 141.35(c)(3) for an explanation of the requirements related to use of representative EPTDSs. 

Sampling for nitrosamines on List 2 must also occur at the disinfection byproduct distribution system 

maximum residence time (DSMRT) sampling locations as defined in 40 CFR 141.132(b)(1)(i) and at 

EPTDS sampling locations. If a treatment plant/water source is not subject to the sampling required in 

40 CFR 141.132(b)(1), then the samples for nitrosamines must be collected only at the EPTDS location

(s). 

dEPA Method 527 “Determination of Selected Pesticides and Flame Retardants in Drinking Water by 

Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS),” 

Revision 1.0, April 2005 is available at http://www.epa.gov/safewater/methods/sourcalt.html. 

eEPA Method 529 “Determination of Explosives and Related Compounds in Drinking Water by Solid 

Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS),” Revision 

1.0, September 2002 is available at http://www.epa.gov/nerlcwww/ordmeth.htm. 

f

EPA Method 535 “ Measurement of Chloroacetanilide and Other Acetamide Herbicide Degradates in 

Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry 

(LC/MS/MS),” Version 1.1, April 2005 is available at http://www.epa.gov/nerlcwww/ordmeth.htm. 

gEPA Method 525.2 “Determination of Organic Compounds in Drinking Water by Liquid-Solid Extraction 

and Capillary Column Gas Chromatography/Mass Spectrometry,” Revision 2.0, 1995 is available at 

http://www.NEMI.gov. 

hEPA Method 521 “Determination of Nitrosamines in Drinking Water by Solid Phase Extraction and 

Capillary Column Gas Chromatography with Large Volume Injection and Chemical Ionization Tandem 

Mass Spectrometry (MS/MS),” Version 1.0, September 2004 is available at 

http://www.epa.gov/nerlcwww/ordmeth.htm. 

i

To be determined at a later time.

(4) Sampling requirements —(i) Large systems. If you serve more than 10,000 people and meet the 

UCMR applicability criteria specified in paragraph (a)(2)(i) of this section, you must comply with the 

requirements specified in paragraphs (a)(4)(i)(A) through (I) of this section. Your samples must be 

collected according to the schedule that you are assigned by EPA or your State, or the schedule that 

you revised using EPA's electronic data reporting system on or before August 2, 2007. Your schedule 

must follow both the timing and frequency of monitoring specified in Tables 1 and 2 of this section. 

(A) Monitoring period. You must collect the samples in one continuous 12-month period for List 1 

Assessment Monitoring, and, if applicable, for List 2 Screening Survey, or List 3 Pre-Screen Testing, 

during the time frame indicated in column 6 of Table 1, in paragraph (a)(3) of this section. EPA or your 

State will specify the month(s) and year(s) in which your monitoring must occur. As specified in §141.35

(c)(5), you must contact EPA if you believe you cannot conduct monitoring according to your schedule. 

(B) Frequency. You must collect the samples within the time frame and according to the frequency 

specified by contaminant type and water source type for each sampling location, as specified in Table 2, 

in this paragraph, with the following exception. For the second round of ground water sampling, if a 

sample location is non-operational for more than one month before and one month after the scheduled 

sampling month ( i.e. , it is not possible for you to sample within the five to seven month window 

specified the Table 2, in this paragraph), you must notify EPA as specified in §141.35(c)(5). 

Table 2—Monitoring Frequency by Contaminant and Water Source Types 

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(C) Location. You must collect samples for each List 1 Assessment Monitoring contaminant, and, if 

applicable, for each List 2 Screening Survey, or List 3 Pre-Screen Testing contaminant, as specified in 

Table 1, in paragraph (a)(3) of this section. Samples must be collected at each sample point that is 

specified in column 5 of Table 1, in paragraph (a)(3) of this section. If you are a ground water system 

with multiple EPTDSs, and you request and receive approval from EPA or the State for sampling at 

representative EPTDS(s), as specified in §141.35(c)(3), you must collect your samples from the 

approved representative sampling location(s). Systems conducting Screening Survey monitoring must 

also sample for nitrosamines at the disinfection byproduct distribution system maximum residence time 

(DSMRT) sampling location(s) if they are subject to sampling requirements in §141.132(b)(1). 

(D) Sampling instructions. For each List 1 Assessment Monitoring contaminant, and, if applicable, for 

each List 2 Screening Survey, or List 3 Pre-Screen Testing contaminant, you must follow the sampling 

procedure for the method specified in column 3 of Table 1, in paragraph (a)(3) of this section. In 

addition, you must not composite (that is, combine, mix, or blend) the samples; you must collect and 

preserve each sample separately. Samples collected for the analysis of Acetanilide “parent” pesticides 

and their degradation products (Methods 525.2 and 535) must be collected at the same sampling point, 

at the same time. 

(E) Sample collection and shipping time. If you must ship the samples for analysis, you must collect the 

samples early enough in the day to allow adequate time to send the samples for overnight delivery to the 

laboratory. You should not collect samples on Friday, Saturday, or Sunday because sampling on these 

days may not allow samples to be shipped and received at the laboratory at the required temperature, 

unless you have made special arrangements with your laboratory to receive the samples. 

(F) Analytical methods. For each contaminant, you must use the respective analytical methods for List 1, 

and, if applicable, for List 2, or List 3 that are specified in column 3 of Table 1, in paragraph (a)(3) of this 

section; report values at or above the minimum reporting levels for List 1, and, if applicable, for List 2 

Screening Survey, or List 3 Pre-Screen Testing, that are specified in column 4 of Table 1, in paragraph 

(a)(3) of this section; and conduct the quality control procedures specified in paragraph (a)(5) of this 

section. 

(G) Laboratory errors or sampling deviations. If the laboratory data do not meet the required QC criteria, 

as specified in paragraph (a)(5) of this section, or you do not follow the required sampling procedures, 

as specified in paragraphs (a)(4) of this section, you must resample within 30 days of being informed or 

becoming aware of these facts. This resampling is not for the purpose of confirming previous results, but 

to correct the sampling or laboratory error. All systems must report the results obtained from the first 

sampling for each sampling period, except for cases of sampling or laboratory errors. For the purposes 

of this rule, no samples are to be recollected for the purposes of confirming the results observed in a 

previous sampling. 

(H) Analysis. For the List 1 contaminants, and, if applicable, List 2 Screening Survey, or List 3 PreScreen Testing contaminants, identified in Table 1, paragraph (a)(3) of this section, you must arrange for 

testing by a laboratory that has been approved by EPA according to requirements in paragraph (a)(5)(ii) 

of this section. 

(I) Review and reporting of results. After you have received the laboratory results, you must review, 

approve, and submit the system information, and sample collection data and test results. You must 

report the results as provided in §141.35(c)(6). 

(ii) Small systems. If you serve 10,000 or fewer people and are notified that you are part of the State 

Monitoring Plan for Assessment Monitoring, Screening Survey or Pre-Screen monitoring, you must 

comply with the requirements specified in paragraphs (a)(4)(i)(A) through (H) of this section. If EPA or 

the State informs you that they will be collecting your UCMR samples, you must assist them in 

identifying the appropriate sampling locations and in collecting the samples. 

(A) Monitoring period and frequency. You must collect samples at the times specified for you by the 

State or EPA. Your schedule must follow both the timing of monitoring specified in Table 1, List 1, and, if 

applicable, List 2, or List 3, and the frequency of monitoring in Table 2 of this section. 

(B) Location. You must collect samples at the locations specified for you by the State or EPA. 

(C) Sample kits. You must store and maintain the sample collection kits sent to you by the UCMR 

Sampling Coordinator in accordance with the kit's instructions. The sample kit will include all necessary 

containers, packing materials and cold packs, instructions for collecting the sample and sample 

treatment (such as dechlorination or preservation), report forms for each sample, contact name and 

telephone number for the laboratory, and a prepaid return shipping docket and return address label. If 

any of the materials listed in the kit's instructions are not included in the kit or arrive damaged, you must 

notify the UCMR Sampling Coordinator who sent you the sample collection kits. 

(D) Sampling instructions. You must comply with the instructions sent to you by the State or EPA 

concerning the use of containers, collection (how to fill the sample bottle), dechlorination and/or 

preservation, and sealing and preparation of sample and shipping containers for shipment. You must not 

Contaminant 

type Water source type

Time 

frame Frequency

Chemical Surface water or ground water 

under the direct influence of 

surface water (GWUDI) 

(includes all sampling locations 

for which some or all of the 

water comes from a surface 

water or GWUDI source at any 

time during the 12 month 

monitoring period)

12 

months

You must monitor 

for 4 consecutive 

quarters. Sample 

events must occur 3 

months apart.

 Ground water 12 

months

You must monitor 

twice in a 

consecutive 12-

month period. 

Sample events must 

occur 5–7 months 

apart.

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composite (that is, combine, mix, or blend) the samples. You also must collect, preserve, and test each 

sample separately. You must also comply with the instructions sent to you by the UCMR Sampling 

Coordinator concerning the handling of sample containers for specific contaminants. 

(E) Sampling deviations. If you do not collect a sample according to the instructions provided to you for a 

listed contaminant, you must report the deviation within 7 days of the scheduled monitoring on the 

sample reporting form, as specified in §141.35(d)(2). You must resample following instructions that you 

will be sent from the UCMR Sampling Coordinator or State. A copy of the form must be sent to the 

laboratory with the recollected samples, and to the UCMR Sampling Coordinator. 

(F) Duplicate samples. EPA will select a subset of systems in the State Monitoring Plan that must collect 

duplicate samples for quality control. If your system is selected, you will receive two sample kits for an 

individual sampling location that you must use. You must use the same sampling protocols for both sets 

of samples, following the instructions in the duplicate sample kit. 

(G) Sampling forms. You must completely fill out each of the sampling forms and bottles sent to you by 

the UCMR Sampling Coordinator, including data elements listed in §141.35(e) for each sample. If you 

are conducting Assessment Monitoring, you must include elements 1 through 5, and 7; and if you are 

conducting Screening Survey, you must include elements 1 through 7. You must sign and date the 

sampling forms. 

(H) Sample collection and shipping. You must collect the samples early enough in the day to allow 

adequate time to send the samples for overnight delivery to the laboratory. You should not collect 

samples on Friday, Saturday, or Sunday because sampling on these days may not allow samples to be 

shipped and received at the laboratory at the required temperature unless you have made special 

arrangements with EPA for the laboratory to receive the samples. Once you have collected the samples 

and completely filled in the sampling forms, you must send the samples and the sampling forms to the 

laboratory designated on the air bill. 

(5) Quality control requirements. If your system serves more than 10,000 people, you must ensure that 

the quality control requirements listed below are met during your sampling procedures and by the 

laboratory conducting your analyses. You must also ensure that all method quality control procedures 

and all UCMR quality control procedures are followed. 

(i) Sample collection/preservation . You must follow the sample collection and preservation requirements 

for the specified method for each of the contaminants in Table 1, in paragraph (a)(3) of this section. 

These requirements specify sample containers, collection, dechlorination, preservation, storage, sample 

holding time, and extract storage and/or holding time that you must assure that the laboratory follow. 

(ii) Laboratory approval for Lists 1, List 2 and List 3. To be approved to conduct UCMR testing, the 

laboratory must be certified under §141.28 for one or more compliance analyses; demonstrate for each 

analytical method it plans to use for UCMR testing that it can meet the Initial Demonstration of Capability 

(IDC) requirements detailed in the analytical methods specified in column 3 of Table 1, in paragraph (a)

(3) of this section; and successfully participate in the UCMR Proficiency Testing (PT) Program 

administered by EPA for each analytical method it plans to use for UCMR testing. UCMR laboratory 

approval decisions will be granted on an individual method basis for the methods listed in column 3 of 

Table 1 in paragraph (a)(3) of this section for List 1, List 2, and List 3 contaminants. Laboratory approval 

is contingent upon the capability of the laboratory to post monitoring data to the EPA electronic data 

reporting system. To participate in the UCMR Laboratory Approval Program, the laboratory must 

complete and submit the necessary registration forms by April 4, 2007. Correspondence must be 

addressed to: UCMR 2 Laboratory Approval Coordinator, USEPA, Technical Support Center, 26 West 

Martin Luther King Drive (MS 140), Cincinnati, OH 45268; or e-mailed to EPA at 

UCMR_Sampling_Coordinator@epa.gov . 

(iii) Minimum Reporting Level. The MRL is the lowest analyte concentration for which future recovery is 

predicted to fall, with high confidence (at least 99%), between 50% and 150% recovery. 

(A) Validation of laboratory performance. Your laboratory must be capable of quantifying each 

contaminant listed in Table 1, at or below the MRL specified in column 4 of Table 1, in paragraph (a)(3) 

of this section. You must ensure that the laboratory completes and has on file and available for your 

inspection, records of two distinct procedures. First, your laboratory must have conducted an IDC 

involving replicate analyses at or below the MRL as described in this paragraph. Second, for each day 

that UCMR analyses are conducted by your laboratory, a validation of its ability to quantify each 

contaminant, at or below the MRL specified in column 4 of Table 1, in paragraph (a)(3) of this section, 

following the procedure listed in paragraph (a)(5)(iii)(B) of this section, must be performed. The 

procedure for initial validation of laboratory performance at or below the MRL is as follows: 

( 1 ) All laboratories using EPA drinking water methods under UCMR must demonstrate that they are 

capable of meeting data quality objectives (DQOs) at or below the MRL listed in Table 1, column 4, in 

paragraph (a)(3) of this section. 

( 2 ) The MRL, or any concentration below the MRL, at which performance is being evaluated, must be 

contained within the range of calibration. The calibration curve regression model and the range of 

calibration levels that are used in these performance validation steps must be used in all routine sample 

analyses used to comply with this regulation. Only straight line or quadratic regression models are 

allowed. The use of either weighted or unweighted models is permitted. The use of cubic regression 

models is not permitted. 

( 3 ) Replicate analyses of at least seven (7) fortified samples in reagent water must be performed at or 

below the MRL for each analyte, and must be processed through the entire method procedure ( i.e. , 

including extraction, where applicable, and with all preservatives). 

( 4 ) A prediction interval of results (PIR), which is based on the estimated arithmetic mean of analytical 

results and the estimated sample standard deviation of measurement results, must be determined by 

Equation 1: 

Where: 

t is the Student's t value with df degrees of freedom and confidence level (1–α), 

s is the sample standard deviation of n replicate samples fortified at the MRL, 

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n is the number of replicates. 

( 5 ) The values needed to calculate the PIR using Equation 1 are: Number of replicates ( n ); Student's t 

value with a two-sided 99% confidence level for n number of replicates; the average (mean) of at least 

seven replicates; and the sample standard deviation. Factor 1 is referred to as the Half Range PIR 

(HRPIR). 

For a certain number of replicates and for a certain confidence level in Student's t , this factor 

is constant, and can be tabulated according to replicate number and confidence level for the Student's t . 

Table 3 in this paragraph lists the constant factor ( C ) for replicate sample numbers 7 through 10 with a 

confidence level of 99% for Student's t . 

( 6 ) The HRPIR is calculated by Equation 2: 

( 7 ) The PIR is calculated by Equation 3: 

Table 3—The Constant Factor (C) to be Multiplied by the Standard Deviation to Determine the 

Half Range Interval of the PIR (Student's t 99% Confidence Level)a

aThe critical t -value for a two-sided 99% confidence interval is equivalent to the critical t -value for a 

one-sided 99.5% confidence interval, due to the symmetry of the t -distribution. PIR = Prediction Interval 

of Results. 

( 8 ) The lower and upper result limits of the PIR must be converted to percent recovery of the 

concentration being tested. To pass criteria at a certain level, the PIR lower recovery limits cannot be 

lower than the lower recovery limits of the QC interval (50%), and the PIR upper recovery limits cannot 

be greater than the upper recovery limits of the QC interval (150%). When either of the PIR recovery 

limits falls outside of either bound of the QC interval of recovery (higher than 150% or less than 50%), 

laboratory performance is not validated at the concentration evaluated. If the PIR limits are contained 

within both bounds of the QC interval, laboratory performance is validated for that analyte. 

(B) Quality control requirements for validation of laboratory performance at or below the MRL. 

( 1 ) You must ensure that the calibration curve regression model and that the range of calibration levels 

that are used in these performance validation steps are used in future routine sample analysis. Only 

straight line or quadratic regression models are allowed. The use of either weighted or unweighted 

models is permitted. The use of cubic regression models is not permitted. 

( 2 ) You must ensure, once your laboratory has performed an IDC as specified in each analytical 

method (demonstrating that DQOs are met at or below an MRL), that a daily performance check is 

performed for each analyte and method. A single laboratory blank, fortified at or below the MRL for each 

analyte, must be processed through the entire method procedure. The measured concentration for each 

analyte must be converted to a percent recovery, and if the recovery is within 50%–150% (inclusive), the 

daily performance of the laboratory has been validated. The results for any analyte for which 50%–150% 

recovery cannot be demonstrated during the daily check are not valid. Laboratories may elect to re-run 

the daily performance check sample if the performance for any analyte or analytes cannot be validated. 

If performance is validated for these analytes, the laboratory performance is considered validated. 

Alternatively, the laboratory may re-calibrate and repeat the performance validation process for all 

analytes. 

(iv) Laboratory fortified sample matrix and laboratory fortified sample matrix duplicate. You must ensure 

that your laboratory prepares and analyzes the Laboratory Fortified Sample Matrix (LFSM) sample for 

accuracy and Laboratory Fortified Sample Matrix Duplicate (LFSMD) samples for precision to determine 

method accuracy and precision for all contaminants in Table 1, in paragraph (a)(3) of this section. 

LFSM/LFSMD samples must be prepared using a sample collected and analyzed in accordance with 

UCMR 2 requirements and analyzed at a frequency of 5% (or 1 LFSM/LFSMD set per every 20 

samples) or with each sample batch, whichever is more frequent. In addition, the LFSM/LFSMD 

fortification concentrations must be alternated between a low-level fortification and mid-level fortification 

approximately 50% of the time. (For example: A set of 40 samples will require preparation and analysis 

of 2 LFSM/LFSMD sets. The first set must be fortified at either the low-level or mid-level, and the second 

set must be fortified with the other standard, either the low-level or mid-level, whichever was not used for 

the initial LFSM/LFSMD set.) The low-level LFSM/LFSMD fortification concentration must be within 

±50% of the MRL for each contaminant (e.g., for an MRL of 1 μg/L the acceptable fortification levels 

must be between 0.5 μg/L and 1.5 μg/L). The mid-level LFSM/LFSMD fortification concentration must be 

within ±20% of the mid-level calibration standard for each contaminant, and should represent, where 

possible and where the laboratory has data from previously analyzed samples, an approximate average 

concentration observed in previous analyses of that analyte. There are no acceptance criteria specified 

for LFSM/LFSMD analyses. All LFSM/LFSMD data are to be reported. 

Replicates

Degrees of 

freedom

Constant factor (C) to be multiplied by the 

standard 

deviation

7 6 3.963

8 7 3.711

9 8 3.536

10 9 3.409

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(v) Method defined quality control. You must ensure that your laboratory performs Laboratory Fortified 

Blanks and Laboratory Performance Checks, as appropriate to the method's requirements, for those 

methods listed in Table 1, column 3, in paragraph (a)(3) of this section. Each method specifies 

acceptance criteria for these QC checks. 

(vi) Reporting. You must ensure that your laboratory reports the analytical results and other data, with 

the required data listed in Table 1, in §141.35(e). You must require your laboratory to submit these data 

electronically to the State and EPA using EPA's electronic data reporting system, accessible at 

( http://www.epa.gov/safewater/ucmr/ucmr2/reporting.html ), within 120 days from the sample collection 

date. You then have 60 days from when the laboratory posts the data to review, approve, and submit the 

data to the State and EPA, via EPA's electronic data reporting system. If you do not electronically 

approve and submit the laboratory data to EPA within 60 days of the laboratory's posting to EPA's 

electronic reporting system, the data will be considered approved and final for State and EPA review. 

(6) Violation of this rule —(i) Monitoring violations. Any failure to monitor in accordance with §141.40(a)

(3)–(5) is a monitoring violation. 

(ii) Reporting violations. Any failure to report in accordance with §141.35 is a reporting violation. 

(b) Petitions and waivers by States —(1) Governors' petition for additional contaminants. The Safe 

Drinking Water Act allows Governors of seven (7) or more States to petition the EPA Administrator to 

add one or more contaminants to the UCMR Contaminant List in paragraph (a)(3) of this section. The 

petition must clearly identify the reason(s) for adding the contaminant(s) to the monitoring list, including 

the potential risk to public health, particularly any information that might be available regarding 

disproportional risks to the health and safety of children, the expected occurrence documented by any 

available data, any analytical methods known or proposed to be used to test for the contaminant(s), and 

any other information that could assist the Administrator in determining which contaminants present the 

greatest public health concern and should, therefore, be included on the UCMR Contaminant List in 

paragraph (a)(3) of this section. 

(2) State-wide waivers. A State can waive monitoring requirements only with EPA approval and under 

very limited conditions. Conditions and procedures for obtaining a waiver are as follows: 

(i) Application. A State may apply to EPA for a State-wide waiver from the unregulated contaminant 

monitoring requirements for PWSs serving more than 10,000 people. To apply for such a waiver, the 

State must submit an application to EPA that includes the following information: The list of contaminants 

on the UCMR Contaminant List for which a waiver is requested, along with documentation for each 

contaminant in the request demonstrating that the contaminants or their parent compounds do not occur 

naturally in the State, and certifying that during the past 15 years they have not been used, applied, 

stored, disposed of, released, or detected in the source waters or distribution systems in the State. 

(ii) Approval. EPA will review State applications and notify the State whether it accepts or rejects the 

request. The State must receive written approval from EPA before issuing a State-wide waiver. 

[72 FR 393, Jan. 4, 2007; 72 FR 3916, Jan. 26, 2007] 

§ 141.41 Special monitoring for sodium. 

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(a) Suppliers of water for community public water systems shall collect and analyze one sample per 

plant at the entry point of the distribution system for the determination of sodium concentration levels; 

samples must be collected and analyzed annually for systems utilizing surface water sources in whole or 

in part, and at least every three years for systems utilizing solely ground water sources. The minimum 

number of samples required to be taken by the system shall be based on the number of treatment plants 

used by the system, except that multiple wells drawing raw water from a single aquifer may, with the 

State approval, be considered one treatment plant for determining the minimum number of samples. The 

supplier of water may be required by the State to collect and analyze water samples for sodium more 

frequently in locations where the sodium content is variable. 

(b) The supplier of water shall report to EPA and/or the State the results of the analyses for sodium 

within the first 10 days of the month following the month in which the sample results were received or 

within the first 10 days following the end of the required monitoring period as stipulated by the State, 

whichever of these is first. If more than annual sampling is required the supplier shall report the average 

sodium concentration within 10 days of the month following the month in which the analytical results of 

the last sample used for the annual average was received. The supplier of water shall not be required to 

report the results to EPA where the State has adopted this regulation and results are reported to the 

State. The supplier shall report the results to EPA where the State has not adopted this regulation. 

(c) The supplier of water shall notify appropriate local and State public health officials of the sodium 

levels by written notice by direct mail within three months. A copy of each notice required to be provided 

by this paragraph shall be sent to EPA and/or the State within 10 days of its issuance. The supplier of 

water is not required to notify appropriate local and State public health officials of the sodium levels 

where the State provides such notices in lieu of the supplier. 

(d) Analyses for sodium shall be conducted as directed in §141.23(k)(1). 

[45 FR 57345, Aug. 27, 1980, as amended at 59 FR 62470, Dec. 5, 1994] 

§ 141.42 Special monitoring for corrosivity characteristics. 

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(a)–(c) [Reserved] 

(d) Community water supply systems shall identify whether the following construction materials are 

present in their distribution system and report to the State: 

Lead from piping, solder, caulking, interior lining of distribution mains, alloys and home 

plumbing. 

Copper from piping and alloys, service lines, and home plumbing. 

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Galvanized piping, service lines, and home plumbing. 

Ferrous piping materials such as cast iron and steel. 

Asbestos cement pipe. 

In addition, States may require identification and reporting of other materials of construction present in 

distribution systems that may contribute contaminants to the drinking water, such as: 

Vinyl lined asbestos cement pipe. 

Coal tar lined pipes and tanks. 

[45 FR 57346, Aug. 27, 1980; 47 FR 10999, Mar. 12, 1982, as amended at 59 FR 62470, Dec. 5, 1994] 

§ 141.43 Prohibition on use of lead pipes, solder, and flux. 

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(a) In general —(1) Prohibition. Any pipe, solder, or flux, which is used after June 19, 1986, in the 

installation or repair of— 

(i) Any public water system, or 

(ii) Any plumbing in a residential or nonresidential facility providing water for human consumption which 

is connected to a public water system shall be lead free as defined by paragraph (d) of this section. This 

paragraph (a)(1) shall not apply to leaded joints necessary for the repair of cast iron pipes. 

(2) [Reserved] 

(b) State enforcement— (1) Enforcement of prohibition. The requirements of paragraph (a)(1) of this 

section shall be enforced in all States effective June 19, 1988. States shall enforce such requirements 

through State or local plumbing codes, or such other means of enforcement as the State may determine 

to be appropriate. 

(2) [Reserved] 

(c) Penalties. If the Administrator determines that a State is not enforcing the requirements of paragraph 

(a) of this section, as required pursuant to paragraph (b) of this section, the Administrator may withhold 

up to 5 percent of Federal funds available to that State for State program grants under section 1443(a) 

of the Act. 

(d) Definition of lead free. For purposes of this section, the term lead free: 

(1) When used with respect to solders and flux refers to solders and flux containing not more than 0.2 

percent lead; 

(2) When used with respect to pipes and pipe fittings refers to pipes and pipe fittings containing not more 

than 8.0 percent lead; and 

(3) When used with respect to plumbing fittings and fixtures intended by the manufacturer to dispense 

water for human ingestion refers to fittings and fixtures that are in compliance with standards established 

in accordance with 42 U.S.C. 300g–6(e). 

[52 FR 20674, June 2, 1987, as amended at 65 FR 2003, Jan. 12, 2000] 

Subpart F—Maximum Contaminant Level Goals and Maximum Residual Disinfectant 

Level Goals 

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§ 141.50 Maximum contaminant level goals for organic contaminants. 

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(a) MCLGs are zero for the following contaminants: 

(1) Benzene 

(2) Vinyl chloride 

(3) Carbon tetrachloride 

(4) 1,2-dichloroethane 

(5) Trichloroethylene 

(6) Acrylamide 

(7) Alachlor 

(8) Chlordane 

(9) Dibromochloropropane 

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(10) 1,2-Dichloropropane 

(11) Epichlorohydrin 

(12) Ethylene dibromide 

(13) Heptachlor 

(14) Heptachlor epoxide 

(15) Pentachlorophenol 

(16) Polychlorinated biphenyls (PCBs) 

(17) Tetrachloroethylene 

(18) Toxaphene 

(19) Benzo[a]pyrene 

(20) Dichloromethane (methylene chloride) 

(21) Di(2-ethylhexyl)phthalate 

(22) Hexachlorobenzene 

(23) 2,3,7,8-TCDD (Dioxin) 

(b) MCLGs for the following contaminants are as indicated: 

[50 FR 46901, Nov. 13, 1985, as amended at 52 FR 20674, June 2, 1987; 52 FR 25716, July 8, 1987; 

56 FR 3592, Jan. 30, 1991; 56 FR 30280, July 1, 1991; 57 FR 31846, July 17, 1992] 

§ 141.51 Maximum contaminant level goals for inorganic contaminants. 

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Contaminant MCLG in mg/l

(1) 1,1-Dichloroethylene 0.007

(2) 1,1,1-Trichloroethane 0.20

(3) para-Dichlorobenzene 0.075

(4) Aldicarb 0.001

(5) Aldicarb sulfoxide 0.001

(6) Aldicarb sulfone 0.001

(7) Atrazine 0.003

(8) Carbofuran 0.04

(9) o-Dichlorobenzene 0.6

(10) cis-1,2-Dichloroethylene 0.07

(11) trans-1,2-Dichloroethylene 0.1

(12) 2,4-D 0.07

(13) Ethylbenzene 0.7

(14) Lindane 0.0002

(15) Methoxychlor 0.04

(16) Monochlorobenzene 0.1

(17) Styrene 0.1

(18) Toluene 1

(19) 2,4,5-TP 0.05

(20) Xylenes (total) 10

(21) Dalapon 0.2

(22) Di(2-ethylhexyl)adipate .4

(23) Dinoseb .007

(24) Diquat .02

(25) Endothall .1

(26) Endrin .002

(27) Glyphosate .7

(28) Hexachlorocyclopentadiene .05

(29) Oxamyl (Vydate) .2

(30) Picloram .5

(31) Simazine .004

(32) 1,2,4-Trichlorobenzene .07

(33) 1,1,2-Trichloroethane .003

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(a) [Reserved] 

(b) MCLGs for the following contaminants are as indicated: 

1This value for arsenic is effective January 23, 2006. Until then, there is no MCLG.

[50 FR 47155, Nov. 14, 1985, as amended at 52 FR 20674, June 2, 1987; 56 FR 3593, Jan. 30, 1991; 

56 FR 26548, June 7, 1991; 56 FR 30280, July 1, 1991; 57 FR 31846, July 17, 1992; 60 FR 33932, 

June 29, 1995; 66 FR 7063, Jan. 22, 2001] 

§ 141.52 Maximum contaminant level goals for microbiological contaminants. 

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MCLGs for the following contaminants are as indicated: 

[54 FR 27527, 27566, June 29, 1989; 55 FR 25064, June 19, 1990; 63 FR 69515, Dec. 16, 1998] 

§ 141.53 Maximum contaminant level goals for disinfection byproducts. 

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MCLGs for the following disinfection byproducts are as indicated: 

[63 FR 69465, Dec. 16, 1998, as amended at 65 FR 34405, May 30, 2000; 71 FR 478, Jan. 4, 2006] 

§ 141.54 Maximum residual disinfectant level goals for disinfectants. 

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MRDLGs for disinfectants are as follows: 

Contaminant MCLG (mg/l)

Antimony 0.006

Arsenic zero1

Asbestos 7 Million fibers/liter (longer than 10 μm).

Barium 2

Beryllium .004

Cadmium 0.005

Chromium 0.1

Copper 1.3

Cyanide (as free Cyanide) .2

Fluoride 4.0

Lead zero

Mercury 0.002

Nitrate 10 (as Nitrogen).

Nitrite 1 (as Nitrogen).

Total Nitrate+Nitrite 10 (as Nitrogen).

Selenium 0.05

Thallium .0005

Contaminant MCLG

(1) Giardia lamblia zero

(2) Viruses zero

(3) Legionella zero

(4) Total coliforms (including fecal coliforms and Escherichia coli ) zero.

(5) Cryptosporidium zero.

Disinfection byproduct

MCLG 

(mg/L)

Bromodichloromethane zero

Bromoform zero

Bromate zero

Chlorite 0.8

Chloroform 0.07

Dibromochloromethane 0.06

Dichloroacetic acid zero

Monochloroacetic acid 0.07

Trichloroacetic acid 0.02

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[63 FR 69465, Dec. 16, 1998] 

§ 141.55 Maximum contaminant level goals for radionuclides. 

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MCLGs for radionuclides are as indicated in the following table: 

[65 FR 76748, Dec. 7, 2000] 

Subpart G—National Primary Drinking Water Regulations: Maximum Contaminant 

Levels and Maximum Residual Disinfectant Levels 

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§ 141.60 Effective dates. 

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(a) The effective dates for §141.61 are as follows: 

(1) The effective date for paragraphs (a)(1) through (a)(8) of §141.61 is January 9, 1989. 

(2) The effective date for paragraphs (a)(9) through (a)(18) and (c)(1) through (c)(18) of §141.61 is July 

30, 1992. 

(3) The effective date for paragraphs (a)(19) through (a)(21), (c)(19) through (c)(25), and (c)(27) through 

(c)(33) of §141.61 is January 17, 1994. The effective date of §141.61(c)(26) is August 17, 1992. 

(b) The effective dates for §141.62 are as follows: 

(1) The effective date of paragraph (b)(1) of §141.62 is October 2, 1987. 

(2) The effective date for paragraphs (b)(2) and (b)(4) through (b)(10) of §141.62 is July 30, 1992. 

(3) The effective date for paragraphs (b)(11) through (b)(15) of §141.62 is January 17, 1994. 

(4) The effective date for §141.62(b)(16) is January 23, 2006. 

[56 FR 3593, Jan. 30, 1991, as amended at 57 FR 31846, July 17, 1992; 59 FR 34324, July 1, 1994; 

66FR 7063, Jan. 22, 2001] 

§ 141.61 Maximum contaminant levels for organic contaminants. 

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(a) The following maximum contaminant levels for organic contaminants apply to community and nontransient, non-community water systems. 

Disinfectant residual MRDLG(mg/L)

Chlorine 4 (as Cl2).

Chloramines 4 (as Cl2).

Chlorine dioxide 0.8 (as ClO2)

Contaminant MCLG

1. Combined radium-226 and radium-228 Zero.

2. Gross alpha particle activity (excluding radon and uranium) Zero.

3. Beta particle and photon radioactivity Zero.

4. Uranium Zero.

CAS No. Contaminant MCL (mg/l)

(1) 75–01–4 Vinyl chloride 0.002

(2) 71–43–2 Benzene 0.005

(3) 56–23–5 Carbon tetrachloride 0.005

(4) 107–06–2 1,2-Dichloroethane 0.005

(5) 79–01–6 Trichloroethylene 0.005

(6) 106–46–7 para-Dichlorobenzene 0.075

(7) 75–35–4 1,1-Dichloroethylene 0.007

(8) 71–55–6 1,1,1-Trichloroethane 0.2

(9) 156–59–2 cis-1,2-Dichloroethylene 0.07

(10) 78–87–5 1,2-Dichloropropane 0.005

(11) 100–41–4 Ethylbenzene 0.7

(12) 108–90–7 Monochlorobenzene 0.1

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(b) The Administrator, pursuant to section 1412 of the Act, hereby identifies as indicated in the Table 

below granular activated carbon (GAC), packed tower aeration (PTA), or oxidation (OX) as the best 

technology treatment technique, or other means available for achieving compliance with the maximum 

contaminant level for organic contaminants identified in paragraphs (a) and (c) of this section: 

BAT for Organic Contaminants Listed in §141.61 (a) and (c) 

(13) 95–50–1 o-Dichlorobenzene 0.6

(14) 100–42–5 Styrene 0.1

(15) 127–18–4 Tetrachloroethylene 0.005

(16) 108–88–3 Toluene 1

(17) 156–60–5 trans-1,2-Dichloroethylene 0.1

(18) 1330–20–7 Xylenes (total) 10

(19) 75–09–2 Dichloromethane 0.005

(20) 120–82–1 1,2,4-Trichloro- benzene .07

(21) 79–00–5 1,1,2-Trichloro- ethane .005

CAS No. Contaminant GAC PTA OX

15972–60–8 Alachlor X

116–06–3 Aldicarb X

1646–88–4 Aldicarb sulfone X

1646–87–3 Aldicarb sulfoxide X

1912–24–9 Atrazine X

71–43–2 Benzene X X

50–32–8 Benzo[a]pyrene X

1563–66–2 Carbofuran X

56–23–5 Carbon tetrachloride X X

57–74–9 Chlordane X

75–99–0 Dalapon X

94–75–7 2,4-D X

103–23–1 Di (2-ethylhexyl) adipate X X

117–81–7 Di (2-ethylhexyl) phthalate X

96–12–8 Dibromochloropropane (DBCP) X X

95–50–1 o-Dichlorobenzene X X

106–46–7 para-Dichlorobenzene X X

107–06–2 1,2-Dichloroethane X X

75–35–4 1,1-Dichloroethylene X X

156–59–2 cis-1,2-Dichloroethylene X X

156–60–5 trans-1,2-Dichloroethylene X X

75–09–2 Dichloromethane X

78–87–5 1,2-Dichloropropane X X

88–85–7 Dinoseb X

85–00–7 Diquat X

145–73–3 Endothall X

72–20–8 Endrin X

100–41–4 Ethylbenzene X X

106–93–4 Ethylene Dibromide (EDB) X X

1071–83–6 Gylphosate X

76–44–8 Heptachlor X

1024–57–3 Heptachlor epoxide X

118–74–1 Hexachlorobenzene X

77–47–3 Hexachlorocyclopentadiene X X

58–89–9 Lindane X

72–43–5 Methoxychlor X

108–90–7 Monochlorobenzene X X

23135–22–0 Oxamyl (Vydate) X

87–86–5 Pentachlorophenol X

1918–02–1 Picloram X

1336–36–3 Polychlorinated biphenyls (PCB) X

122–34–9 Simazine X

100–42–5 Styrene X X

1746–01–6 2,3,7,8-TCDD (Dioxin) X

127–18–4 Tetrachloroethylene X X

108–88–3 Toluene X X

8001–35–2 Toxaphene X

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(c) The following maximum contaminant levels for synthetic organic contaminants apply to community 

water systems and non-transient, non-community water systems: 

[56 FR 3593, Jan. 30, 1991, as amended at 56 FR 30280, July 1, 1991; 57 FR 31846, July 17, 1992; 59 

FR 34324, July 1, 1994] 

§ 141.62 Maximum contaminant levels for inorganic contaminants. 

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(a) [Reserved] 

(b) The maximum contaminant levels for inorganic contaminants specified in paragraphs (b) (2)–(6), (b)

(10), and (b) (11)–(16) of this section apply to community water systems and non-transient, noncommunity water systems. The maximum contaminant level specified in paragraph (b)(1) of this section 

only applies to community water systems. The maximum contaminant levels specified in (b)(7), (b)(8), 

and (b)(9) of this section apply to community water systems; non-transient, non-community water 

systems; and transient non-community water systems. 

93–72–1 2,4,5-TP (Silvex) X

120–82–1 1,2,4-Trichlorobenzene X X

71–55–6 1,1,1-Trichloroethane X X

79–00–5 1,1,2-Trichloroethane X X

79–01–6 Trichloroethylene X X

75–01–4 Vinyl chloride X

1330–20–7 Xylene X X

CAS No. Contaminant MCL (mg/l)

(1) 15972–60–8 Alachlor 0.002

(2) 116–06–3 Aldicarb 0.003

(3) 1646–87–3 Aldicarb sulfoxide 0.004

(4) 1646–87–4 Aldicarb sulfone 0.002

(5) 1912–24–9 Atrazine 0.003

(6) 1563–66–2 Carbofuran 0.04

(7) 57–74–9 Chlordane 0.002

(8) 96–12–8 Dibromochloropropane 0.0002

(9) 94–75–7 2,4-D 0.07

(10) 106–93–4 Ethylene dibromide 0.00005

(11) 76–44–8 Heptachlor 0.0004

(12) 1024–57–3 Heptachlor epoxide 0.0002

(13) 58–89–9 Lindane 0.0002

(14) 72–43–5 Methoxychlor 0.04

(15) 1336–36–3 Polychlorinated biphenyls 0.0005

(16) 87–86–5 Pentachlorophenol 0.001

(17) 8001–35–2 Toxaphene 0.003

(18) 93–72–1 2,4,5-TP 0.05

(19) 50–32–8 Benzo[a]pyrene 0.0002

(20) 75–99–0 Dalapon 0.2

(21) 103–23–1 Di(2-ethylhexyl) adipate 0.4

(22) 117–81–7 Di(2-ethylhexyl) phthalate 0.006

(23) 88–85–7 Dinoseb 0.007

(24) 85–00–7 Diquat 0.02

(25) 145–73–3 Endothall 0.1

(26) 72–20–8 Endrin 0.002

(27) 1071–53–6 Glyphosate 0.7

(28) 118–74–1 Hexacholorbenzene 0.001

(29) 77–47–4 Hexachlorocyclopentadiene 0.05

(30) 23135–22–0 Oxamyl (Vydate) 0.2

(31) 1918–02–1 Picloram 0.5

(32) 122–34–9 Simazine 0.004

(33) 1746–01–6 2,3,7,8-TCDD (Dioxin) 3×10−8

Contaminant MCL (mg/l)

(1) Fluoride 4.0

(2) Asbestos 7 Million Fibers/liter (longer than 10 μm).

(3) Barium 2

(4) Cadmium 0.005

(5) Chromium 0.1

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(c) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment technique, or other means available for achieving compliance with the maximum 

contaminant levels for inorganic contaminants identified in paragraph (b) of this section, except fluoride: 

BAT for Inorganic Compounds Listed in Section 141.62(b) 

1BAT only if influent Hg concentrations ≤10μg/1.

2BAT for Chromium III only.

3BAT for Selenium IV only.

4BATs for Arsenic V. Pre-oxidation may be required to convert Arsenic III to Arsenic V.

5To obtain high removals, iron to arsenic ratio must be at least 20:1.

Key to BATS in Table

1 = Activated Alumina 

2 = Coagulation/Filtration (not BAT for systems < 500 service connections) 

3 = Direct and Diatomite Filtration 

4 = Granular Activated Carbon 

5 = Ion Exchange 

6 = Lime Softening (not BAT for systems <500 service connections) 

7 = Reverse Osmosis 

8 = Corrosion Control 

9 = Electrodialysis 

10 = Chlorine 

11 = Ultraviolet 

12 = Oxidation/Filtration 

13 = Alkaline Chlorination (pH ≥8.5) 

(6) Mercury 0.002

(7) Nitrate 10 (as Nitrogen)

(8) Nitrite 1 (as Nitrogen)

(9) Total Nitrate and Nitrite 10 (as Nitrogen)

(10) Selenium 0.05

(11) Antimony 0.006

(12) Beryllium 0.004

(13) Cyanide (as free Cyanide) 0.2

(14) [Reserved]

(15) Thallium 0.002

(16) Arsenic 0.010

Chemical Name BAT(s)

Antimony 2,7

Arsenic4 1, 2, 5, 6, 7, 9, 125

Asbestos 2,3,8

Barium 5,6,7,9

Beryllium 1,2,5,6,7

Cadmium 2,5,6,7

Chromium 2,5,62,7

Cyanide 5,7,13

Mercury 21,4,61,71

Nickel 5,6,7

Nitrate 5,7,9

Nitrite 5,7

Selenium 1,23,6,7,9

Thallium 1,5

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(d) The Administrator, pursuant to section 1412 of the Act, hereby identifies in the following table the 

affordable technology, treatment technique, or other means available to systems serving 10,000 persons 

or fewer for achieving compliance with the maximum contaminant level for arsenic: 

Small System Compliance Technologies (SSCTs)1for Arsenic2

1Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs must be affordable and technically feasible for 

small systems. 

2SSCTs for Arsenic V. Pre-oxidation may be required to convert Arsenic III to Arsenic V.

3The Act (ibid.) specifies three categories of small systems: (i) those serving 25 or more, but fewer than 

501, (ii) those serving more than 500, but fewer than 3,301, and (iii) those serving more than 3,300, but 

fewer than 10,001. 

4When POU or POE devices are used for compliance, programs to ensure proper long-term operation, 

maintenance, and monitoring must be provided by the water system to ensure adequate performance. 

5Unlikely to be installed solely for arsenic removal. May require pH adjustment to optimal range if high 

removals are needed. 

6Technologies reject a large volume of water—may not be appropriate for areas where water quantity 

may be an issue. 

7To obtain high removals, iron to arsenic ratio must be at least 20:1.

[56 FR 3594, Jan. 30, 1991, as amended at 56 FR 30280, July 1, 1991; 57 FR 31847, July 17, 1992; 59 

FR 34325, July 1, 1994; 60 FR 33932, June 29, 1995; 66 FR 7063, Jan. 22, 2001; 68 FR 14506, Mar. 

25, 2003; 69 FR 38855, June 29, 2004] 

§ 141.63 Maximum contaminant levels (MCLs) for microbiological contaminants. 

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(a) The MCL is based on the presence or absence of total coliforms in a sample, rather than coliform 

density. 

(1) For a system which collects at least 40 samples per month, if no more than 5.0 percent of the 

samples collected during a month are total coliform-positive, the system is in compliance with the MCL 

for total coliforms. 

(2) For a system which collects fewer than 40 samples/month, if no more than one sample collected 

during a month is total coliform-positive, the system is in compliance with the MCL for total coliforms. 

(b) Any fecal coliform-positive repeat sample or E. coli -positive repeat sample, or any total coliformpositive repeat sample following a fecal coliform-positive or E. coli -positive routine sample constitutes a 

violation of the MCL for total coliforms. For purposes of the public notification requirements in subpart Q, 

this is a violation that may pose an acute risk to health. 

(c) A public water system must determine compliance with the MCL for total coliforms in paragraphs (a) 

and (b) of this section for each month in which it is required to monitor for total coliforms. 

(d) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

contaminant level for total coliforms in paragraphs (a) and (b) of this section: 

(1) Protection of wells from contamination by coliforms by appropriate placement and construction; 

(2) Maintenance of a disinfectant residual throughout the distribution system; 

(3) Proper maintenance of the distribution system including appropriate pipe replacement and repair 

procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, 

and continual maintenance of positive water pressure in all parts of the distribution system; 

(4) Filtration and/or disinfection of surface water, as described in subpart H, or disinfection of ground 

Small system compliance 

technology

Affordable for listed small system 

categories3

Activated Alumina (centralized) All size categories.

Activated Alumina (Point-of-Use)4 All size categories.

Coagulation/Filtration5 501–3,300, 3,301–10,000.

Coagulation-assisted Microfiltration 501–3,300, 3,301–10,000.

Electrodialysis reversal6 501–3,300, 3,301–10,000.

Enhanced coagulation/filtration All size categories

Enhanced lime softening (pH> 10.5) All size categories.

Ion Exchange All size categories.

Lime Softening5 501–3,300, 3,301–10,000.

Oxidation/Filtration7 All size categories.

Reverse Osmosis (centralized)6 501–3,300, 3,301–10,000.

Reverse Osmosis (Point-of-Use)4 All size categories.

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water using strong oxidants such as chlorine, chlorine dioxide, or ozone; and 

(5) For systems using ground water, compliance with the requirements of an EPA-approved State 

Wellhead Protection Program developed and implemented under section 1428 of the SDWA. 

[54 FR 27566, June 29, 1989; 55 FR 25064, June 19, 1990, as amended at 65 FR 26022, May 4, 2000] 

§ 141.64 Maximum contaminant levels for disinfection byproducts. 

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(a) Bromate and chlorite. The maximum contaminant levels (MCLs) for bromate and chlorite are as 

follows: 

(1) Compliance dates for CWSs and NTNCWSs. Subpart H systems serving 10,000 or more persons 

must comply with this paragraph (a) beginning January 1, 2002. Subpart H systems serving fewer than 

10,000 persons and systems using only ground water not under the direct influence of surface water 

must comply with this paragraph (a) beginning January 1, 2004. 

(2) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

contaminant levels for bromate and chlorite identified in this paragraph (a): 

(b) TTHM and HAA5. (1) Subpart L—RAA compliance. (i) Compliance dates. Subpart H systems serving 

10,000 or more persons must comply with this paragraph (b)(1) beginning January 1, 2002. Subpart H 

systems serving fewer than 10,000 persons and systems using only ground water not under the direct 

influence of surface water must comply with this paragraph (b)(1) beginning January 1, 2004. All 

systems must comply with these MCLs until the date specified for subpart V compliance in §141.620(c). 

(ii) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

contaminant levels for TTHM and HAA5 identified in this paragraph (b)(1): 

(2) Subpart V—LRAA compliance. (i) Compliance dates. The subpart V MCLs for TTHM and HAA5 must 

be complied with as a locational running annual average at each monitoring location beginning the date 

specified for subpart V compliance in §141.620(c). 

(ii) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

contaminant levels for TTHM and HAA5 identified in this paragraph (b)(2) for all systems that disinfect 

their source water: 

(iii) The Administrator, pursuant to section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

contaminant levels for TTHM and HAA5 identified in this paragraph (b)(2) for consecutive systems and 

applies only to the disinfected water that consecutive systems buy or otherwise receive: 

Disinfection byproduct MCL (mg/L)

Bromate 0.010

Chlorite 1.0

Disinfection 

byproduct Best available technology

Bromate Control of ozone treatment process to reduce production of 

bromate

Chlorite Control of treatment processes to reduce disinfectant 

demand and control of disinfection treatment processes to 

reduce disinfectant levels

Disinfection byproduct MCL (mg/L)

Total trihalomethanes (TTHM) 0.080

Haloacetic acids (five) (HAA5) 0.060

Disinfection byproduct Best available technology

Total trihalomethanes (TTHM) 

and Haloacetic acids (five) 

(HAA5)

Enhanced coagulation or enhanced 

softening or GAC10, with chlorine as the 

primary and residual disinfectant

Disinfection byproduct MCL (mg/L)

Total trihalomethanes (TTHM) 0.080

Haloacetic acids (five) (HAA5) 0.060

Disinfection byproduct Best available technology

Total trihalomethanes 

(TTHM) and Haloacetic acids 

(five) (HAA5)

Enhanced coagulation or enhanced softening, 

plus GAC10; or nanofiltration with a molecular 

weight cutoff ≤1000 Daltons; or GAC20

Disinfection byproduct Best available technology

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[71 FR 478, Jan. 4, 2006] 

§ 141.65 Maximum residual disinfectant levels. 

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(a) Maximum residual disinfectant levels (MRDLs) are as follows: 

(b) Compliance dates —(1) CWSs and NTNCWSs. Subpart H systems serving 10,000 or more persons 

must comply with this section beginning January 1, 2002. Subpart H systems serving fewer than 10,000 

persons and systems using only ground water not under the direct influence of surface water must 

comply with this subpart beginning January 1, 2004. 

(2) Transient NCWSs. Subpart H systems serving 10,000 or more persons and using chlorine dioxide as 

a disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning January 1, 2002. 

Subpart H systems serving fewer than 10,000 persons and using chlorine dioxide as a disinfectant or 

oxidant and systems using only ground water not under the direct influence of surface water and using 

chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning 

January 1, 2004. 

(c) The Administrator, pursuant to Section 1412 of the Act, hereby identifies the following as the best 

technology, treatment techniques, or other means available for achieving compliance with the maximum 

residual disinfectant levels identified in paragraph (a) of this section: control of treatment processes to 

reduce disinfectant demand and control of disinfection treatment processes to reduce disinfectant levels. 

[63 FR 69465, Dec. 16, 1998, as amended at 66 FR 3776, Jan. 16, 2001] 

§ 141.66 Maximum contaminant levels for radionuclides. 

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(a) [Reserved] 

(b) MCL for combined radium-226 and -228. The maximum contaminant level for combined radium-226 

and radium-228 is 5 pCi/L. The combined radium-226 and radium-228 value is determined by the 

addition of the results of the analysis for radium-226 and the analysis for radium-228. 

(c) MCL for gross alpha particle activity (excluding radon and uranium). The maximum contaminant level 

for gross alpha particle activity (including radium-226 but excluding radon and uranium) is 15 pCi/L. 

(d) MCL for beta particle and photon radioactivity. (1) The average annual concentration of beta particle 

and photon radioactivity from man-made radionuclides in drinking water must not produce an annual 

dose equivalent to the total body or any internal organ greater than 4 millirem/year (mrem/year). 

(2) Except for the radionuclides listed in table A, the concentration of man-made radionuclides causing 4 

mrem total body or organ dose equivalents must be calculated on the basis of 2 liter per day drinking 

water intake using the 168 hour data list in “Maximum Permissible Body Burdens and Maximum 

Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure,” NBS 

(National Bureau of Standards) Handbook 69 as amended August 1963, U.S. Department of Commerce. 

This incorporation by reference was approved by the Director of the Federal Register in accordance with 

5 U.S.C. 552(a) and 1 CFR part 51. Copies of this document are available from the National Technical 

Information Service, NTIS ADA 280 282, U.S. Department of Commerce, 5285 Port Royal Road, 

Springfield, Virginia 22161. The toll-free number is 800–553–6847. Copies may be inspected at EPA's 

Drinking Water Docket, 401 M Street, SW., Washington, DC 20460; or at the National Archives and 

Records Administration (NARA). For information on the availability of this material at NARA, call 202–

741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. If two or more 

radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ shall 

not exceed 4 mrem/year. 

Table A—Average Annual Concentrations Assumed To Produce: a Total Body or Organ Dose of 

4 mrem/yr 

(e) MCL for uranium. The maximum contaminant level for uranium is 30 μg/L. 

(f) Compliance dates. (1) Compliance dates for combined radium-226 and -228, gross alpha particle 

Total trihalomethanes 

(TTHM) and Haloacetic 

acids (five) (HAA5)

Systems serving ≥10,000: Improved distribution 

system and storage tank management to reduce 

residence time, plus the use of chloramines for 

disinfectant residual maintenance

 Systems serving <10,000: Improved distribution 

system and storage tank management to reduce 

residence time

Disinfectant residual MRDL (mg/L)

Chlorine 4.0 (as Cl2).

Chloramines 4.0 (as Cl2).

Chlorine dioxide 0.8 (as ClO2).

1. Radionuclide Critical organ pCi per liter

2. Tritium Total body 20,000

3. Strontium-90 Bone Marrow 8

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activity, gross beta particle and photon radioactivity, and uranium: Community water systems must 

comply with the MCLs listed in paragraphs (b), (c), (d), and (e) of this section beginning December 8, 

2003 and compliance shall be determined in accordance with the requirements of §§141.25 and 141.26. 

Compliance with reporting requirements for the radionuclides under appendix A to subpart O and 

appendices A and B to subpart Q is required on December 8, 2003. 

(2) [Reserved] 

(g) Best available technologies (BATs) for radionuclides. The Administrator, pursuant to section 1412 of 

the Act, hereby identifies as indicated in the following table the best technology available for achieving 

compliance with the maximum contaminant levels for combined radium-226 and -228, uranium, gross 

alpha particle activity, and beta particle and photon radioactivity. 

Table B—BAT for Combined Radium-226 and Radium-228, Uranium, Gross Alpha Particle 

Activity, and Beta Particle and Photon Radioactivity 

(h) Small systems compliance technologies list for radionuclides. 

Table C—List of Small Systems Compliance Technologies for Radionuclides and Limitations to 

Use 

1National Research Council (NRC). Safe Water from Every Tap: Improving Water Service to Small 

Communities. National Academy Press. Washington, D.C. 1997. 

2A POU, or “point-of-use” technology is a treatment device installed at a single tap used for the purpose 

of reducing contaminants in drinking water at that one tap. POU devices are typically installed at the 

kitchen tap. See the April 21, 2000 NODA for more details. 

 Limitations Footnotes: Technologies for Radionuclides: 

aThe regeneration solution contains high concentrations of the contaminant ions. Disposal options 

should be carefully considered before choosing this technology. 

bWhen POU devices are used for compliance, programs for long-term operation, maintenance, and 

monitoring must be provided by water utility to ensure proper performance. 

Contaminant BAT

1. Combined radium-226 and 

radium-228

Ion exchange, reverse osmosis, lime 

softening.

2. Uranium Ion exchange, reverse osmosis, lime 

softening, coagulation/filtration.

3. Gross alpha particle activity 

(excluding Radon and Uranium)

Reverse osmosis.

4. Beta particle and photon 

radioactivity

Ion exchange, reverse osmosis.

Unit technologies

Limitations 

(see 

footnotes)

Operator 

skill level 

required1

Raw water quality 

range and 

considerations.1

1. Ion exchange (IE) (

a) Intermediate All ground waters.

2. Point of use (POU2) IE (b) Basic All ground waters.

3. Reverse osmosis (RO) (

c) Advanced Surface waters 

usually require prefiltration.

4. POU2RO (b) Basic Surface waters 

usually require prefiltration.

5. Lime softening (

d) Advanced All waters.

6. Green sand filtration (

e) Basic.

7. Co-precipitation with 

Barium sulfate (

f

) Intermediate 

to Advanced

Ground waters with 

suitable water 

quality.

8. 

Electrodialysis/electrodialysis 

reversal

Basic to 

Intermediate

All ground waters.

9. Pre-formed hydrous 

Manganese oxide filtration (

g) Intermediate All ground waters.

10. Activated alumina (

a), (h) Advanced All ground waters; 

competing anion 

concentrations may 

affect regeneration 

frequency.

11. Enhanced 

coagulation/filtration (

i

) Advanced Can treat a wide 

range of water 

qualities.

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cReject water disposal options should be carefully considered before choosing this technology. See 

other RO limitations described in the SWTR Compliance Technologies Table. 

dThe combination of variable source water quality and the complexity of the water chemistry involved 

may make this technology too complex for small surface water systems. 

eRemoval efficiencies can vary depending on water quality.

f

This technology may be very limited in application to small systems. Since the process requires static 

mixing, detention basins, and filtration, it is most applicable to systems with sufficiently high sulfate 

levels that already have a suitable filtration treatment train in place. 

gThis technology is most applicable to small systems that already have filtration in place.

hHandling of chemicals required during regeneration and pH adjustment may be too difficult for small 

systems without an adequately trained operator. 

i

Assumes modification to a coagulation/filtration process already in place.

Table D—Compliance Technologies by System Size Category for Radionuclide NPDWR's 

Note:1Numbers correspond to those technologies found listed in the table C of 141.66(h).

[65 FR 76748, Dec. 7, 2000] 

Subpart H—Filtration and Disinfection 

 top

Source: 54 FR 27527, June 29, 1989, unless otherwise noted. 

§ 141.70 General requirements. 

 top

(a) The requirements of this subpart H constitute national primary drinking water regulations. These 

regulations establish criteria under which filtration is required as a treatment technique for public water 

systems supplied by a surface water source and public water systems supplied by a ground water 

source under the direct influence of surface water. In addition, these regulations establish treatment 

technique requirements in lieu of maximum contaminant levels for the following contaminants: Giardia 

lamblia, viruses, heterotrophic plate count bacteria, Legionella, and turbidity. Each public water system 

with a surface water source or a ground water source under the direct influence of surface water must 

provide treatment of that source water that complies with these treatment technique requirements. The 

treatment technique requirements consist of installing and properly operating water treatment processes 

which reliably achieve: 

(1) At least 99.9 percent (3-log) removal and/or inactivation of Giardia lamblia cysts between a point 

where the raw water is not subject to recontamination by surface water runoff and a point downstream 

before or at the first customer; and 

(2) At least 99.99 percent (4-log) removal and/or inactivation of viruses between a point where the raw 

water is not subject to recontamination by surface water runoff and a point downstream before or at the 

first customer. 

(b) A public water system using a surface water source or a ground water source under the direct 

influence of surface water is considered to be in compliance with the requirements of paragraph (a) of 

this section if: 

(1) It meets the requirements for avoiding filtration in §141.71 and the disinfection requirements in 

§141.72(a); or 

(2) It meets the filtration requirements in §141.73 and the disinfection requirements in §141.72(b). 

(c) Each public water system using a surface water source or a ground water source under the direct 

influence of surface water must be operated by qualified personnel who meet the requirements specified 

by the State. 

(d) Additional requirements for systems serving at least 10,000 people. In addition to complying with 

requirements in this subpart, systems serving at least 10,000 people must also comply with the 

requirements in subpart P of this part. 

Contaminant

Compliance technologies1for system 

size categories (population served) 3,300–

25–500 501–3,300 10,000

1. Combined radium226 and radium-2281, 2, 3, 4, 5, 6, 7, 

8, 9

1, 2, 3, 4, 5, 6, 7, 8, 

9

1, 2, 3, 4, 5, 

6, 7. 8, 9.

2. Gross alpha particle 

activity

3, 4 3, 4 3, 4.

3. Beta particle activity 

and photon activity

1, 2, 3, 4 1, 2, 3, 4 1, 2, 3, 4.

4. Uranium 1, 2, 4, 10, 11 1, 2, 3, 4, 5, 10, 11 1, 2, 3, 4, 5, 

10, 11.

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(e) Additional requirements for systems serving fewer than 10,000 people. In addition to complying with 

requirements in this subpart, systems serving fewer than 10,000 people must also comply with the 

requirements in subpart T of this part. 

[54 FR 27527, June 29, 1989, as amended at 63 FR 69516, Dec. 16, 1998; 67 FR 1836, Jan. 14, 2002] 

§ 141.71 Criteria for avoiding filtration. 

 top

A public water system that uses a surface water source must meet all of the conditions of paragraphs (a) 

and (b) of this section, and is subject to paragraph (c) of this section, beginning December 30, 1991, 

unless the State has determined, in writing pursuant to §1412(b)(7)(C)(iii), that filtration is required. A 

public water system that uses a ground water source under the direct influence of surface water must 

meet all of the conditions of paragraphs (a) and (b) of this section and is subject to paragraph (c) of this 

section, beginning 18 months after the State determines that it is under the direct influence of surface 

water, or December 30, 1991, whichever is later, unless the State has determined, in writing pursuant to 

§1412(b)(7)(C)(iii), that filtration is required. If the State determines in writing pursuant to §1412(b)(7)(C)

(iii) before December 30, 1991, that filtration is required, the system must have installed filtration and 

meet the criteria for filtered systems specified in §§141.72(b) and 141.73 by June 29, 1993. Within 18 

months of the failure of a system using surface water or a ground water source under the direct 

influence of surface water to meet any one of the requirements of paragraphs (a) and (b) of this section 

or after June 29, 1993, whichever is later, the system must have installed filtration and meet the criteria 

for filtered systems specified in §§141.72(b) and 141.73. 

(a) Source water quality conditions. (1) The fecal coliform concentration must be equal to or less than 

20/100 ml, or the total coliform concentration must be equal to or less than 100/100 ml (measured as 

specified in §141.74 (a) (1) and (2) and (b)(1)), in representative samples of the source water 

immediately prior to the first or only point of disinfectant application in at least 90 percent of the 

measurements made for the 6 previous months that the system served water to the public on an 

ongoing basis. If a system measures both fecal and total coliforms, the fecal coliform criterion, but not 

the total coliform criterion, in this paragraph must be met. 

(2) The turbidity level cannot exceed 5 NTU (measured as specified in §141.74 (a)(1) and (b)(2)) in 

representative samples of the source water immediately prior to the first or only point of disinfectant 

application unless: (i) the State determines that any such event was caused by circumstances that were 

unusual and unpredictable; and (ii) as a result of any such event, there have not been more than two 

events in the past 12 months the system served water to the public, or more than five events in the past 

120 months the system served water to the public, in which the turbidity level exceeded 5 NTU. An 

“event” is a series of consecutive days during which at least one turbidity measurement each day 

exceeds 5 NTU. 

(b) Site-specific conditions. (1)(i) The public water system must meet the requirements of §141.72(a)(1) 

at least 11 of the 12 previous months that the system served water to the public, on an ongoing basis, 

unless the system fails to meet the requirements during 2 of the 12 previous months that the system 

served water to the public, and the State determines that at least one of these failures was caused by 

circumstances that were unusual and unpredictable. 

(ii) The public water system must meet the requirements of §141.72(a)(2) at all times the system serves 

water to the public. 

(iii) The public water system must meet the requirements of §141.72(a)(3) at all times the system serves 

water to the public unless the State determines that any such failure was caused by circumstances that 

were unusual and unpredictable. 

(iv) The public water system must meet the requirements of §141.72(a)(4) on an ongoing basis unless 

the State determines that failure to meet these requirements was not caused by a deficiency in 

treatment of the source water. 

(2) The public water system must maintain a watershed control program which minimizes the potential 

for contamination by Giardia lamblia cysts and viruses in the source water. The State must determine 

whether the watershed control program is adequate to meet this goal. The adequacy of a program to 

limit potential contamination by Giardia lamblia cysts and viruses must be based on: the 

comprehensiveness of the watershed review; the effectiveness of the system's program to monitor and 

control detrimental activities occurring in the watershed; and the extent to which the water system has 

maximized land ownership and/or controlled land use within the watershed. At a minimum, the 

watershed control program must: 

(i) Characterize the watershed hydrology and land ownership; 

(ii) Identify watershed characteristics and activities which may have an adverse effect on source water 

quality; and 

(iii) Monitor the occurrence of activities which may have an adverse effect on source water quality. 

The public water system must demonstrate through ownership and/or written agreements with 

landowners within the watershed that it can control all human activities which may have an adverse 

impact on the microbiological quality of the source water. The public water system must submit an 

annual report to the State that identifies any special concerns about the watershed and how they are 

being handled; describes activities in the watershed that affect water quality; and projects what adverse 

activities are expected to occur in the future and describes how the public water system expects to 

address them. For systems using a ground water source under the direct influence of surface water, an 

approved wellhead protection program developed under section 1428 of the Safe Drinking Water Act 

may be used, if the State deems it appropriate, to meet these requirements. 

(3) The public water system must be subject to an annual on-site inspection to assess the watershed 

control program and disinfection treatment process. Either the State or a party approved by the State 

must conduct the on-site inspection. The inspection must be conducted by competent individuals such 

as sanitary and civil engineers, sanitarians, or technicians who have experience and knowledge about 

the operation and maintenance of a public water system, and who have a sound understanding of public 

health principles and waterborne diseases. A report of the on-site inspection summarizing all findings 

must be prepared every year. The on-site inspection must indicate to the State's satisfaction that the 

watershed control program and disinfection treatment process are adequately designed and maintained. 

The on-site inspection must include: 

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(i) A review of the effectiveness of the watershed control program; 

(ii) A review of the physical condition of the source intake and how well it is protected; 

(iii) A review of the system's equipment maintenance program to ensure there is low probability for 

failure of the disinfection process; 

(iv) An inspection of the disinfection equipment for physical deterioration; 

(v) A review of operating procedures; 

(vi) A review of data records to ensure that all required tests are being conducted and recorded and 

disinfection is effectively practiced; and 

(vii) Identification of any improvements which are needed in the equipment, system maintenance and 

operation, or data collection. 

(4) The public water system must not have been identified as a source of a waterborne disease 

outbreak, or if it has been so identified, the system must have been modified sufficiently to prevent 

another such occurrence, as determined by the State. 

(5) The public water system must comply with the maximum contaminant level (MCL) for total coliforms 

in §141.63 at least 11 months of the 12 previous months that the system served water to the public, on 

an ongoing basis, unless the State determines that failure to meet this requirement was not caused by a 

deficiency in treatment of the source water. 

(6) The public water system must comply with the requirements for trihalomethanes in §§141.12 and 

141.30 until December 31, 2001. After December 31, 2001, the system must comply with the 

requirements for total trihalomethanes, haloacetic acids (five), bromate, chlorite, chlorine, chloramines, 

and chlorine dioxide in subpart L of this part. 

(c) Treatment technique violations. (1) A system that (i) fails to meet any one of the criteria in 

paragraphs (a) and (b) of this section and/or which the State has determined that filtration is required, in 

writing pursuant to §1412(b)(7)(C)(iii), and (ii) fails to install filtration by the date specified in the 

introductory paragraph of this section is in violation of a treatment technique requirement. 

(2) A system that has not installed filtration is in violation of a treatment technique requirement if: 

(i) The turbidity level (measured as specified in §141.74(a)(1) and (b)(2)) in a representative sample of 

the source water immediately prior to the first or only point of disinfection application exceeds 5 NTU; or 

(ii) The system is identified as a source of a waterborne disease outbreak. 

[54 FR 27527, June 29, 1989, as amended at 63 FR 69516, Dec. 16, 1998; 66 FR 3776, Jan. 16, 2001; 

69 FR 38855, June 29, 2004] 

§ 141.72 Disinfection. 

 top

A public water system that uses a surface water source and does not provide filtration treatment must 

provide the disinfection treatment specified in paragraph (a) of this section beginning December 30, 

1991, unless the State determines that filtration is required in writing pursuant to §1412 (b)(7)(C)(iii). A 

public water system that uses a ground water source under the direct influence of surface water and 

does not provide filtration treatment must provide disinfection treatment specified in paragraph (a) of this 

section beginning December 30, 1991, or 18 months after the State determines that the ground water 

source is under the influence of surface water, whichever is later, unless the State has determined that 

filtration is required in writing pursuant to §1412(b)(7)(C)(iii). If the State has determined that filtration is 

required, the system must comply with any interim disinfection requirements the State deems necessary 

before filtration is installed. A system that uses a surface water source that provides filtration treatment 

must provide the disinfection treatment specified in paragraph (b) of this section beginnng June 29, 

1993, or beginning when filtration is installed, whichever is later. A system that uses a ground water 

source under the direct influence of surface water and provides filtration treatment must provide 

disinfection treatment as specified in paragraph (b) of this section by June 29, 1993, or beginning when 

filtration is installed, whichever is later. Failure to meet any requirement of this section after the 

applicable date specified in this introductory paragraph is a treatment technique violation. 

(a) Disinfection requirements for public water systems that do not provide filtration. Each public water 

system that does not provide filtration treatment must provide disinfection treatment as follows: 

(1) The disinfection treatment must be sufficient to ensure at least 99.9 percent (3-log) inactivation of 

Giardia lamblia cysts and 99.99 percent (4-log) inactivation of viruses, every day the system serves 

water to the public, except any one day each month. Each day a system serves water to the public, the 

public water system must calculate the CT value(s) from the system's treatment parameters, using the 

procedure specified in §141.74(b)(3), and determine whether this value(s) is sufficient to achieve the 

specified inactivation rates for Giardia lamblia cysts and viruses. If a system uses a disinfectant other 

than chlorine, the system may demonstrate to the State, through the use of a State-approved protocol 

for on-site disinfection challenge studies or other information satisfactory to the State, that CT99.9values 

other than those specified in tables 2.1 and 3.1 in §141.74(b)(3) or other operational parameters are 

adequate to demonstrate that the system is achieving minimum inactivation rates required by paragraph 

(a)(1) of this section. 

(2) The disinfection system must have either (i) redundant components, including an auxiliary power 

supply with automatic start-up and alarm to ensure that disinfectant application is maintained 

continuously while water is being delivered to the distribution system, or (ii) automatic shut-off of delivery 

of water to the distribution system whenever there is less than 0.2 mg/l of residual disinfectant 

concentration in the water. If the State determines that automatic shut-off would cause unreasonable risk 

to health or interfere with fire protection, the system must comply with paragraph (a)(2)(i) of this section. 

(3) The residual disinfectant concentration in the water entering the distribution system, measured as 

specified in §141.74 (a)(2) and (b)(5), cannot be less than 0.2 mg/l for more than 4 hours. 

(4)(i) The residual disinfectant concentration in the distribution system, measured as total chlorine, 

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combined chlorine, or chlorine dioxide, as specified in §141.74 (a)(2) and (b)(6), cannot be undetectable 

in more than 5 percent of the samples each month, for any two consecutive months that the system 

serves water to the public. Water in the distribution system with a heterotrophic bacteria concentration 

less than or equal to 500/ml, measured as heterotrophic plate count (HPC) as specified in §141.74(a)(1), 

is deemed to have a detectable disinfectant residual for purposes of determining compliance with this 

requirement. Thus, the value “V” in the following formula cannot exceed 5 percent in one month, for any 

two consecutive months. 

where: 

a=number of instances where the residual disinfectant concentration is measured; 

b=number of instances where the residual disinfectant concentration is not measured but 

heterotrophic bacteria plate count (HPC) is measured; 

c=number of instances where the residual disinfectant concentration is measured but not 

detected and no HPC is measured; 

d=number of instances where the residual disinfectant concentration is measured but not 

detected and where the HPC is >500/ml; and 

e=number of instances where the residual disinfectant concentration is not measured and 

HPC is >500/ml. 

(ii) If the State determines, based on site-specific considerations, that a system has no means for having 

a sample transported and analyzed for HPC by a certified laboratory under the requisite time and 

temperature conditions specified by §141.74(a)(1) and that the system is providing adequate disinfection 

in the distribution system, the requirements of paragraph (a)(4)(i) of this section do not apply to that 

system. 

(b) Disinfection requirements for public water systems which provide filtration. Each public water system 

that provides filtration treatment must provide disinfection treatment as follows. 

(1) The disinfection treatment must be sufficient to ensure that the total treatment processes of that 

system achieve at least 99.9 percent (3-log) inactivation and/or removal of Giardia lamblia cysts and at 

least 99.99 percent (4-log) inactivation and/or removal of viruses, as determined by the State. 

(2) The residual disinfectant concentration in the water entering the distribution system, measured as 

specified in §141.74 (a)(2) and (c)(2), cannot be less than 0.2 mg/l for more than 4 hours. 

(3)(i) The residual disinfectant concentration in the distribution system, measured as total chlorine, 

combined chlorine, or chlorine dioxide, as specified in §141.74 (a)(2) and (c)(3), cannot be undetectable 

in more than 5 percent of the samples each month, for any two consecutive months that the system 

serves water to the public. Water in the distribution system with a heterotrophic bacteria concentration 

less than or equal to 500/ml, measured as heterotrophic plate count (HPC) as specified in §141.74(a)(1), 

is deemed to have a detectable disinfectant residual for purposes of determining compliance with this 

requirement. Thus, the value “V” in the following formula cannot exceed 5 percent in one month, for any 

two consecutive months. 

where: 

a=number of instances where the residual disinfectant concentration is measured; 

b=number of instances where the residual disinfectant concentration is not measured but 

heterotrophic bacteria plate count (HPC) is measured; 

c=number of instances where the residual disinfectant concentration is measured but not 

detected and no HPC is measured; 

d=number of instances where no residual disinfectant concentration is detected and where 

the HPC is >500/ml; and 

e=number of instances where the residual disinfectant concentration is not measured and 

HPC is >500/ml. 

(ii) If the State determines, based on site-specific considerations, that a system has no means for having 

a sample transported and analyzed for HPC by a certified laboratory under the requisite time and 

temperature conditions specified in §141.74(a)(1) and that the system is providing adequate disinfection 

in the distribution system, the requirements of paragraph (b)(3)(i) of this section do not apply. 

[54 FR 27527, June 29, 1989, as amended at 69 FR 38855, June 29, 2004] 

§ 141.73 Filtration. 

 top

A public water system that uses a surface water source or a ground water source under the direct 

influence of surface water, and does not meet all of the criteria in §141.71 (a) and (b) for avoiding 

filtration, must provide treatment consisting of both disinfection, as specified in §141.72(b), and filtration 

treatment which complies with the requirements of paragraph (a), (b), (c), (d), or (e) of this section by 

June 29, 1993, or within 18 months of the failure to meet any one of the criteria for avoiding filtration in 

§141.71 (a) and (b), whichever is later. Failure to meet any requirement of this section after the date 

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specified in this introductory paragraph is a treatment technique violation. 

(a) Conventional filtration treatment or direct filtration. (1) For systems using conventional filtration or 

direct filtration, the turbidity level of representative samples of a system's filtered water must be less than 

or equal to 0.5 NTU in at least 95 percent of the measurements taken each month, measured as 

specified in §141.74 (a)(1) and (c)(1), except that if the State determines that the system is capable of 

achieving at least 99.9 percent removal and/or inactivation of Giardia lamblia cysts at some turbidity 

level higher than 0.5 NTU in at least 95 percent of the measurements taken each month, the State may 

substitute this higher turbidity limit for that system. However, in no case may the State approve a 

turbidity limit that allows more than 1 NTU in more than 5 percent of the samples taken each month, 

measured as specified in §141.74 (a)(1) and (c)(1). 

(2) The turbidity level of representative samples of a system's filtered water must at no time exceed 5 

NTU, measured as specified in §141.74 (a)(1) and (c)(1). 

(3) Beginning January 1, 2002, systems serving at least 10,000 people must meet the turbidity 

requirements in §141.173(a). 

(4) Beginning January 1, 2005, systems serving fewer than 10,000 people must meet the turbidity 

requirements in §§141.550 through 141.553. 

(b) Slow sand filtration. (1) For systems using slow sand filtration, the turbidity level of representative 

samples of a system's filtered water must be less than or equal to 1 NTU in at least 95 percent of the 

measurements taken each month, measured as specified in §141.74 (a)(1) and (c)(1), except that if the 

State determines there is no significant interference with disinfection at a higher turbidity level, the State 

may substitute this higher turbidity limit for that system. 

(2) The turbidity level of representative samples of a system's filtered water must at no time exceed 5 

NTU, measured as specified in §141.74 (a)(1) and (c)(1). 

(c) Diatomaceous earth filtration. (1) For systems using diatomaceous earth filtration, the turbidity level 

of representative samples of a system's filtered water must be less than or equal to 1 NTU in at least 95 

percent of the measurements taken each month, measured as specified in §141.74 (a)(1) and (c)(1). 

(2) The turbidity level of representative samples of a system's filtered water must at no time exceed 5 

NTU, measured as specified in §141.74 (a)(1) and (c)(1). 

(d) Other filtration technologies. A public water system may use a filtration technology not listed in 

paragraphs (a) through (c) of this section if it demonstrates to the State, using pilot plant studies or other 

means, that the alternative filtration technology, in combination with disinfection treatment that meets the 

requirements of §141.72(b), consistently achieves 99.9 percent removal and/or inactivation of Giardia 

lamblia cysts and 99.99 percent removal and/or inactivation of viruses. For a system that makes this 

demonstration, the requirements of paragraph (b) of this section apply. Beginning January 1, 2002, 

systems serving at least 10,000 people must meet the requirements for other filtration technologies in 

§141.173(b). Beginning January 14, 2005, systems serving fewer than 10,000 people must meet the 

requirements for other filtration technologies in §141.550 through 141.553. 

[54 FR 27527, June 29, 1989, as amended at 63 FR 69516, Dec. 16, 1998; 66 FR 3776, Jan. 16, 2001; 

67 FR 1836, Jan. 14, 2002; 69 FR 38855, June 29, 2004] 

§ 141.74 Analytical and monitoring requirements. 

 top

(a) Analytical requirements. Only the analytical method(s) specified in this paragraph, or otherwise 

approved by EPA, may be used to demonstrate compliance with §§141.71, 141.72 and 141.73. 

Measurements for pH, turbidity, temperature and residual disinfectant concentrations must be conducted 

by a person approved by the State. Measurement for total coliforms, fecal coliforms and HPC must be 

conducted by a laboratory certified by the State or EPA to do such analysis. Until laboratory certification 

criteria are developed for the analysis of fecal coliforms and HPC, any laboratory certified for total 

coliforms analysis by the State or EPA is deemed certified for fecal coliforms and HPC analysis. The 

following procedures shall be conducted in accordance with the publications listed in the following 

section. This incorporation by reference was approved by the Director of the Federal Register in 

accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the methods published in Standard 

Methods for the Examination of Water and Wastewater may be obtained from the American Public 

Health Association et al., 1015 Fifteenth Street, NW., Washington, DC 20005; copies of the Minimal 

Medium ONPG-MUG Method as set forth in the article “National Field Evaluation of a Defined Substrate 

Method for the Simultaneous Enumeration of Total Coliforms and Esherichia coli from Drinking Water: 

Comparison with the Standard Multiple Tube Fermentation Method” (Edberg et al.), Applied and 

Environmental Microbiology, Volume 54, pp. 1595–1601, June 1988 (as amended under Erratum, 

Applied and Environmental Microbiology, Volume 54, p. 3197, December, 1988), may be obtained from 

the American Water Works Association Research Foundation, 6666 West Quincy Avenue, Denver, 

Colorado, 80235; and copies of the Indigo Method as set forth in the article “Determination of Ozone in 

Water by the Indigo Method” (Bader and Hoigne), may be obtained from Ozone Science & Engineering, 

Pergamon Press Ltd., Fairview Park, Elmsford, New York 10523. Copies may be inspected at the U.S. 

Environmental Protection Agency, Room EB15, 401 M St., SW., Washington, DC 20460 or at the 

National Archives and Records Administration (NARA). For information on the availability of this material 

at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

(1) Public water systems must conduct analysis of pH and temperature in accordance with one of the 

methods listed at §141.23(k)(1). Public water systems must conduct analysis of total coliforms, fecal 

coliforms, heterotrophic bacteria, and turbidity in accordance with one of the following analytical methods 

or one of the alternative methods listed in appendix A to subpart C of this part and by using analytical 

test procedures contained in Technical Notes on Drinking Water Methods, EPA–600/R–94–173, October 

1994. This document is available from the National Service Center for Environmental Publications 

(NSCEP), P.O. Box 42419, Cincinnati, OH 45242–0419 or http://www.epa.gov/nscep/ . 

Organism Methodology Citation1

Total Coliform2 Total Coliform Fermentation 

Technique3,4,5

9221 A, B, 

C

 Total Coliform Membrane Filter 9222 A, B, 

C

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The procedures shall be done in accordance with the documents listed below. The incorporation by 

reference of the following documents listed in footnotes 1, 6, 7 and 9–12 was approved by the Director 

of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the documents 

may be obtained from the sources listed below. Information regarding obtaining these documents can be 

obtained from the Safe Drinking Water Hotline at 800–426–4791. Documents may be inspected at 

EPA's Drinking Water Docket, 1301 Constitution Avenue, NW., EPA West, Room B102, Washington DC 

20460 (Telephone: 202–566–2426); or at the National Archives and Records Administration (NARA). 

For information on the availability of this material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

1Except where noted, all methods refer to Standard Methods for the Examination of Water and 

Wastewater, 18th edition (1992), 19th edition (1995), or 20th edition (1998), American Public Health 

Association, 1015 Fifteenth Street, NW., Washington, DC 20005. The cited methods published in any of 

these three editions may be used. In addition, the following online versions may also be used: 2130 B–

01, 9215 B–00, 9221 A, B, C, E–99, 9222 A, B, C, D–97, and 9223 B–97. Standard Methods Online are 

available at http://www.standardmethods.org. The year in which each method was approved by the 

Standard Methods Committee is designated by the last two digits in the method number. The methods 

listed are the only Online versions that may be used. 

2The time from sample collection to initiation of analysis may not exceed 8 hours. Systems must hold 

samples below 10 deg. C during transit. 

3Lactose broth, as commercially available, may be used in lieu of lauryl tryptose broth, if the system 

conducts at least 25 parallel tests between this medium and lauryl tryptose broth using the water 

normally tested, and this comparison demonstrates that the false-positive rate and false-negative rate for 

total coliform, using lactose broth, is less than 10 percent. 

4Media should cover inverted tubes at least one-half to two-thirds after the sample is added.

5No requirement exists to run the completed phase on 10 percent of all total coliform-positive confirmed 

tubes. 

6MI agar also may be used. Preparation and use of MI agar is set forth in the article, “New medium for 

the simultaneous detection of total coliform and Escherichia coli in water” by Brenner, K.P., et. al., 1993, 

Appl. Environ. Microbiol. 59:3534–3544. Also available from the Office of Water Resource Center (RC–

4100T), 1200 Pennsylvania Avenue, NW., Washington DC 20460, EPA/600/J–99/225. Verification of 

colonies is not required. 

7The ONPG-MUG Test is also known as the Autoanalysis Colilert System.

8A–1 broth may be held up to 7 days in a tightly closed screw cap tube at 4 °C.

9“Methods for the Determination of Inorganic Substances in Environmental Samples”, EPA/600/R–

93/100, August 1993. Available at NTIS, PB94–121811. 

10GLI Method 2, “Turbidity,” November 2, 1992, Great Lakes Instruments, Inc., 8855 North 55th Street, 

Milwaukee, WI 53223. 

11A description of the SimPlate method, “IDEXX SimPlate TM HPC Test Method for Heterotrophs in 

Water,” November 2000, can be obtained from IDEXX Laboratories, Inc., 1 IDEXX Drive, Westbrook, 

ME 04092, telephone (800) 321–0207. 

12A description of the Hach FilterTrak Method 10133, “Determination of Turbidity by Laser 

Nephelometry,” January 2000, Revision 2.0, can be obtained from; Hach Co., P.O. Box 389, Loveland, 

CO 80539–0389, telephone: 800–227–4224. 

13Styrene divinyl benzene beads (e.g., AMCO-AEPA–1 or equivalent) and stabilized formazin (e.g., 

Hach StablCalTMor equivalent) are acceptable substitutes for formazin.

(2) Public water systems must measure residual disinfectant concentrations with one of the analytical 

methods in the following table or one of the alternative methods listed in appendix A to subpart C of this 

part. If approved by the State, residual disinfectant concentrations for free chlorine and combined 

chlorine also may be measured by using DPD colorimetric test kits. In addition States may approve the 

use of the ITS free chlorine test strip for the determination of free chlorine. Use of the test strips is 

described in Method D99–003, “Free Chlorine Species (HOCl−and OCl−) by Test Strip,” Revision 3.0, 

November 21, 2003, available from Industrial Test Systems, Inc., 1875 Langston St., Rock Hill, SC 

29730. Free and total chlorine residuals may be measured continuously by adapting a specified chlorine 

residual method for use with a continuous monitoring instrument provided the chemistry, accuracy, and 

precision remain the same. Instruments used for continuous monitoring must be calibrated with a grab 

sample measurement at least every five days, or with a protocol approved by the State. 

Technique6

 ONPG-MUG Test7 9223

Fecal Coliforms2 Fecal Coliform Procedure8 9221 E

 Fecal Coliform Filter Procedure 9222 D

Heterotrophic 

bacteria2

Pour Plate Method 9215 B

 SimPlate11

Turbidity13 Nephelometric Method 2130 B

 Nephelometric Method 180.19

 Great Lakes Instruments Method 210

 Hach FilterTrak 1013312

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1All the listed methods are contained in the 18th, 19th, and 20th editions of Standard Methods for the 

Examination of Water and Wastewater, 1992, 1995, and 1998; the cited methods published in any of 

these three editions may be used. 

2Standard Methods Online are available at http://www.standardmethods.org. The year in which each 

method was approved by the Standard Methods Committee is designated by the last two digits in the 

method number. The methods listed are the only Online versions that may be used. 

3 Annual Book of ASTM Standards, Vol. 11.01, 2004 ; ASTM International; any year containing the cited 

version of the method may be used. Copies of this method may be obtained from ASTM International, 

100 Barr Harbor Drive, P.O. Box C700 West Conshohocken, PA 19428–2959. 

4EPA Method 327.0, Revision 1.1, “Determination of Chlorine Dioxide and Chlorite Ion in Drinking Water 

Using Lissamine Green B and Horseradish Peroxidase with Detection by Visible Spectrophotometry,” 

USEPA, May 2005, EPA 815–R–05–008. Available online at 

http://www.epa.gov/safewater/methods/sourcalt.html. 

(b) Monitoring requirements for systems that do not provide filtration. A public water system that uses a 

surface water source and does not provide filtration treatment must begin monitoring, as specified in this 

paragraph (b), beginning December 31, 1990, unless the State has determined that filtration is required 

in writing pursuant to §1412(b)(7)(C)(iii), in which case the State may specify alternative monitoring 

requirements, as appropriate, until filtration is in place. A public water system that uses a ground water 

source under the direct influence of surface water and does not provide filtration treatment must begin 

monitoring as specified in this paragraph (b) beginning December 31, 1990, or 6 months after the State 

determines that the ground water source is under the direct influence of surface water, whichever is 

later, unless the State has determined that filtration is required in writing pursuant to §1412(b)(7)(C)(iii), 

in which case the State may specify alternative monitoring requirements, as appropriate, until filtration is 

in place. 

(1) Fecal coliform or total coliform density measurements as required by §141.71(a)(1) must be 

performed on representative source water samples immediately prior to the first or only point of 

disinfectant application. The system must sample for fecal or total coliforms at the following minimum 

frequency each week the system serves water to the public: 

1Must be taken on separate days.

Also, one fecal or total coliform density measurement must be made every day the system serves water 

to the public and the turbidity of the source water exceeds 1 NTU (these samples count towards the 

weekly coliform sampling requirement) unless the State determines that the system, for logistical 

Residual Methodology SM1

SM 

Online2 Other

Free 

Chlorine

Amperometric Titration 4500–Cl 

D

4500–Cl 

D–00

D1253–033

 DPD Ferrous Titrimetric 4500–Cl 

F

4500–Cl 

F–00

 DPD Colorimetric 4500–Cl 

G

4500–Cl 

G–00

 Syringaldazine (FACTS) 4500–Cl 

H

4500–Cl 

H–00

Total 

Chlorine

Amperometric Titration 4500–Cl 

D

4500–Cl 

D–00

D1253–033

 Amperometric Titration (low 

level measurement)

4500–Cl 

E

4500–Cl 

E–00

 DPD Ferrous Titrimetric 4500–Cl 

F

4500–Cl 

F–00

 DPD Colorimetric 4500–Cl 

G

4500–Cl 

G–00

 Iodometric Electrode 4500–Cl 

I

4500–Cl I–

00

Chlorine 

Dioxide

Amperometric Titration 4500–

ClO2 C

4500–ClO2 

C–00

 DPD Method 4500–

ClO2 D

 Amperometric Titration 4500–

ClO2 E

4500–ClO2 

E–00

 Spectrophotometric 327.0, 

Revision 

1.14

Ozone Indigo Method 4500–

O3 B

4500–O3 

B–97

System size (persons served) Samples/week1

≤500 1

501 to 3,300 2

3,301 to 10,000 3

10,001 to 25,000 4

>25,000 5

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reasons outside the system's control, cannot have the sample analyzed within 30 hours of collection. 

(2) Turbidity measurements as required by §141.71(a)(2) must be performed on representative grab 

samples of source water immediately prior to the first or only point of disinfectant application every four 

hours (or more frequently) that the system serves water to the public. A public water system may 

substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous 

measurement for accuracy on a regular basis using a protocol approved by the State. 

(3) The total inactivation ratio for each day that the system is in operation must be determined based on 

the CT99.9values in tables 1.1–1.6, 2.1, and 3.1 of this section, as appropriate. The parameters 

necessary to determine the total inactivation ratio must be monitored as follows: 

(i) The temperature of the disinfected water must be measured at least once per day at each residual 

disinfectant concentration sampling point. 

(ii) If the system uses chlorine, the pH of the disinfected water must be measured at least once per day 

at each chlorine residual disinfectant concentration sampling point. 

(iii) The disinfectant contact time(s) (“T”) must be determined for each day during peak hourly flow. 

(iv) The residual disinfectant concentration(s) (“C”) of the water before or at the first customer must be 

measured each day during peak hourly flow. 

(v) If a system uses a disinfectant other than chlorine, the system may demonstrate to the State, through 

the use of a State-approved protocol for on-site disinfection challenge studies or other information 

satisfactory to the State, that CT99.9values other than those specified in tables 2.1 and 3.1 in this section 

other operational parameters are adequate to demonstrate that the system is achieving the minimum 

inactivation rates required by §141.72(a)(1). 

Table 1.1—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 0.5 °C or Lower1

1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature and at the higher pH. 

Table 1.2—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 5.0 °C1

Residual (mg/l)

pH

≤6.0 6.5 7.0 7.5 8.0 8.5 ≤9.0

≤0.4 137 163 195 237 277 329 390

0.6 141 168 200 239 286 342 407

0.8 145 172 205 246 295 354 422

1.0 148 176 210 253 304 365 437

1.2 152 180 215 259 313 376 451

1.4 155 184 221 266 321 387 464

1.6 157 189 226 273 329 397 477

1.8 162 193 231 279 338 407 489

2.0 165 197 236 286 346 417 500

2.2 169 201 242 297 353 426 511

2.4 172 205 247 298 361 435 522

2.6 175 209 252 304 368 444 533

2.8 178 213 257 310 375 452 543

3.0 181 217 261 316 382 460 552

Free residual (mg/l)

pH

≤6.0 6.5 7.0 7.5 8.0 8.5 ≤9.0

≤0.4 97 117 139 166 198 236 279

0.6 100 120 143 171 204 244 291

0.8 103 122 146 175 210 252 301

1.0 105 125 149 179 216 260 312

1.2 107 127 152 183 221 267 320

1.4 109 130 155 187 227 274 329

1.6 111 132 158 192 232 281 337

1.8 114 135 162 196 238 287 345

2.0 116 138 165 200 243 294 353

2.2 118 140 169 204 248 300 361

2.4 120 143 172 209 253 306 368

2.6 122 146 175 213 258 312 375

2.8 124 148 178 217 263 318 382

3.0 126 151 182 221 268 324 389

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1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature, and at the higher pH. 

Table 1.3—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 10.0 °C1

1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature, and at the higher pH. 

Table 1.4—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 15.0 °C1

1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature, and at the higher pH. 

Table 1.5—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 20°C1

Free residual (mg/l)

pH

≤6.0 6.5 7.0 7.5 8.0 8.5 ≤9.0

≤0.4 73 88 104 125 149 177 209

0.6 75 90 107 128 153 183 218

0.8 78 92 110 131 158 189 226

1.0 79 94 112 134 162 195 234

1.2 80 95 114 137 166 200 240

1.4 82 98 116 140 170 206 247

1.6 83 99 119 144 174 211 253

1.8 86 101 122 147 179 215 259

2.0 87 104 124 150 182 221 265

2.2 89 105 127 153 186 225 271

2.4 90 107 129 157 190 230 276

2.6 92 110 131 160 194 234 281

2.8 93 111 134 163 197 239 287

3.0 95 113 137 166 201 243 292

Free residual (mg/l)

pH

≤6.0 6.5 7.0 7.5 8.0 8.5 ≤9.0

≤0.4 49 59 70 83 99 118 140

0.6 50 60 72 86 102 122 146

0.8 52 61 73 88 105 126 151

1.0 53 63 75 90 108 130 156

1.2 54 64 76 92 111 134 160

1.4 55 65 78 94 114 137 165

1.6 56 66 79 96 116 141 169

1.8 57 68 81 98 119 144 173

2.0 58 69 83 100 122 147 177

2.2 59 70 85 102 124 150 181

2.4 60 72 86 105 127 153 184

2.6 61 73 88 107 129 156 188

2.8 62 74 89 109 132 159 191

3.0 63 76 91 111 134 162 195

Free residual (mg/l)

pH

≤ 6.0 6.5 7.0 7.5 8.0 8.5 ≤ 9.0

≤ 0.4 36 44 52 62 74 89 105

0.6 38 45 54 64 77 92 109

0.8 39 46 55 66 79 95 113

1.0 39 47 56 67 81 98 117

1.2 40 48 57 69 83 100 120

1.4 41 49 58 70 85 103 123

1.6 42 50 59 72 87 105 126

1.8 43 51 61 74 89 108 129

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1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature, and at the higher pH. 

Table 1.6—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Free 

Chlorine at 25°C1and Higher

1These CT values achieve greater than a 99.99 percent inactivation of viruses. CT values between the 

indicated pH values may be determined by linear interpolation. CT values between the indicated 

temperatures of different tables may be determined by linear interpolation. If no interpolation is used, 

use the CT99.9value at the lower temperature, and at the higher pH. 

Table 2.1—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by Chlorine 

Dioxide and Ozone1

1These CT values achieve greater than 99.99 percent inactivation of viruses. CT values between the 

indicated temperatures may be determined by linear interpolation. If no interpolation is used, use the 

CT99.9value at the lower temperature for determining CT99.9values between indicated temperatures. 

Table 3.1—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts By 

Chloramines1

1These values are for pH values of 6 to 9. These CT values may be assumed to achieve greater than 

99.99 percent inactivation of viruses only if chlorine is added and mixed in the water prior to the addition 

of ammonia. If this condition is not met, the system must demonstrate, based on on-site studies or other 

information, as approved by the State, that the system is achieving at least 99.99 percent inactivation of 

viruses. CT values between the indicated temperatures may be determined by linear interpolation. If no 

interpolation is used, use the CT99.9value at the lower temperature for determining CT99.9values 

between indicated temperatures. 

(4) The total inactivation ratio must be calculated as follows: 

(i) If the system uses only one point of disinfectant application, the system may determine the total 

inactivation ratio based on either of the following two methods: 

(A) One inactivation ratio (CTcalc/CT99.9) is determined before or at the first customer during peak 

hourly flow and if the CTcalc/CT99.9≥ 1.0, the 99.9 percent Giardia lamblia inactivation requirement has 

been achieved; or 

2.0 44 52 62 75 91 110 132

2.2 44 53 63 77 93 113 135

2.4 45 54 65 78 95 115 138

2.6 46 55 66 80 97 117 141

2.8 47 56 67 81 99 119 143

3.0 47 57 68 83 101 122 146

Free residual (mg/l)

pH

≤ 6.0 6.5 7.0 7.5 8.0 8.5 ≤ 9.0

≤ 0.4 24 29 35 42 50 59 70

0.6 25 30 36 43 51 61 73

0.8 26 31 37 44 53 63 75

1.0 26 31 37 45 54 65 78

1.2 27 32 38 46 55 67 80

1.4 27 33 39 47 57 69 82

1.6 28 33 40 48 58 70 84

1.8 29 34 41 49 60 72 86

2.0 29 35 41 50 61 74 88

2.2 30 35 42 51 62 75 90

2.4 30 36 43 52 63 77 92

2.6 31 37 44 53 65 78 94

2.8 31 37 45 54 66 80 96

3.0 32 38 46 55 67 81 97

 

Temperature

< 1°C 5°C 10°C 15°C 20°C ≥ 25°C

Chlorine dioxide 63 26 23 19 15 11

Ozone 2.9 1.9 1.4 0.95 0.72 0.48

Temperature

< 1 °C 5 °C 10 °C 15 °C 20 °C 25 °C

3,800 2,200 1,850 1,500 1,100 750

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(B) Successive CTcalc/CT99.9values, representing sequential inactivation ratios, are determined 

between the point of disinfectant application and a point before or at the first customer during peak 

hourly flow. Under this alternative, the following method must be used to calculate the total inactivation 

ratio: 

lamblia inactivation requirement has been achieved. 

(ii) If the system uses more than one point of disinfectant application before or at the first customer, the 

system must determine the CT value of each disinfection sequence immediately prior to the next point of 

disinfectant application during peak hourly flow. The CTcalc/CT99.9value of each sequence and 

must be calculated using the method in paragraph (b)(4)(i)(B) of this section to determine if the system is 

in compliance with §141.72(a). 

(iii) Although not required, the total percent inactivation for a system with one or more points of residual 

disinfectant concentration monitoring may be calculated by solving the following equation: 

(5) The residual disinfectant concentration of the water entering the distribution system must be 

monitored continuously, and the lowest value must be recorded each day, except that if there is a failure 

in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of 

continuous monitoring, but for no more than 5 working days following the failure of the equipment, and 

systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous 

monitoring on an ongoing basis at the frequencies prescribed below: 

1The day's samples cannot be taken at the same time. The sampling intervals are subject to State 

review and approval. 

If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling 

in lieu of continuous monitoring, the system must take a grab sample every 4 hours until the residual 

concentration is equal to or greater than 0.2 mg/l. 

(6)(i) The residual disinfectant concentration must be measured at least at the same points in the 

distribution system and at the same time as total coliforms are sampled, as specified in §141.21, except 

that the State may allow a public water system which uses both a surface water source or a ground 

water source under direct influence of surface water, and a ground water source, to take disinfectant 

residual samples at points other than the total coliform sampling points if the State determines that such 

points are more representative of treated (disinfected) water quality within the distribution system. 

Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in paragraph (a)(3) of 

this section, may be measured in lieu of residual disinfectant concentration. 

(ii) If the State determines, based on site-specific considerations, that a system has no means for having 

a sample transported and analyzed for HPC by a certified laboratory under the requisite time and 

temperature conditions specified by paragraph (a)(1) of this section and that the system is providing 

adequate disinfection in the distribution system, the requirements of paragraph (b)(6)(i) of this section do 

not apply to that system. 

(c) Monitoring requirements for systems using filtration treatment. A public water system that uses a 

surface water source or a ground water source under the influence of surface water and provides 

filtration treatment must monitor in accordance with this paragraph (c) beginning June 29, 1993, or when 

filtration is installed, whichever is later. 

(1) Turbidity measurements as required by §141.73 must be performed on representative samples of the 

system's filtered water every four hours (or more frequently) that the system serves water to the public. 

A public water system may substitute continuous turbidity monitoring for grab sample monitoring if it 

validates the continuous measurement for accuracy on a regular basis using a protocol approved by the 

State. For any systems using slow sand filtration or filtration treatment other than conventional 

treatment, direct filtration, or diatomaceous earth filtration, the State may reduce the sampling frequency 

to once per day if it determines that less frequent monitoring is sufficient to indicate effective filtration 

performance. For systems serving 500 or fewer persons, the State may reduce the turbidity sampling 

frequency to once per day, regardless of the type of filtration treatment used, if the State determines that 

less frequent monitoring is sufficient to indicate effective filtration performance. 

System size by population Samples/day1

<500 1

501 to 1,000 2

1,001 to 2,500 3

2,501 to 3,300 4

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(2) The residual disinfectant concentration of the water entering the distribution system must be 

monitored continuously, and the lowest value must be recorded each day, except that if there is a failure 

in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of 

continuous monitoring, but for no more than 5 working days following the failure of the equipment, and 

systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous 

monitoring on an ongoing basis at the frequencies each day prescribed below: 

1The day's samples cannot be taken at the same time. The sampling intervals are subject to State 

review and approval. 

If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling 

in lieu of continuous monitoring, the system must take a grab sample every 4 hours until the residual 

disinfectant concentration is equal to or greater than 0.2 mg/l. 

(3)(i) The residual disinfectant concentration must be measured at least at the same points in the 

distribution system and at the same time as total coliforms are sampled, as specified in §141.21, except 

that the State may allow a public water system which uses both a surface water source or a ground 

water source under direct influence of surface water, and a ground water source to take disinfectant 

residual samples at points other than the total coliform sampling points if the State determines that such 

points are more representative of treated (disinfected) water quality within the distribution system. 

Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in paragraph (a)(1) of 

this section, may be measured in lieu of residual disinfectant concentration. 

(ii) If the State determines, based on site-specific considerations, that a system has no means for having 

a sample transported and analyzed for HPC by a certified laboratory under the requisite time and 

temperature conditions specified by paragraph (a)(1) of this section and that the system is providing 

adequate disinfection in the distribution system, the requirements of paragraph (c)(3)(i) of this section do 

not apply to that system. 

[54 FR 27527, June 29, 1989, as amended at 59 FR 62470, Dec. 5, 1994; 60 FR 34086, June 29, 1995; 

64 FR 67465, Dec. 1, 1999; 67 FR 65252, Oct. 23, 2002; 67 FR 65901, Oct. 29, 2002; 69 FR 38856, 

June 29, 2004; 72 FR 11247, Mar. 12, 2007; 74 FR 30958, June 29, 2009] 

§ 141.75 Reporting and recordkeeping requirements. 

 top

(a) A public water system that uses a surface water source and does not provide filtration treatment 

must report monthly to the State the information specified in this paragraph (a) beginning December 31, 

1990, unless the State has determined that filtration is required in writing pursuant to section 1412(b)(7)

(C)(iii), in which case the State may specify alternative reporting requirements, as appropriate, until 

filtration is in place. A public water system that uses a ground water source under the direct influence of 

surface water and does not provide filtration treatment must report monthly to the State the information 

specified in this paragraph (a) beginning December 31, 1990, or 6 months after the State determines 

that the ground water source is under the direct influence of surface water, whichever is later, unless the 

State has determined that filtration is required in writing pursuant to §1412(b)(7)(C)(iii), in which case the 

State may specify alternative reporting requirements, as appropriate, until filtration is in place. 

(1) Source water quality information must be reported to the State within 10 days after the end of each 

month the system serves water to the public. Information that must be reported includes: 

(i) The cumulative number of months for which results are reported. 

(ii) The number of fecal and/or total coliform samples, whichever are analyzed during the month (if a 

system monitors for both, only fecal coliforms must be reported), the dates of sample collection, and the 

dates when the turbidity level exceeded 1 NTU. 

(iii) The number of samples during the month that had equal to or less than 20/100 ml fecal coliforms 

and/or equal to or less than 100/100 ml total coliforms, whichever are analyzed. 

(iv) The cumulative number of fecal or total coliform samples, whichever are analyzed, during the 

previous six months the system served water to the public. 

(v) The cumulative number of samples that had equal to or less than 20/100 ml fecal coliforms or equal 

to or less than 100/100 ml total coliforms, whichever are analyzed, during the previous six months the 

system served water to the public. 

(vi) The percentage of samples that had equal to or less than 20/100 ml fecal coliforms or equal to or 

less than 100/100 ml total coliforms, whichever are analyzed, during the previous six months the system 

served water to the public. 

(vii) The maximum turbidity level measured during the month, the date(s) of occurrence for any 

measurement(s) which exceeded 5 NTU, and the date(s) the occurrence(s) was reported to the State. 

(viii) For the first 12 months of recordkeeping, the dates and cumulative number of events during which 

the turbidity exceeded 5 NTU, and after one year of recordkeeping for turbidity measurements, the dates 

and cumulative number of events during which the turbidity exceeded 5 NTU in the previous 12 months 

the system served water to the public. 

(ix) For the first 120 months of recordkeeping, the dates and cumulative number of events during which 

the turbidity exceeded 5 NTU, and after 10 years of recordkeeping for turbidity measurements, the dates 

and cumulative number of events during which the turbidity exceeded 5 NTU in the previous 120 months 

the system served water to the public. 

System size by population Samples/day1

±500 1

501 to 1,000 2

1,001 to 2,500 3

2,501 to 3,300 4

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(2) Disinfection information specified in §141.74(b) must be reported to the State within 10 days after the 

end of each month the system serves water to the public. Information that must be reported includes: 

(i) For each day, the lowest measurement of residual disinfectant concentration in mg/l in water entering 

the distribution system. 

(ii) The date and duration of each period when the residual disinfectant concentration in water entering 

the distribution system fell below 0.2 mg/l and when the State was notified of the occurrence. 

(iii) The daily residual disinfectant concentration(s) (in mg/l) and disinfectant contact time(s) (in minutes) 

used for calculating the CT value(s). 

(iv) If chlorine is used, the daily measurement(s) of pH of disinfected water following each point of 

chlorine disinfection. 

(v) The daily measurement(s) of water temperature in °C following each point of disinfection. 

(vi) The daily CTcalc and CTcalc/CT99.9values for each disinfectant measurement or sequence and the 

sum of all CTcalc/CT99.9values ((CTcalc/CT99.9)) before or at the first customer. 

(vii) The daily determination of whether disinfection achieves adequate Giardia cyst and virus 

inactivation, i.e. , whether (CTcalc/CT99.9) is at least 1.0 or, where disinfectants other than chlorine are 

used, other indicator conditions that the State determines are appropriate, are met. 

(viii) The following information on the samples taken in the distribution system in conjunction with total 

coliform monitoring pursuant to §141.72: 

(A) Number of instances where the residual disinfectant concentration is measured; 

(B) Number of instances where the residual disinfectant concentration is not measured but heterotrophic 

bacteria plate count (HPC) is measured; 

(C) Number of instances where the residual disinfectant concentration is measured but not detected and 

no HPC is measured; 

(D) Number of instances where the residual disinfectant concentration is detected and where HPC is 

>500/ml; 

(E) Number of instances where the residual disinfectant concentration is not measured and HPC is 

>500/ml; 

(F) For the current and previous month the system served water to the public, the value of “V” in the 

following formula: 

where: 

a=the value in paragraph (a)(2)(viii)(A) of this section, 

b=the value in paragraph (a)(2)(viii)(B) of this section, 

c=the value in paragraph (a)(2)(viii)(C) of this section, 

d=the value in paragraph (a)(2)(viii)(D) of this section, and 

e=the value in paragraph (a)(2)(viii)(E) of this section. 

(G) If the State determines, based on site-specific considerations, that a system has no means for 

having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and 

temperature conditions specified by §141.74(a)(1) and that the system is providing adequate disinfection 

in the distribution system, the requirements of paragraph (a)(2)(viii) (A)–(F) of this section do not apply to 

that system. 

(ix) A system need not report the data listed in paragraphs (a)(2) (i), and (iii)–(vi) of this section if all data 

listed in paragraphs (a)(2) (i)–(viii) of this section remain on file at the system, and the State determines 

that: 

(A) The system has submitted to the State all the information required by paragraphs (a)(2) (i)–(viii) of 

this section for at least 12 months; and 

(B) The State has determined that the system is not required to provide filtration treatment. 

(3) No later than ten days after the end of each Federal fiscal year (September 30), each system must 

provide to the State a report which summarizes its compliance with all watershed control program 

requirements specified in §141.71(b)(2). 

(4) No later than ten days after the end of each Federal fiscal year (September 30), each system must 

provide to the State a report on the on-site inspection conducted during that year pursuant to §141.71(b)

(3), unless the on-site inspection was conducted by the State. If the inspection was conducted by the 

State, the State must provide a copy of its report to the public water system. 

(5)(i) Each system, upon discovering that a waterborne disease outbreak potentially attributable to that 

water system has occurred, must report that occurrence to the State as soon as possible, but no later 

than by the end of the next business day. 

(ii) If at any time the turbidity exceeds 5 NTU, the system must consult with the primacy agency as soon 

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as practical, but no later than 24 hours after the exceedance is known, in accordance with the public 

notification requirements under §141.203(b)(3). 

(iii) If at any time the residual falls below 0.2 mg/l in the water entering the distribution system, the 

system must notify the State as soon as possible, but no later than by the end of the next business day. 

The system also must notify the State by the end of the next business day whether or not the residual 

was restored to at least 0.2 mg/l within 4 hours. 

(b) A public water system that uses a surface water source or a ground water source under the direct 

influence of surface water and provides filtration treatment must report monthly to the State the 

information specified in this paragraph (b) beginning June 29, 1993, or when filtration is installed, 

whichever is later. 

(1) Turbidity measurements as required by §141.74(c)(1) must be reported within 10 days after the end 

of each month the system serves water to the public. Information that must be reported includes: 

(i) The total number of filtered water turbidity measurements taken during the month. 

(ii) The number and percentage of filtered water turbidity measurements taken during the month which 

are less than or equal to the turbidity limits specified in §141.73 for the filtration technology being used. 

(iii) The date and value of any turbidity measurements taken during the month which exceed 5 NTU. 

(2) Disinfection information specified in §141.74(c) must be reported to the State within 10 days after the 

end of each month the system serves water to the public. Information that must be reported includes: 

(i) For each day, the lowest measurement of residual disinfectant concentration in mg/l in water entering 

the distribution system. 

(ii) The date and duration of each period when the residual disinfectant concentration in water entering 

the distribution system fell below 0.2 mg/l and when the State was notified of the occurrence. 

(iii) The following information on the samples taken in the distribution system in conjunction with total 

coliform monitoring pursuant to §141.72: 

(A) Number of instances where the residual disinfectant concentration is measured; 

(B) Number of instances where the residual disinfectant concentration is not measured but heterotrophic 

bacteria plate count (HPC) is measured; 

(C) Number of instances where the residual disinfectant concentration is measured but not detected and 

no HPC is measured; 

(D) Number of instances where no residual disinfectant concentration is detected and where HPC is 

>500/ml; 

(E) Number of instances where the residual disinfectant concentration is not measured and HPC is 

>500/ml; 

(F) For the current and previous month the system serves water to the public, the value of “V” in the 

following formula: 

where: 

a=the value in paragraph (b)(2)(iii)(A) of this section, 

b=the value in paragraph (b)(2)(iii)(B) of this section, 

c=the value in paragraph (b)(2)(iii)(C) of this section, 

d=the value in paragraph (b)(2)(iii)(D) of this section, and 

e=the value in paragraph (b)(2)(iii)(E) of this section. 

(G) If the State determines, based on site-specific considerations, that a system has no means for 

having a sample transported and analyzed for HPC by a certified laboratory within the requisite time and 

temperature conditions specified by §141.74(a)(1) and that the system is providing adequate disinfection 

in the distribution system, the requirements of paragraph (b)(2)(iii) (A)–(F) of this section do not apply. 

(iv) A system need not report the data listed in paragraph (b)(2)(i) of this section if all data listed in 

paragraphs (b)(2) (i)–(iii) of this section remain on file at the system and the State determines that the 

system has submitted all the information required by paragraphs (b)(2) (i)–(iii) of this section for at least 

12 months. 

(3)(i) Each system, upon discovering that a waterborne disease outbreak potentially attributable to that 

water system has occurred, must report that occurrence to the State as soon as possible, but no later 

than by the end of the next business day. 

(ii) If at any time the turbidity exceeds 5 NTU, the system must consult with the primacy agency as soon 

as practical, but no later than 24 hours after the exceedance is known, in accordance with the public 

notification requirements under §141.203(b)(3). 

(iii) If at any time the residual falls below 0.2 mg/l in the water entering the distribution system, the 

system must notify the State as soon as possible, but no later than by the end of the next business day. 

The system also must notify the State by the end of the next business day whether or not the residual 

was restored to at least 0.2 mg/l within 4 hours. 

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[54 FR 27527, June 29, 1989, as amended at 65 FR 26022, May 4, 2000; 69 FR 38856, June 29, 2004] 

§ 141.76 Recycle provisions. 

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(a) Applicability. All subpart H systems that employ conventional filtration or direct filtration treatment and 

that recycle spent filter backwash water, thickener supernatant, or liquids from dewatering processes 

must meet the requirements in paragraphs (b) through (d) of this section. 

(b) Reporting. A system must notify the State in writing by Decemeber 8, 2003, if the system recycles 

spent filter backwash water, thickener supernatant, or liquids from dewatering processes. This 

notification must include, at a minimum, the information specified in paragraphs (b)(1) and (2) of this 

section. 

(1) A plant schematic showing the origin of all flows which are recycled (including, but not limited to, 

spent filter backwash water, thickener supernatant, and liquids from dewatering processes), the 

hydraulic conveyance used to transport them, and the location where they are re-introduced back into 

the treatment plant. 

(2) Typical recycle flow in gallons per minute (gpm), the highest observed plant flow experienced in the 

previous year (gpm), design flow for the treatment plant (gpm), and State-approved operating capacity 

for the plant where the State has made such determinations. 

(c) Treatment technique requirement. Any system that recycles spent filter backwash water, thickener 

supernatant, or liquids from dewatering processes must return these flows through the processes of a 

system's existing conventional or direct filtration system as defined in §141.2 or at an alternate location 

approved by the State by June 8, 2004. If capital improvements are required to modify the recycle 

location to meet this requirement, all capital improvements must be completed no later than June 8, 

2006. 

(d) Recordkeeping. The system must collect and retain on file recycle flow information specified in 

paragraphs (d)(1) through (6) of this section for review and evaluation by the State beginning June 8, 

2004. 

(1) Copy of the recycle notification and information submitted to the State under paragraph (b) of this 

section. 

(2) List of all recycle flows and the frequency with which they are returned. 

(3) Average and maximum backwash flow rate through the filters and the average and maximum 

duration of the filter backwash process in minutes. 

(4) Typical filter run length and a written summary of how filter run length is determined. 

(5) The type of treatment provided for the recycle flow. 

(6) Data on the physical dimensions of the equalization and/or treatment units, typical and maximum 

hydraulic loading rates, type of treatment chemicals used and average dose and frequency of use, and 

frequency at which solids are removed, if applicable. 

[66 FR 31103, June 8, 2001] 

Subpart I—Control of Lead and Copper 

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Source: 56 FR 26548, June 7, 1991, unless otherwise noted. 

§ 141.80 General requirements. 

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(a) Applicability and effective dates. (1) The requirements of this subpart I constitute the national primary 

drinking water regulations for lead and copper. Unless otherwise indicated, each of the provisions of this 

subpart applies to community water systems and non-transient, non-community water systems 

(hereinafter referred to as “water systems” or “systems”). 

(2) [Reserved] 

(b) Scope. These regulations establish a treatment technique that includes requirements for corrosion 

control treatment, source water treatment, lead service line replacement, and public education. These 

requirements are triggered, in some cases, by lead and copper action levels measured in samples 

collected at consumers' taps. 

(c) Lead and copper action levels. (1) The lead action level is exceeded if the concentration of lead in 

more than 10 percent of tap water samples collected during any monitoring period conducted in 

accordance with §141.86 is greater than 0.015 mg/L ( i.e. , if the “90th percentile” lead level is greater 

than 0.015 mg/L). 

(2) The copper action level is exceeded if the concentration of copper in more than 10 percent of tap 

water samples collected during any monitoring period conducted in accordance with §141.86 is greater 

than 1.3 mg/L ( i.e. , if the “90th percentile” copper level is greater than 1.3 mg/L). 

(3) The 90th percentile lead and copper levels shall be computed as follows: 

(i) The results of all lead or copper samples taken during a monitoring period shall be placed in 

ascending order from the sample with the lowest concentration to the sample with the highest 

concentration. Each sampling result shall be assigned a number, ascending by single integers beginning 

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with the number 1 for the sample with the lowest contaminant level. The number assigned to the sample 

with the highest contaminant level shall be equal to the total number of samples taken. 

(ii) The number of samples taken during the monitoring period shall be multiplied by 0.9. 

(iii) The contaminant concentration in the numbered sample yielded by the calculation in paragraph (c)

(3)(ii) is the 90th percentile contaminant level. 

(iv) For water systems serving fewer than 100 people that collect 5 samples per monitoring period, the 

90th percentile is computed by taking the average of the highest and second highest concentrations. 

(v) For a public water system that has been allowed by the State to collect fewer than five samples in 

accordance with §141.86(c), the sample result with the highest concentration is considered the 90th 

percentile value. 

(d) Corrosion control treatment requirements. (1) All water systems shall install and operate optimal 

corrosion control treatment as defined in §141.2. 

(2) Any water system that complies with the applicable corrosion control treatment requirements 

specified by the State under §§141.81 and 141.82 shall be deemed in compliance with the treatment 

requirement contained in paragraph (d)(1) of this section. 

(e) Source water treatment requirements. Any system exceeding the lead or copper action level shall 

implement all applicable source water treatment requirements specified by the State under §141.83. 

(f) Lead service line replacement requirements. Any system exceeding the lead action level after 

implementation of applicable corrosion control and source water treatment requirements shall complete 

the lead service line replacement requirements contained in §141.84. 

(g) Public education requirements. Pursuant to §141.85, all water systems must provide a consumer 

notice of lead tap water monitoring results to persons served at the sites (taps) that are tested. Any 

system exceeding the lead action level shall implement the public education requirements. 

(h) Monitoring and analytical requirements. Tap water monitoring for lead and copper, monitoring for 

water quality parameters, source water monitoring for lead and copper, and analyses of the monitoring 

results under this subpart shall be completed in compliance with §§141.86, 141.87, 141.88, and 141.89. 

(i) Reporting requirements. Systems shall report to the State any information required by the treatment 

provisions of this subpart and §141.90. 

(j) Recordkeeping requirements. Systems shall maintain records in accordance with §141.91. 

(k) Violation of national primary drinking water regulations. Failure to comply with the applicable 

requirements of §§141.80–141.91, including requirements established by the State pursuant to these 

provisions, shall constitute a violation of the national primary drinking water regulations for lead and/or 

copper. 

[56 FR 26548, June 7, 1991; 57 FR 28788, June 29, 1992, as amended at 72 FR 57814, Oct. 10, 2007] 

§ 141.81 Applicability of corrosion control treatment steps to small, medium-size and 

large water systems. 

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(a) Systems shall complete the applicable corrosion control treatment requirements described in 

§141.82 by the deadlines established in this section. 

(1) A large system (serving >50,000 persons) shall complete the corrosion control treatment steps 

specified in paragraph (d) of this section, unless it is deemed to have optimized corrosion control under 

paragraph (b)(2) or (b)(3) of this section. 

(2) A small system (serving ≤3300 persons) and a medium-size system (serving >3,300 and ≤50,000 

persons) shall complete the corrosion control treatment steps specified in paragraph (e) of this section, 

unless it is deemed to have optimized corrosion control under paragraph (b)(1), (b)(2), or (b)(3) of this 

section. 

(b) A system is deemed to have optimized corrosion control and is not required to complete the 

applicable corrosion control treatment steps identified in this section if the system satisfies one of the 

criteria specified in paragraphs (b)(1) through (b)(3) of this section. Any such system deemed to have 

optimized corrosion control under this paragraph, and which has treatment in place, shall continue to 

operate and maintain optimal corrosion control treatment and meet any requirements that the State 

determines appropriate to ensure optimal corrosion control treatment is maintained. 

(1) A small or medium-size water system is deemed to have optimized corrosion control if the system 

meets the lead and copper action levels during each of two consecutive six-month monitoring periods 

conducted in accordance with §141.86. 

(2) Any water system may be deemed by the State to have optimized corrosion control treatment if the 

system demonstrates to the satisfaction of the State that it has conducted activities equivalent to the 

corrosion control steps applicable to such system under this section. If the State makes this 

determination, it shall provide the system with written notice explaining the basis for its decision and 

shall specify the water quality control parameters representing optimal corrosion control in accordance 

with §141.82(f). Water systems deemed to have optimized corrosion control under this paragraph shall 

operate in compliance with the State-designated optimal water quality control parameters in accordance 

with §141.82(g) and continue to conduct lead and copper tap and water quality parameter sampling in 

accordance with §141.86(d)(3) and §141.87(d), respectively. A system shall provide the State with the 

following information in order to support a determination under this paragraph: 

(i) The results of all test samples collected for each of the water quality parameters in §141.82(c)(3). 

(ii) A report explaining the test methods used by the water system to evaluate the corrosion control 

treatments listed in §141.82(c)(1), the results of all tests conducted, and the basis for the system's 

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selection of optimal corrosion control treatment; 

(iii) A report explaining how corrosion control has been installed and how it is being maintained to insure 

minimal lead and copper concentrations at consumers' taps; and 

(iv) The results of tap water samples collected in accordance with §141.86 at least once every six 

months for one year after corrosion control has been installed. 

(3) Any water system is deemed to have optimized corrosion control if it submits results of tap water 

monitoring conducted in accordance with §141.86 and source water monitoring conducted in 

accordance with §141.88 that demonstrates for two consecutive 6-month monitoring periods that the 

difference between the 90th percentile tap water lead level computed under §141.80(c)(3), and the 

highest source water lead concentration is less than the Practical Quantitation Level for lead specified in 

§141.89(a)(1)(ii). 

(i) Those systems whose highest source water lead level is below the Method Detection Limit may also 

be deemed to have optimized corrosion control under this paragraph if the 90th percentile tap water lead 

level is less than or equal to the Practical Quantitation Level for lead for two consecutive 6-month 

monitoring periods. 

(ii) Any water system deemed to have optimized corrosion control in accordance with this paragraph 

shall continue monitoring for lead and copper at the tap no less frequently than once every three 

calendar years using the reduced number of sites specified in §141.86(c) and collecting the samples at 

times and locations specified in §141.86(d)(4)(iv). Any such system that has not conducted a round of 

monitoring pursuant to §141.86(d) since September 30, 1997, shall complete a round of monitoring 

pursuant to this paragraph no later than September 30, 2000. 

(iii) Any water system deemed to have optimized corrosion control pursuant to this paragraph shall notify 

the State in writing pursuant to §141.90(a)(3) of any upcoming long-term change in treatment or addition 

of a new source as described in that section. The State must review and approve the addition of a new 

source or long-term change in water treatment before it is implemented by the water system. The State 

may require any such system to conduct additional monitoring or to take other action the State deems 

appropriate to ensure that such systems maintain minimal levels of corrosion in the distribution system. 

(iv) As of July 12, 2001, a system is not deemed to have optimized corrosion control under this 

paragraph, and shall implement corrosion control treatment pursuant to paragraph (b)(3)(v) of this 

section unless it meets the copper action level. 

(v) Any system triggered into corrosion control because it is no longer deemed to have optimized 

corrosion control under this paragraph shall implement corrosion control treatment in accordance with 

the deadlines in paragraph (e) of this section. Any such large system shall adhere to the schedule 

specified in that paragraph for medium-size systems, with the time periods for completing each step 

being triggered by the date the system is no longer deemed to have optimized corrosion control under 

this paragraph. 

(c) Any small or medium-size water system that is required to complete the corrosion control steps due 

to its exceedance of the lead or copper action level may cease completing the treatment steps whenever 

the system meets both action levels during each of two consecutive monitoring periods conducted 

pursuant to §141.86 and submits the results to the State. If any such water system thereafter exceeds 

the lead or copper action level during any monitoring period, the system (or the State, as the case may 

be) shall recommence completion of the applicable treatment steps, beginning with the first treatment 

step which was not previously completed in its entirety. The State may require a system to repeat 

treatment steps previously completed by the system where the State determines that this is necessary to 

implement properly the treatment requirements of this section. The State shall notify the system in 

writing of such a determination and explain the basis for its decision. The requirement for any small- or 

medium-size system to implement corrosion control treatment steps in accordance with paragraph (e) of 

this section (including systems deemed to have optimized corrosion control under paragraph (b)(1) of 

this section) is triggered whenever any small- or medium-size system exceeds the lead or copper action 

level. 

(d) Treatment steps and deadlines for large systems. Except as provided in paragraph (b) (2) and (3) of 

this section, large systems shall complete the following corrosion control treatment steps (described in 

the referenced portions of §§141.82, 141.86, and 141.87) by the indicated dates. 

(1) Step 1: The system shall conduct initial monitoring (§141.86(d)(1) and §141.87(b)) during two 

consecutive six-month monitoring periods by January 1, 1993. 

(2) Step 2: The system shall complete corrosion control studies (§141.82(c)) by July 1, 1994. 

(3) Step 3: The State shall designate optimal corrosion control treatment (§141.82(d)) by January 1, 

1995. 

(4) Step 4: The system shall install optimal corrosion control treatment (§141.82(e)) by January 1, 1997. 

(5) Step 5: The system shall complete follow-up sampling (§141.86(d)(2) and §141.87(c)) by January 1, 

1998. 

(6) Step 6: The State shall review installation of treatment and designate optimal water quality control 

parameters (§141.82(f)) by July 1, 1998. 

(7) Step 7: The system shall operate in compliance with the State-specified optimal water quality control 

parameters (§141.82(g)) and continue to conduct tap sampling (§141.86(d)(3) and §141.87(d)). 

(e) Treatment Steps and deadlines for small and medium-size systems. Except as provided in paragraph 

(b) of this section, small and medium-size systems shall complete the following corrosion control 

treatment steps (described in the referenced portions of §§141.82, 141.86 and 141.87) by the indicated 

time periods. 

(1) Step 1: The system shall conduct initial tap sampling (§141.86(d)(1) and §141.87(b)) until the system 

either exceeds the lead or copper action level or becomes eligible for reduced monitoring under §141.86

(d)(4). A system exceeding the lead or copper action level shall recommend optimal corrosion control 

treatment (§141.82(a)) within six months after the end of the monitoring period during which it exceeds 

one of the action levels. 

(2) Step 2: Within 12 months after the end of the monitoring period during which a system exceeds the 

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lead or copper action level, the State may require the system to perform corrosion control studies 

(§141.82(b)). If the State does not require the system to perform such studies, the State shall specify 

optimal corrosion control treatment (§141.82(d)) within the following timeframes: 

(i) For medium-size systems, within 18 months after the end of the monitoring period during which such 

system exceeds the lead or copper action level. 

(ii) For small systems, within 24 months after the end of the monitoring period during which such system 

exceeds the lead or copper action level. 

(3) Step 3: If the State requires a system to perform corrosion control studies under step 2, the system 

shall complete the studies (§141.82(c)) within 18 months after the State requires that such studies be 

conducted. 

(4) Step 4: If the system has performed corrosion control studies under step 2, the State shall designate 

optimal corrosion control treatment (§141.82(d)) within 6 months after completion of step 3. 

(5) Step 5: The system shall install optimal corrosion control treatment (§141.82(e)) within 24 months 

after the State designates such treatment. 

(6) Step 6: The system shall complete follow-up sampling (§141.86(d)(2) and §141.87(c)) within 36 

months after the State designates optimal corrosion control treatment. 

(7) Step 7: The State shall review the system's installation of treatment and designate optimal water 

quality control parameters (§141.82(f)) within 6 months after completion of step 6. 

(8) Step 8: The system shall operate in compliance with the State-designated optimal water quality 

control parameters (§141.82(g)) and continue to conduct tap sampling (§141.86(d)(3) and §141.87(d)). 

[56 FR 26548, June 7, 1991, as amended at 59 FR 33862, June 30, 1994; 65 FR 2004, Jan. 12, 2000; 

72 FR 57814, Oct. 10, 2007] 

§ 141.82 Description of corrosion control treatment requirements. 

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Each system shall complete the corrosion control treatment requirements described below which are 

applicable to such system under §141.81. 

(a) System recommendation regarding corrosion control treatment. Based upon the results of lead and 

copper tap monitoring and water quality parameter monitoring, small and medium-size water systems 

exceeding the lead or copper action level shall recommend installation of one or more of the corrosion 

control treatments listed in paragraph (c)(1) of this section which the system believes constitutes optimal 

corrosion control for that system. The State may require the system to conduct additional water quality 

parameter monitoring in accordance with §141.87(b) to assist the State in reviewing the system's 

recommendation. 

(b) State decision to require studies of corrosion control treatment (applicable to small and medium-size 

systems). The State may require any small or medium-size system that exceeds the lead or copper 

action level to perform corrosion control studies under paragraph (c) of this section to identify optimal 

corrosion control treatment for the system. 

(c) Performance of corrosion control studies. (1) Any public water system performing corrosion control 

studies shall evaluate the effectiveness of each of the following treatments, and, if appropriate, 

combinations of the following treatments to identify the optimal corrosion control treatment for that 

system: 

(i) Alkalinity and pH adjustment; 

(ii) Calcium hardness adjustment; and 

(iii) The addition of a phosphate or silicate based corrosion inhibitor at a concentration sufficient to 

maintain an effective residual concentration in all test tap samples. 

(2) The water system shall evaluate each of the corrosion control treatments using either pipe rig/loop 

tests, metal coupon tests, partial-system tests, or analyses based on documented analogous treatments 

with other systems of similar size, water chemistry and distribution system configuration. 

(3) The water system shall measure the following water quality parameters in any tests conducted under 

this paragraph before and after evaluating the corrosion control treatments listed above: 

(i) Lead; 

(ii) Copper; 

(iii) pH; 

(iv) Alkalinity; 

(v) Calcium; 

(vi) Conductivity; 

(vii) Orthophosphate (when an inhibitor containing a phosphate compound is used); 

(viii) Silicate (when an inhibitor containing a silicate compound is used); 

(ix) Water temperature. 

(4) The water system shall identify all chemical or physical constraints that limit or prohibit the use of a 

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particular corrosion control treatment and document such constraints with at least one of the following: 

(i) Data and documentation showing that a particular corrosion control treatment has adversely affected 

other water treatment processes when used by another water system with comparable water quality 

characteristics; and/or 

(ii) Data and documentation demonstrating that the water system has previously attempted to evaluate a 

particular corrosion control treatment and has found that the treatment is ineffective or adversely affects 

other water quality treatment processes. 

(5) The water system shall evaluate the effect of the chemicals used for corrosion control treatment on 

other water quality treatment processes. 

(6) On the basis of an analysis of the data generated during each evaluation, the water system shall 

recommend to the State in writing the treatment option that the corrosion control studies indicate 

constitutes optimal corrosion control treatment for that system. The water system shall provide a 

rationale for its recommendation along with all supporting documentation specified in paragraphs (c) (1) 

through (5) of this section. 

(d) State designation of optimal corrosion control treatment. (1) Based upon consideration of available 

information including, where applicable, studies performed under paragraph (c) of this section and a 

system's recommended treatment alternative, the State shall either approve the corrosion control 

treatment option recommended by the system, or designate alternative corrosion control treatment(s) 

from among those listed in paragraph (c)(1) of this section. When designating optimal treatment the 

State shall consider the effects that additional corrosion control treatment will have on water quality 

parameters and on other water quality treatment processes. 

(2) The State shall notify the system of its decision on optimal corrosion control treatment in writing and 

explain the basis for this determination. If the State requests additional information to aid its review, the 

water system shall provide the information. 

(e) Installation of optimal corrosion control. Each system shall properly install and operate throughout its 

distribution system the optimal corrosion control treatment designated by the State under paragraph (d) 

of this section. 

(f) State review of treatment and specification of optimal water quality control parameters. The State 

shall evaluate the results of all lead and copper tap samples and water quality parameter samples 

submitted by the water system and determine whether the system has properly installed and operated 

the optimal corrosion control treatment designated by the State in paragraph (d) of this section. Upon 

reviewing the results of tap water and water quality parameter monitoring by the system, both before and 

after the system installs optimal corrosion control treatment, the State shall designate: 

(1) A minimum value or a range of values for pH measured at each entry point to the distribution system; 

(2) A minimum pH value, measured in all tap samples. Such value shall be equal to or greater than 7.0, 

unless the State determines that meeting a pH level of 7.0 is not technologically feasible or is not 

necessary for the system to optimize corrosion control; 

(3) If a corrosion inhibitor is used, a minimum concentration or a range of concentrations for the inhibitor, 

measured at each entry point to the distribution system and in all tap samples, that the State determines 

is necessary to form a passivating film on the interior walls of the pipes of the distribution system; 

(4) If alkalinity is adjusted as part of optimal corrosion control treatment, a minimum concentration or a 

range of concentrations for alkalinity, measured at each entry point to the distribution system and in all 

tap samples; 

(5) If calcium carbonate stabilization is used as part of corrosion control, a minimum concentration or a 

range of concentrations for calcium, measured in all tap samples. 

The values for the applicable water quality control parameters listed above shall be those that the State 

determines to reflect optimal corrosion control treatment for the system. The State may designate values 

for additional water quality control parameters determined by the State to reflect optimal corrosion 

control for the system. The State shall notify the system in writing of these determinations and explain 

the basis for its decisions. 

(g) Continued operation and monitoring. All systems optimizing corrosion control shall continue to 

operate and maintain optimal corrosion control treatment, including maintaining water quality parameters 

at or above minimum values or within ranges designated by the State under paragraph (f) of this section, 

in accordance with this paragraph for all samples collected under §141.87(d) through (f). Compliance 

with the requirements of this paragraph shall be determined every six months, as specified under 

§141.87(d). A water system is out of compliance with the requirements of this paragraph for a six-month 

period if it has excursions for any State-specified parameter on more than nine days during the period. 

An excursion occurs whenever the daily value for one or more of the water quality parameters measured 

at a sampling location is below the minimum value or outside the range designated by the State. Daily 

values are calculated as follows. States have discretion to delete results of obvious sampling errors from 

this calculation. 

(1) On days when more than one measurement for the water quality parameter is collected at the 

sampling location, the daily value shall be the average of all results collected during the day regardless 

of whether they are collected through continuous monitoring, grab sampling, or a combination of both. If 

EPA has approved an alternative formula under §142.16 of this chapter in the State's application for a 

program revision submitted pursuant to §142.12 of this chapter, the State's formula shall be used to 

aggregate multiple measurements taken at a sampling point for the water quality parameter in lieu of the 

formula in this paragraph. 

(2) On days when only one measurement for the water quality parameter is collected at the sampling 

location, the daily value shall be the result of that measurement. 

(3) On days when no measurement is collected for the water quality parameter at the sampling location, 

the daily value shall be the daily value calculated on the most recent day on which the water quality 

parameter was measured at the sample site. 

(h) Modification of State treatment decisions. Upon its own initiative or in response to a request by a 

water system or other interested party, a State may modify its determination of the optimal corrosion 

control treatment under paragraph (d) of this section or optimal water quality control parameters under 

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paragraph (f) of this section. A request for modification by a system or other interested party shall be in 

writing, explain why the modification is appropriate, and provide supporting documentation. The State 

may modify its determination where it concludes that such change is necessary to ensure that the 

system continues to optimize corrosion control treatment. A revised determination shall be made in 

writing, set forth the new treatment requirements, explain the basis for the State's decision, and provide 

an implementation schedule for completing the treatment modifications. 

(i) Treatment decisions by EPA in lieu of the State. Pursuant to the procedures in §142.19, the EPA 

Regional Administrator may review treatment determinations made by a State under paragraphs (d), (f), 

or (h) of this section and issue federal treatment determinations consistent with the requirements of 

those paragraphs where the Regional Administrator finds that: 

(1) A State has failed to issue a treatment determination by the applicable deadlines contained in 

§141.81, 

(2) A State has abused its discretion in a substantial number of cases or in cases affecting a substantial 

population, or 

(3) The technical aspects of a State's determination would be indefensible in an expected Federal 

enforcement action taken against a system. 

[56 FR 26548, June 7, 1991, as amended at 65 FR 2004, Jan. 12, 2000] 

§ 141.83 Source water treatment requirements. 

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Systems shall complete the applicable source water monitoring and treatment requirements (described 

in the referenced portions of paragraph (b) of this section, and in §§141.86, and 141.88) by the following 

deadlines. 

(a) Deadlines for completing source water treatment steps— (1) Step 1: A system exceeding the lead or 

copper action level shall complete lead and copper source water monitoring (§141.88(b)) and make a 

treatment recommendation to the State (§141.83(b)(1)) no later than 180 days after the end of the 

monitoring period during which the lead or copper action level was exceeded. 

(2) Step 2: The State shall make a determination regarding source water treatment (§141.83(b)(2)) 

within 6 months after submission of monitoring results under step 1. 

(3) Step 3: If the State requires installation of source water treatment, the system shall install the 

treatment (§141.83(b)(3)) within 24 months after completion of step 2. 

(4) Step 4: The system shall complete follow-up tap water monitoring (§141.86(d)(2) and source water 

monitoring (§141.88(c)) within 36 months after completion of step 2. 

(5) Step 5: The State shall review the system's installation and operation of source water treatment and 

specify maximum permissible source water levels (§141.83(b)(4)) within 6 months after completion of 

step 4. 

(6) Step 6: The system shall operate in compliance with the State-specified maximum permissible lead 

and copper source water levels (§141.83(b)(4)) and continue source water monitoring (§141.88(d)). 

(b) Description of source water treatment requirements —(1) System treatment recommendation. Any 

system which exceeds the lead or copper action level shall recommend in writing to the State the 

installation and operation of one of the source water treatments listed in paragraph (b)(2) of this section. 

A system may recommend that no treatment be installed based upon a demonstration that source water 

treatment is not necessary to minimize lead and copper levels at users' taps. 

(2) State determination regarding source water treatment. The State shall complete an evaluation of the 

results of all source water samples submitted by the water system to determine whether source water 

treatment is necessary to minimize lead or copper levels in water delivered to users' taps. If the State 

determines that treatment is needed, the State shall either require installation and operation of the 

source water treatment recommended by the system (if any) or require the installation and operation of 

another source water treatment from among the following: Ion exchange, reverse osmosis, lime 

softening or coagulation/filtration. If the State requests additional information to aid in its review, the 

water system shall provide the information by the date specified by the State in its request. The State 

shall notify the system in writing of its determination and set forth the basis for its decision. 

(3) Installation of source water treatment. Each system shall properly install and operate the source 

water treatment designated by the State under paragraph (b)(2) of this section. 

(4) State review of source water treatment and specification of maximum permissible source water 

levels. The State shall review the source water samples taken by the water system both before and after 

the system installs source water treatment, and determine whether the system has properly installed and 

operated the source water treatment designated by the State. Based upon its review, the State shall 

designate the maximum permissible lead and copper concentrations for finished water entering the 

distribution system. Such levels shall reflect the contaminant removal capability of the treatment properly 

operated and maintained. The State shall notify the system in writing and explain the basis for its 

decision. 

(5) Continued operation and maintenance. Each water system shall maintain lead and copper levels 

below the maximum permissible concentrations designated by the State at each sampling point 

monitored in accordance with §141.88. The system is out of compliance with this paragraph if the level 

of lead or copper at any sampling point is greater than the maximum permissible concentration 

designated by the State. 

(6) Modification of State treatment decisions. Upon its own initiative or in response to a request by a 

water system or other interested party, a State may modify its determination of the source water 

treatment under paragraph (b)(2) of this section, or maximum permissible lead and copper 

concentrations for finished water entering the distribution system under paragraph (b)(4) of this section. 

A request for modification by a system or other interested party shall be in writing, explain why the 

modification is appropriate, and provide supporting documentation. The State may modify its 

determination where it concludes that such change is necessary to ensure that the system continues to 

minimize lead and copper concentrations in source water. A revised determination shall be made in 

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writing, set forth the new treatment requirements, explain the basis for the State's decision, and provide 

an implementation schedule for completing the treatment modifications. 

(7) Treatment decisions by EPA in lieu of the State. Pursuant to the procedures in §142.19, the EPA 

Regional Administrator may review treatment determinations made by a State under paragraphs (b) (2), 

(4), or (6) of this section and issue Federal treatment determinations consistent with the requirements of 

those paragraphs where the Administrator finds that: 

(i) A State has failed to issue a treatment determination by the applicable deadlines contained in 

§141.83(a), 

(ii) A state has abused its discretion in a substantial number of cases or in cases affecting a substantial 

population, or 

(iii) The technical aspects of a State's determination would be indefensible in an expected Federal 

enforcement action taken against a system. 

[56 FR 26548, June 7, 1991, as amended at 72 FR 57815, Oct. 10, 2007] 

§ 141.84 Lead service line replacement requirements. 

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(a) Systems that fail to meet the lead action level in tap samples taken pursuant to §141.86(d)(2), after 

installing corrosion control and/or source water treatment (whichever sampling occurs later), shall 

replace lead service lines in accordance with the requirements of this section. If a system is in violation 

of §141.81 or §141.83 for failure to install source water or corrosion control treatment, the State may 

require the system to commence lead service line replacement under this section after the date by which 

the system was required to conduct monitoring under §141.86(d)(2) has passed. 

(b)(1) A water system shall replace annually at least 7 percent of the initial number of lead service lines 

in its distribution system. The initial number of lead service lines is the number of lead lines in place at 

the time the replacement program begins. The system shall identify the initial number of lead service 

lines in its distribution system, including an identification of the portion(s) owned by the system, based 

on a materials evaluation, including the evaluation required under §141.86(a) and relevant legal 

authorities (e.g., contracts, local ordinances) regarding the portion owned by the system. The first year 

of lead service line replacement shall begin on the first day following the end of the monitoring period in 

which the action level was exceeded under paragraph (a) of this section. If monitoring is required 

annually or less frequently, the end of the monitoring period is September 30 of the calendar year in 

which the sampling occurs. If the State has established an alternate monitoring period, then the end of 

the monitoring period will be the last day of that period. 

(2) Any water system resuming a lead service line replacement program after the cessation of its lead 

service line replacement program as allowed by paragraph (f) of this section shall update its inventory of 

lead service lines to include those sites that were previously determined not to require replacement 

through the sampling provision under paragraph (c) of this section. The system will then divide the 

updated number of remaining lead service lines by the number of remaining years in the program to 

determine the number of lines that must be replaced per year (7 percent lead service line replacement is 

based on a 15-year replacement program, so, for example, systems resuming lead service line 

replacement after previously conducting two years of replacement would divide the updated inventory by 

13). For those systems that have completed a 15-year lead service line replacement program, the State 

will determine a schedule for replacing or retesting lines that were previously tested out under the 

replacement program when the system re-exceeds the action level. 

(c) A system is not required to replace an individual lead service line if the lead concentration in all 

service line samples from that line, taken pursuant to §141.86(b)(3), is less than or equal to 0.015 mg/L. 

(d) A water system shall replace that portion of the lead service line that it owns. In cases where the 

system does not own the entire lead service line, the system shall notify the owner of the line, or the 

owner's authorized agent, that the system will replace the portion of the service line that it owns and 

shall offer to replace the owner's portion of the line. A system is not required to bear the cost of replacing 

the privately-owned portion of the line, nor is it required to replace the privately-owned portion where the 

owner chooses not to pay the cost of replacing the privately-owned portion of the line, or where 

replacing the privately-owned portion would be precluded by State, local or common law. A water 

system that does not replace the entire length of the service line also shall complete the following tasks. 

(1) At least 45 days prior to commencing with the partial replacement of a lead service line, the water 

system shall provide notice to the resident(s) of all buildings served by the line explaining that they may 

experience a temporary increase of lead levels in their drinking water, along with guidance on measures 

consumers can take to minimize their exposure to lead. The State may allow the water system to 

provide notice under the previous sentence less than 45 days prior to commencing partial lead service 

line replacement where such replacement is in conjunction with emergency repairs. In addition, the 

water system shall inform the resident(s) served by the line that the system will, at the system's 

expense, collect a sample from each partially-replaced lead service line that is representative of the 

water in the service line for analysis of lead content, as prescribed under §141.86(b)(3), within 72 hours 

after the completion of the partial replacement of the service line. The system shall collect the sample 

and report the results of the analysis to the owner and the resident(s) served by the line within three 

business days of receiving the results. Mailed notices post-marked within three business days of 

receiving the results shall be considered “on time.” 

(2) The water system shall provide the information required by paragraph (d)(1) of this section to the 

residents of individual dwellings by mail or by other methods approved by the State. In instances where 

multi-family dwellings are served by the line, the water system shall have the option to post the 

information at a conspicuous location. 

(e) The State shall require a system to replace lead service lines on a shorter schedule than that 

required by this section, taking into account the number of lead service lines in the system, where such a 

shorter replacement schedule is feasible. The State shall make this determination in writing and notify 

the system of its finding within 6 months after the system is triggered into lead service line replacement 

based on monitoring referenced in paragraph (a) of this section. 

(f) Any system may cease replacing lead service lines whenever first draw samples collected pursuant to 

§141.86(b)(2) meet the lead action level during each of two consecutive monitoring periods and the 

system submits the results to the State. If first draw tap samples collected in any such system thereafter 

exceeds the lead action level, the system shall recommence replacing lead service lines pursuant to 

paragraph (b)(2) of this section. 

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(g) To demonstrate compliance with paragraphs (a) through (d) of this section, a system shall report to 

the State the information specified in §141.90(e). 

[56 FR 26548, June 7, 1991; 57 FR 28788, June 29, 1992, as amended at 65 FR 2005, Jan. 12, 2000; 

72 FR 57815, Oct. 10, 2007] 

§ 141.85 Public education and supplemental monitoring requirements. 

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All water systems must deliver a consumer notice of lead tap water monitoring results to persons served 

by the water system at sites that are tested, as specified in paragraph (d) of this section. A water system 

that exceeds the lead action level based on tap water samples collected in accordance with §141.86 

shall deliver the public education materials contained in paragraph (a) of this section in accordance with 

the requirements in paragraph (b) of this section. Water systems that exceed the lead action level must 

sample the tap water of any customer who requests it in accordance with paragraph (c) of this section. 

(a) Content of written public education materials —(1) Community water systems and non-transient noncommunity water systems. Water systems must include the following elements in printed materials (e.g., 

brochures and pamphlets) in the same order as listed below. In addition, language in paragraphs (a)(1)

(i) through (ii) and (a)(1)(vi) of this section must be included in the materials, exactly as written, except 

for the text in brackets in these paragraphs for which the water system must include system-specific 

information. Any additional information presented by a water system must be consistent with the 

information below and be in plain language that can be understood by the general public. Water systems 

must submit all written public education materials to the State prior to delivery. The State may require 

the system to obtain approval of the content of written public materials prior to delivery. 

(i) IMPORTANT INFORMATION ABOUT LEAD IN YOUR DRINKING WATER. [INSERT NAME OF 

WATER SYSTEM] found elevated levels of lead in drinking water in some homes/buildings. Lead can 

cause serious health problems, especially for pregnant women and young children. Please read this 

information closely to see what you can do to reduce lead in your drinking water. 

(ii) Health effects of lead. Lead can cause serious health problems if too much enters your body from 

drinking water or other sources. It can cause damage to the brain and kidneys, and can interfere with the 

production of red blood cells that carry oxygen to all parts of your body. The greatest risk of lead 

exposure is to infants, young children, and pregnant women. Scientists have linked the effects of lead on 

the brain with lowered IQ in children. Adults with kidney problems and high blood pressure can be 

affected by low levels of lead more than healthy adults. Lead is stored in the bones, and it can be 

released later in life. During pregnancy, the child receives lead from the mother's bones, which may 

affect brain development. 

(iii) Sources of lead. (A) Explain what lead is. 

(B) Explain possible sources of lead in drinking water and how lead enters drinking water. Include 

information on home/building plumbing materials and service lines that may contain lead. 

(C) Discuss other important sources of lead exposure in addition to drinking water (e.g., paint). 

(iv) Discuss the steps the consumer can take to reduce their exposure to lead in drinking water. 

(A) Encourage running the water to flush out the lead. 

(B) Explain concerns with using hot water from the tap and specifically caution against the use of hot 

water for preparing baby formula. 

(C) Explain that boiling water does not reduce lead levels. 

(D) Discuss other options consumers can take to reduce exposure to lead in drinking water, such as 

alternative sources or treatment of water. 

(E) Suggest that parents have their child's blood tested for lead. 

(v) Explain why there are elevated levels of lead in the system's drinking water (if known) and what the 

water system is doing to reduce the lead levels in homes/buildings in this area. 

(vi) For more information, call us at [INSERT YOUR NUMBER] [(IF APPLICABLE), or visit our Web site 

at [INSERT YOUR WEB SITE HERE]]. For more information on reducing lead exposure around your 

home/building and the health effects of lead, visit EPA's Web site at http://www.epa.gov/lead or contact 

your health care provider. 

(2) Community water systems. In addition to including the elements specified in paragraph (a)(1) of this 

section, community water systems must: 

(i) Tell consumers how to get their water tested. 

(ii) Discuss lead in plumbing components and the difference between low lead and lead free. 

(b) Delivery of public education materials. (1) For public water systems serving a large proportion of nonEnglish speaking consumers, as determined by the State, the public education materials must contain 

information in the appropriate language(s) regarding the importance of the notice or contain a telephone 

number or address where persons served may contact the water system to obtain a translated copy of 

the public education materials or to request assistance in the appropriate language. 

(2) A community water system that exceeds the lead action level on the basis of tap water samples 

collected in accordance with §141.86, and that is not already conducting public education tasks under 

this section, must conduct the public education tasks under this section within 60 days after the end of 

the monitoring period in which the exceedance occurred: 

(i) Deliver printed materials meeting the content requirements of paragraph (a) of this section to all bill 

paying customers. 

(ii)(A) Contact customers who are most at risk by delivering education materials that meet the content 

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requirements of paragraph (a) of this section to local public health agencies even if they are not located 

within the water system's service area, along with an informational notice that encourages distribution to 

all the organization's potentially affected customers or community water system's users. The water 

system must contact the local public health agencies directly by phone or in person. The local public 

health agencies may provide a specific list of additional community based organizations serving target 

populations, which may include organizations outside the service area of the water system. If such lists 

are provided, systems must deliver education materials that meet the content requirements of paragraph 

(a) of this section to all organizations on the provided lists. 

(B) Contact customers who are most at risk by delivering materials that meet the content requirements 

of paragraph (a) of this section to the following organizations listed in 1 through 6 that are located within 

the water system's service area, along with an informational notice that encourages distribution to all the 

organization's potentially affected customers or community water system's users: 

( 1 ) Public and private schools or school boards. 

( 2 ) Women, Infants and Children (WIC) and Head Start programs. 

( 3 ) Public and private hospitals and medical clinics. 

( 4 ) Pediatricians. 

( 5 ) Family planning clinics. 

( 6 ) Local welfare agencies. 

(C) Make a good faith effort to locate the following organizations within the service area and deliver 

materials that meet the content requirements of paragraph (a) of this section to them, along with an 

informational notice that encourages distribution to all potentially affected customers or users. The good 

faith effort to contact at-risk customers may include requesting a specific contact list of these 

organizations from the local public health agencies, even if the agencies are not located within the water 

system's service area: 

( 1 ) Licensed childcare centers 

( 2 ) Public and private preschools. 

( 3 ) Obstetricians-Gynecologists and Midwives. 

(iii) No less often than quarterly, provide information on or in each water bill as long as the system 

exceeds the action level for lead. The message on the water bill must include the following statement 

exactly as written except for the text in brackets for which the water system must include system-specific 

information: [INSERT NAME OF WATER SYSTEM] found high levels of lead in drinking water in some 

homes. Lead can cause serious health problems. For more information please call [INSERT NAME OF 

WATER SYSTEM] [or visit (INSERT YOUR WEB SITE HERE)]. The message or delivery mechanism 

can be modified in consultation with the State; specifically, the State may allow a separate mailing of 

public education materials to customers if the water system cannot place the information on water bills. 

(iv) Post material meeting the content requirements of paragraph (a) of this section on the water 

system's Web site if the system serves a population greater than 100,000. 

(v) Submit a press release to newspaper, television and radio stations. 

(vi) In addition to paragraphs (b)(2)(i) through (v) of this section, systems must implement at least three 

activities from one or more categories listed below. The educational content and selection of these 

activities must be determined in consultation with the State. 

(A) Public Service Announcements. 

(B) Paid advertisements. 

(C) Public Area Information Displays. 

(D) E-mails to customers. 

(E) Public Meetings. 

(F) Household Deliveries. 

(G) Targeted Individual Customer Contact. 

(H) Direct material distribution to all multi-family homes and institutions. 

(I) Other methods approved by the State. 

(vii) For systems that are required to conduct monitoring annually or less frequently, the end of the 

monitoring period is September 30 of the calendar year in which the sampling occurs, or, if the State has 

established an alternate monitoring period, the last day of that period. 

(3) As long as a community water system exceeds the action level, it must repeat the activities pursuant 

to paragraph (b)(2) of this section as described in paragraphs (b)(3)(i) through (iv) of this section. 

(i) A community water system shall repeat the tasks contained in paragraphs (b)(2)(i), (ii) and (vi) of this 

section every 12 months. 

(ii) A community water system shall repeat tasks contained in paragraph (b)(2)(iii) of this section with 

each billing cycle. 

(iii) A community water system serving a population greater than 100,000 shall post and retain material 

on a publicly accessible Web site pursuant to paragraph (b)(2)(iv) of this section. 

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(iv) The community water system shall repeat the task in paragraph (b)(2)(v) of this section twice every 

12 months on a schedule agreed upon with the State. The State can allow activities in paragraph (b)(2) 

of this section to extend beyond the 60-day requirement if needed for implementation purposes on a 

case-by-case basis; however, this extension must be approved in writing by the State in advance of the 

60-day deadline. 

(4) Within 60 days after the end of the monitoring period in which the exceedance occurred (unless it 

already is repeating public education tasks pursuant to paragraph (b)(5) of this section), a non-transient 

non-community water system shall deliver the public education materials specified by paragraph (a) of 

this section as follows: 

(i) Post informational posters on lead in drinking water in a public place or common area in each of the 

buildings served by the system; and 

(ii) Distribute informational pamphlets and/or brochures on lead in drinking water to each person served 

by the non-transient non-community water system. The State may allow the system to utilize electronic 

transmission in lieu of or combined with printed materials as long as it achieves at least the same 

coverage. 

(iii) For systems that are required to conduct monitoring annually or less frequently, the end of the 

monitoring period is September 30 of the calendar year in which the sampling occurs, or, if the State has 

established an alternate monitoring period, the last day of that period. 

(5) A non-transient non-community water system shall repeat the tasks contained in paragraph (b)(4) of 

this section at least once during each calendar year in which the system exceeds the lead action level. 

The State can allow activities in (b)(4) of this section to extend beyond the 60-day requirement if needed 

for implementation purposes on a case-by-case basis; however, this extension must be approved in 

writing by the State in advance of the 60-day deadline. 

(6) A water system may discontinue delivery of public education materials if the system has met the lead 

action level during the most recent six-month monitoring period conducted pursuant to §141.86. Such a 

system shall recommence public education in accordance with this section if it subsequently exceeds 

the lead action level during any monitoring period. 

(7) A community water system may apply to the State, in writing (unless the State has waived the 

requirement for prior State approval), to use only the text specified in paragraph (a)(1) of this section in 

lieu of the text in paragraphs (a)(1) and (a)(2) of this section and to perform the tasks listed in 

paragraphs (b)(4) and (b)(5) of this section in lieu of the tasks in paragraphs (b)(2) and (b)(3) of this 

section if: 

(i) The system is a facility, such as a prison or a hospital, where the population served is not capable of 

or is prevented from making improvements to plumbing or installing point of use treatment devices; and 

(ii) The system provides water as part of the cost of services provided and does not separately charge 

for water consumption. 

(8) A community water system serving 3,300 or fewer people may limit certain aspects of their public 

education programs as follows: 

(i) With respect to the requirements of paragraph (b)(2)(vi) of this section, a system serving 3,300 or 

fewer must implement at least one of the activities listed in that paragraph. 

(ii) With respect to the requirements of paragraph (b)(2)(ii) of this section, a system serving 3,300 or 

fewer people may limit the distribution of the public education materials required under that paragraph to 

facilities and organizations served by the system that are most likely to be visited regularly by pregnant 

women and children. 

(iii) With respect to the requirements of paragraph (b)(2)(v) of this section, the State may waive this 

requirement for systems serving 3,300 or fewer persons as long as system distributes notices to every 

household served by the system. 

(c) Supplemental monitoring and notification of results. A water system that fails to meet the lead action 

level on the basis of tap samples collected in accordance with §141.86 shall offer to sample the tap 

water of any customer who requests it. The system is not required to pay for collecting or analyzing the 

sample, nor is the system required to collect and analyze the sample itself. 

(d) Notification of results —(1) Reporting requirement. All water systems must provide a notice of the 

individual tap results from lead tap water monitoring carried out under the requirements of §141.86 to the 

persons served by the water system at the specific sampling site from which the sample was taken (e.g., 

the occupants of the residence where the tap was tested). 

(2) Timing of notification. A water system must provide the consumer notice as soon as practical, but no 

later than 30 days after the system learns of the tap monitoring results. 

(3) Content. The consumer notice must include the results of lead tap water monitoring for the tap that 

was tested, an explanation of the health effects of lead, list steps consumers can take to reduce 

exposure to lead in drinking water and contact information for the water utility. The notice must also 

provide the maximum contaminant level goal and the action level for lead and the definitions for these 

two terms from §141.153(c). 

(4) Delivery. The consumer notice must be provided to persons served at the tap that was tested, either 

by mail or by another method approved by the State. For example, upon approval by the State, a nontransient non-community water system could post the results on a bulletin board in the facility to allow 

users to review the information. The system must provide the notice to customers at sample taps tested, 

including consumers who do not receive water bills. 

[72 FR 57815, Oct. 10, 2007] 

§ 141.86 Monitoring requirements for lead and copper in tap water. 

 top

(a) Sample site location. (1) By the applicable date for commencement of monitoring under paragraph 

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(d)(1) of this section, each water system shall complete a materials evaluation of its distribution system 

in order to identify a pool of targeted sampling sites that meets the requirements of this section, and 

which is sufficiently large to ensure that the water system can collect the number of lead and copper tap 

samples required in paragraph (c) of this section. All sites from which first draw samples are collected 

shall be selected from this pool of targeted sampling sites. Sampling sites may not include faucets that 

have point-of-use or point-of-entry treatment devices designed to remove inorganic contaminants. 

(2) A water system shall use the information on lead, copper, and galvanized steel that it is required to 

collect under §141.42(d) of this part [special monitoring for corrosivity characteristics] when conducting a 

materials evaluation. When an evaluation of the information collected pursuant to §141.42(d) is 

insufficient to locate the requisite number of lead and copper sampling sites that meet the targeting 

criteria in paragraph (a) of this section, the water system shall review the sources of information listed 

below in order to identify a sufficient number of sampling sites. In addition, the system shall seek to 

collect such information where possible in the course of its normal operations (e.g., checking service line 

materials when reading water meters or performing maintenance activities): 

(i) All plumbing codes, permits, and records in the files of the building department(s) which indicate the 

plumbing materials that are installed within publicly and privately owned structures connected to the 

distribution system; 

(ii) All inspections and records of the distribution system that indicate the material composition of the 

service connections that connect a structure to the distribution system; and 

(iii) All existing water quality information, which includes the results of all prior analyses of the system or 

individual structures connected to the system, indicating locations that may be particularly susceptible to 

high lead or copper concentrations. 

(3) The sampling sites selected for a community water system's sampling pool (“tier l sampling sites”) 

shall consist of single family structures that: 

(i) Contain copper pipes with lead solder installed after 1982 or contain lead pipes; and/or 

(ii) Are served by a lead service line. When multiple-family residences comprise at least 20 percent of 

the structures served by a water system, the system may include these types of structures in its 

sampling pool. 

(4) Any community water system with insufficient tier 1 sampling sites shall complete its sampling pool 

with “tier 2 sampling sites”, consisting of buildings, including multiple-family residences that: 

(i) Contain copper pipes with lead solder installed after 1982 or contain lead pipes; and/or 

(ii) Are served by a lead service line. 

(5) Any community water system with insufficient tier 1 and tier 2 sampling sites shall complete its 

sampling pool with “tier 3 sampling sites”, consisting of single family structures that contain copper pipes 

with lead solder installed before 1983. A community water system with insufficient tier 1, tier 2, and tier 3 

sampling sites shall complete its sampling pool with representative sites throughout the distribution 

system. For the purpose of this paragraph, a representative site is a site in which the plumbing materials 

used at that site would be commonly found at other sites served by the water system. 

(6) The sampling sites selected for a non-transient noncommunity water system (“tier l sampling sites”) 

shall consist of buildings that: 

(i) Contain copper pipes with lead solder installed after 1982 or contain lead pipes; and/or 

(ii) Are served by a lead service line. 

(7) A non-transient non-community water system with insufficient tier 1 sites that meet the targeting 

criteria in paragraph (a)(6) of this section shall complete its sampling pool with sampling sites that 

contain copper pipes with lead solder installed before 1983. If additional sites are needed to complete 

the sampling pool, the non-transient non-community water system shall use representative sites 

throughout the distribution system. For the purpose of this paragraph, a representative site is a site in 

which the plumbing materials used at that site would be commonly found at other sites served by the 

water system. 

(8) Any water system whose distribution system contains lead service lines shall draw 50 percent of the 

samples it collects during each monitoring period from sites that contain lead pipes, or copper pipes with 

lead solder, and 50 percent of the samples from sites served by a lead service line. A water system that 

cannot identify a sufficient number of sampling sites served by a lead service line shall collect first-draw 

samples from all of the sites identified as being served by such lines. 

(b) Sample collection methods. (1) All tap samples for lead and copper collected in accordance with this 

subpart, with the exception of lead service line samples collected under §141.84(c) and samples 

collected under paragraph (b)(5) of this section, shall be first-draw samples. 

(2) Each first-draw tap sample for lead and copper shall be one liter in volume and have stood 

motionless in the plumbing system of each sampling site for at least six hours. First-draw samples from 

residential housing shall be collected from the cold water kitchen tap or bathroom sink tap. First-draw 

samples from a nonresidential building shall be one liter in volume and shall be collected at an interior 

tap from which water is typically drawn for consumption. Non-first-draw samples collected in lieu of firstdraw samples pursuant to paragraph (b)(5) of this section shall be one liter in volume and shall be 

collected at an interior tap from which water is typically drawn for consumption. First-draw samples may 

be collected by the system or the system may allow residents to collect first-draw samples after 

instructing the residents of the sampling procedures specified in this paragraph. To avoid problems of 

residents handling nitric acid, acidification of first-draw samples may be done up to 14 days after the 

sample is collected. After acidification to resolubilize the metals, the sample must stand in the original 

container for the time specified in the approved EPA method before the sample can be analyzed. If a 

system allows residents to perform sampling, the system may not challenge, based on alleged errors in 

sample collection, the accuracy of sampling results. 

(3) Each service line sample shall be one liter in volume and have stood motionless in the lead service 

line for at least six hours. Lead service line samples shall be collected in one of the following three ways: 

(i) At the tap after flushing the volume of water between the tap and the lead service line. The volume of 

water shall be calculated based on the interior diameter and length of the pipe between the tap and the 

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lead service line; 

(ii) Tapping directly into the lead service line; or 

(iii) If the sampling site is a building constructed as a single-family residence, allowing the water to run 

until there is a significant change in temperature which would be indicative of water that has been 

standing in the lead service line. 

(4) A water system shall collect each first draw tap sample from the same sampling site from which it 

collected a previous sample. If, for any reason, the water system cannot gain entry to a sampling site in 

order to collect a follow-up tap sample, the system may collect the follow-up tap sample from another 

sampling site in its sampling pool as long as the new site meets the same targeting criteria, and is within 

reasonable proximity of the original site. 

(5) A non-transient non-community water system, or a community water system that meets the criteria of 

§141.85(b)(7), that does not have enough taps that can supply first-draw samples, as defined in §141.2, 

may apply to the State in writing to substitute non-first-draw samples. Such systems must collect as 

many first-draw samples from appropriate taps as possible and identify sampling times and locations 

that would likely result in the longest standing time for the remaining sites. The State has the discretion 

to waive the requirement for prior State approval of non-first-draw sample sites selected by the system, 

either through State regulation or written notification to the system. 

(c) Number of samples. Water systems shall collect at least one sample during each monitoring period 

specified in paragraph (d) of this section from the number of sites listed in the first column (“standard 

monitoring”) of the table in this paragraph. A system conducting reduced monitoring under paragraph (d)

(4) of this section shall collect at least one sample from the number of sites specified in the second 

column (“reduced monitoring”) of the table in this paragraph during each monitoring period specified in 

paragraph (d)(4) of this section. Such reduced monitoring sites shall be representative of the sites 

required for standard monitoring. A public water system that has fewer than five drinking water taps, that 

can be used for human consumption meeting the sample site criteria of paragraph (a) of this section to 

reach the required number of sample sites listed in paragraph (c) of this section, must collect at least 

one sample from each tap and then must collect additional samples from those taps on different days 

during the monitoring period to meet the required number of sites. Alternatively the State may allow 

these public water systems to collect a number of samples less than the number of sites specified in 

paragraph (c) of this section, provided that 100 percent of all taps that can be used for human 

consumption are sampled. The State must approve this reduction of the minimum number of samples in 

writing based on a request from the system or onsite verification by the State. States may specify 

sampling locations when a system is conducting reduced monitoring. The table is as follows: 

(d) Timing of monitoring— (1) Initial tap sampling. 

The first six-month monitoring period for small, medium-size and large systems shall begin on the 

following dates: 

(i) All large systems shall monitor during two consecutive six-month periods. 

(ii) All small and medium-size systems shall monitor during each six-month monitoring period until: 

(A) The system exceeds the lead or copper action level and is therefore required to implement the 

corrosion control treatment requirements under §141.81, in which case the system shall continue 

monitoring in accordance with paragraph (d)(2) of this section, or 

(B) The system meets the lead and copper action levels during two consecutive six-month monitoring 

periods, in which case the system may reduce monitoring in accordance with paragraph (d)(4) of this 

section. 

(2) Monitoring after installation of corrosion control and source water treatment. (i) Any large system 

which installs optimal corrosion control treatment pursuant to §141.81(d)(4) shall monitor during two 

consecutive six-month monitoring periods by the date specified in §141.81(d)(5). 

(ii) Any small or medium-size system which installs optimal corrosion control treatment pursuant to 

§141.81(e)(5) shall monitor during two consecutive six-month monitoring periods by the date specified in 

§141.81(e)(6). 

(iii) Any system which installs source water treatment pursuant to §141.83(a)(3) shall monitor during two 

consecutive six-month monitoring periods by the date specified in §141.83(a)(4). 

(3) Monitoring after State specifies water quality parameter values for optimal corrosion control. After the 

State specifies the values for water quality control parameters under §141.82(f), the system shall 

monitor during each subsequent six-month monitoring period, with the first monitoring period to begin on 

the date the State specifies the optimal values under §141.82(f). 

System size (number of 

people served)

Number of sites 

(standard 

monitoring)

Number of sites 

(reduced 

monitoring)

>100,000 100 50

10,001 to 100,000 60 30

3,301 to 10,000 40 20

501 to 3,300 20 10

101 to 500 10 5

≤100 5 5

System size (No. people 

served)

First six-month monitoring period begins 

on

>50,000 January 1, 1992.

3,301 to 50,000 July 1, 1992.

≤3,300 July 1, 1993.

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(4) Reduced monitoring. (i) A small or medium-size water system that meets the lead and copper action 

levels during each of two consecutive six-month monitoring periods may reduce the number of samples 

in accordance with paragraph (c) of this section, and reduce the frequency of sampling to once per year. 

A small or medium water system collecting fewer than five samples as specified in paragraph (c) of this 

section, that meets the lead and copper action levels during each of two consecutive six-month 

monitoring periods may reduce the frequency of sampling to once per year. In no case can the system 

reduce the number of samples required below the minimum of one sample per available tap. This 

sampling shall begin during the calendar year immediately following the end of the second consecutive 

six-month monitoring period. 

(ii) Any water system that meets the lead action level and maintains the range of values for the water 

quality control parameters reflecting optimal corrosion control treatment specified by the State under 

§141.82(f) during each of two consecutive six-month monitoring periods may reduce the frequency of 

monitoring to once per year and reduce the number of lead and copper samples in accordance with 

paragraph (c) of this section if it receives written approval from the State. This sampling shall begin 

during the calendar year immediately following the end of the second consecutive six-month monitoring 

period. The State shall review monitoring, treatment, and other relevant information submitted by the 

water system in accordance with §141.90, and shall notify the system in writing when it determines the 

system is eligible to commence reduced monitoring pursuant to this paragraph. The State shall review, 

and where appropriate, revise its determination when the system submits new monitoring or treatment 

data, or when other data relevant to the number and frequency of tap sampling becomes available. 

(iii) A small or medium-size water system that meets the lead and copper action levels during three 

consecutive years of monitoring may reduce the frequency of monitoring for lead and copper from 

annually to once every three years. Any water system that meets the lead action level and maintains the 

range of values for the water quality control parameters reflecting optimal corrosion control treatment 

specified by the State under §141.82(f) during three consecutive years of monitoring may reduce the 

frequency of monitoring from annually to once every three years if it receives written approval from the 

State. Samples collected once every three years shall be collected no later than every third calendar 

year. The State shall review monitoring, treatment, and other relevant information submitted by the water 

system in accordance with §141.90, and shall notify the system in writing when it determines the system 

is eligible to reduce the frequency of monitoring to once every three years. The State shall review, and 

where appropriate, revise its determination when the system submits new monitoring or treatment data, 

or when other data relevant to the number and frequency of tap sampling becomes available. 

(iv) A water system that reduces the number and frequency of sampling shall collect these samples from 

representative sites included in the pool of targeted sampling sites identified in paragraph (a) of this 

section. Systems sampling annually or less frequently shall conduct the lead and copper tap sampling 

during the months of June, July, August, or September unless the State has approved a different 

sampling period in accordance with paragraph (d)(4)(iv)(A) of this section. 

(A) The State, at its discretion, may approve a different period for conducting the lead and copper tap 

sampling for systems collecting a reduced number of samples. Such a period shall be no longer than 

four consecutive months and must represent a time of normal operation where the highest levels of lead 

are most likely to occur. For a non-transient non-community water system that does not operate during 

the months of June through September, and for which the period of normal operation where the highest 

levels of lead are most likely to occur is not known, the State shall designate a period that represents a 

time of normal operation for the system. This sampling shall begin during the period approved or 

designated by the State in the calendar year immediately following the end of the second consecutive 

six-month monitoring period for systems initiating annual monitoring and during the three-year period 

following the end of the third consecutive calendar year of annual monitoring for systems initiating 

triennial monitoring. 

(B) Systems monitoring annually, that have been collecting samples during the months of June through 

September and that receive State approval to alter their sample collection period under paragraph (d)(4)

(iv)(A) of this section, must collect their next round of samples during a time period that ends no later 

than 21 months after the previous round of sampling. Systems monitoring triennially that have been 

collecting samples during the months of June through September, and receive State approval to alter 

the sampling collection period as per paragraph (d)(4)(iv)(A) of this section, must collect their next round 

of samples during a time period that ends no later than 45 months after the previous round of sampling. 

Subsequent rounds of sampling must be collected annually or triennially, as required by this section. 

Small systems with waivers, granted pursuant to paragraph (g) of this section, that have been collecting 

samples during the months of June through September and receive State approval to alter their sample 

collection period under paragraph (d)(4)(iv)(A) of this section must collect their next round of samples 

before the end of the 9-year period. 

(v) Any water system that demonstrates for two consecutive 6-month monitoring periods that the tap 

water lead level computed under §141.80(c)(3) is less than or equal to 0.005 mg/L and the tap water 

copper level computed under §141.80(c)(3) is less than or equal to 0.65 mg/L may reduce the number of 

samples in accordance with paragraph (c) of this section and reduce the frequency of sampling to once 

every three calendar years. 

(vi)(A) A small or medium-size water system subject to reduced monitoring that exceeds the lead or 

copper action level shall resume sampling in accordance with paragraph (d)(3) of this section and collect 

the number of samples specified for standard monitoring under paragraph (c) of this section. Such a 

system shall also conduct water quality parameter monitoring in accordance with §141.87(b), (c) or (d) 

(as appropriate) during the monitoring period in which it exceeded the action level. Any such system 

may resume annual monitoring for lead and copper at the tap at the reduced number of sites specified in 

paragraph (c) of this section after it has completed two subsequent consecutive six-month rounds of 

monitoring that meet the criteria of paragraph (d)(4)(i) of this section and/or may resume triennial 

monitoring for lead and copper at the reduced number of sites after it demonstrates through subsequent 

rounds of monitoring that it meets the criteria of either paragraph (d)(4)(iii) or (d)(4)(v) of this section. 

(B) Any water system subject to the reduced monitoring frequency that fails to meet the lead action level 

during any four-month monitoring period or that fails to operate at or above the minimum value or within 

the range of values for the water quality parameters specified by the State under §141.82(f) for more 

than nine days in any six-month period specified in §141.87(d) shall conduct tap water sampling for lead 

and copper at the frequency specified in paragraph (d)(3) of this section, collect the number of samples 

specified for standard monitoring under paragraph (c) of this section, and shall resume monitoring for 

water quality parameters within the distribution system in accordance with §141.87(d). This standard tap 

water sampling shall begin no later than the six-month period beginning January 1 of the calendar year 

following the lead action level exceedance or water quality parameter excursion. Such a system may 

resume reduced monitoring for lead and copper at the tap and for water quality parameters within the 

distribution system under the following conditions: 

( 1 ) The system may resume annual monitoring for lead and copper at the tap at the reduced number of 

sites specified in paragraph (c) of this section after it has completed two subsequent six-month rounds of 

monitoring that meet the criteria of paragraph (d)(4)(ii) of this section and the system has received 

written approval from the State that it is appropriate to resume reduced monitoring on an annual 

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frequency. This sampling shall begin during the calendar year immediately following the end of the 

second consecutive six-month monitoring period. 

( 2 ) The system may resume triennial monitoring for lead and copper at the tap at the reduced number 

of sites after it demonstrates through subsequent rounds of monitoring that it meets the criteria of either 

paragraph (d)(4)(iii) or (d)(4)(v) of this section and the system has received written approval from the 

State that it is appropriate to resume triennial monitoring. 

( 3 ) The system may reduce the number of water quality parameter tap water samples required in 

accordance with §141.87(e)(1) and the frequency with which it collects such samples in accordance with 

§141.87(e)(2). Such a system may not resume triennial monitoring for water quality parameters at the 

tap until it demonstrates, in accordance with the requirements of §141.87(e)(2), that it has re-qualified for 

triennial monitoring. 

(vii) Any water system subject to a reduced monitoring frequency under paragraph (d)(4) of this section 

shall notify the State in writing in accordance with §141.90(a)(3) of any upcoming long-term change in 

treatment or addition of a new source as described in that section. The State must review and approve 

the addition of a new source or long-term change in water treatment before it is implemented by the 

water system. The State may require the system to resume sampling in accordance with paragraph (d)

(3) of this section and collect the number of samples specified for standard monitoring under paragraph 

(c) of this section or take other appropriate steps such as increased water quality parameter monitoring 

or re-evaluation of its corrosion control treatment given the potentially different water quality 

considerations. 

(e) Additional monitoring by systems. The results of any monitoring conducted in addition to the 

minimum requirements of this section shall be considered by the system and the State in making any 

determinations ( i.e. , calculating the 90th percentile lead or copper level) under this subpart. 

(f) Invalidation of lead or copper tap water samples. A sample invalidated under this paragraph does not 

count toward determining lead or copper 90th percentile levels under §141.80(c)(3) or toward meeting 

the minimum monitoring requirements of paragraph (c) of this section. 

(1) The State may invalidate a lead or copper tap water sample at least if one of the following conditions 

is met. 

(i) The laboratory establishes that improper sample analysis caused erroneous results. 

(ii) The State determines that the sample was taken from a site that did not meet the site selection 

criteria of this section. 

(iii) The sample container was damaged in transit. 

(iv) There is substantial reason to believe that the sample was subject to tampering. 

(2) The system must report the results of all samples to the State and all supporting documentation for 

samples the system believes should be invalidated. 

(3) To invalidate a sample under paragraph (f)(1) of this section, the decision and the rationale for the 

decision must be documented in writing. States may not invalidate a sample solely on the grounds that a 

follow-up sample result is higher or lower than that of the original sample. 

(4) The water system must collect replacement samples for any samples invalidated under this section 

if, after the invalidation of one or more samples, the system has too few samples to meet the minimum 

requirements of paragraph (c) of this section. Any such replacement samples must be taken as soon as 

possible, but no later than 20 days after the date the State invalidates the sample or by the end of the 

applicable monitoring period, whichever occurs later. Replacement samples taken after the end of the 

applicable monitoring period shall not also be used to meet the monitoring requirements of a subsequent 

monitoring period. The replacement samples shall be taken at the same locations as the invalidated 

samples or, if that is not possible, at locations other than those already used for sampling during the 

monitoring period. 

(g) Monitoring waivers for small systems. Any small system that meets the criteria of this paragraph may 

apply to the State to reduce the frequency of monitoring for lead and copper under this section to once 

every nine years ( i.e., a “full waiver”) if it meets all of the materials criteria specified in paragraph (g)(1) 

of this section and all of the monitoring criteria specified in paragraph (g)(2) of this section. If State 

regulations permit, any small system that meets the criteria in paragraphs (g)(1) and (2) of this section 

only for lead, or only for copper, may apply to the State for a waiver to reduce the frequency of tap water 

monitoring to once every nine years for that contaminant only ( i.e., a “partial waiver”). 

(1) Materials criteria. The system must demonstrate that its distribution system and service lines and all 

drinking water supply plumbing, including plumbing conveying drinking water within all residences and 

buildings connected to the system, are free of lead-containing materials and/or copper-containing 

materials, as those terms are defined in this paragraph, as follows: 

(i) Lead. To qualify for a full waiver, or a waiver of the tap water monitoring requirements for lead ( i.e., a 

“lead waiver”), the water system must provide certification and supporting documentation to the State 

that the system is free of all lead-containing materials, as follows: 

(A) It contains no plastic pipes which contain lead plasticizers, or plastic service lines which contain lead 

plasticizers; and 

(B) It is free of lead service lines, lead pipes, lead soldered pipe joints, and leaded brass or bronze alloy 

fittings and fixtures, unless such fittings and fixtures meet the specifications of any standard established 

pursuant to 42 U.S.C. 300g–6(e) (SDWA section 1417(e)). 

(ii) Copper. To qualify for a full waiver, or a waiver of the tap water monitoring requirements for copper 

( i.e., a “copper waiver”), the water system must provide certification and supporting documentation to 

the State that the system contains no copper pipes or copper service lines. 

(2) Monitoring criteria for waiver issuance. The system must have completed at least one 6-month round 

of standard tap water monitoring for lead and copper at sites approved by the State and from the 

number of sites required by paragraph (c) of this section and demonstrate that the 90th percentile levels 

for any and all rounds of monitoring conducted since the system became free of all lead-containing 

and/or copper-containing materials, as appropriate, meet the following criteria. 

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(i) Lead levels. To qualify for a full waiver, or a lead waiver, the system must demonstrate that the 90th 

percentile lead level does not exceed 0.005 mg/L. 

(ii) Copper levels. To qualify for a full waiver, or a copper waiver, the system must demonstrate that the 

90th percentile copper level does not exceed 0.65 mg/L. 

(3) State approval of waiver application. The State shall notify the system of its waiver determination, in 

writing, setting forth the basis of its decision and any condition of the waiver. As a condition of the 

waiver, the State may require the system to perform specific activities (e.g., limited monitoring, periodic 

outreach to customers to remind them to avoid installation of materials that might void the waiver) to 

avoid the risk of lead or copper concentration of concern in tap water. The small system must continue 

monitoring for lead and copper at the tap as required by paragraphs (d)(1) through (d)(4) of this section, 

as appropriate, until it receives written notification from the State that the waiver has been approved. 

(4) Monitoring frequency for systems with waivers. (i) A system with a full waiver must conduct tap water 

monitoring for lead and copper in accordance with paragraph (d)(4)(iv) of this section at the reduced 

number of sampling sites identified in paragraph (c) of this section at least once every nine years and 

provide the materials certification specified in paragraph (g)(1) of this section for both lead and copper to 

the State along with the monitoring results. Samples collected every nine years shall be collected no 

later than every ninth calendar year. 

(ii) A system with a partial waiver must conduct tap water monitoring for the waived contaminant in 

accordance with paragraph (d)(4)(iv) of this section at the reduced number of sampling sites specified in 

paragraph (c) of this section at least once every nine years and provide the materials certification 

specified in paragraph (g)(1) of this section pertaining to the waived contaminant along with the 

monitoring results. Such a system also must continue to monitor for the non-waived contaminant in 

accordance with requirements of paragraph (d)(1) through (d)(4) of this section, as appropriate. 

(iii) Any water system with a full or partial waiver shall notify the State in writing in accordance with 

§141.90(a)(3) of any upcoming long-term change in treatment or addition of a new source, as described 

in that section. The State must review and approve the addition of a new source or long-term change in 

water treatment before it is implemented by the water system. The State has the authority to require the 

system to add or modify waiver conditions (e.g., require recertification that the system is free of leadcontaining and/or copper-containing materials, require additional round(s) of monitoring), if it deems 

such modifications are necessary to address treatment or source water changes at the system. 

(iv) If a system with a full or partial waiver becomes aware that it is no longer free of lead-containing or 

copper-containing materials, as appropriate, (e.g., as a result of new construction or repairs), the system 

shall notify the State in writing no later than 60 days after becoming aware of such a change. 

(5) Continued eligibility. If the system continues to satisfy the requirements of paragraph (g)(4) of this 

section, the waiver will be renewed automatically, unless any of the conditions listed in paragraph (g)(5)

(i) through (g)(5)(iii) of this section occurs. A system whose waiver has been revoked may re-apply for a 

waiver at such time as it again meets the appropriate materials and monitoring criteria of paragraphs (g)

(1) and (g)(2) of this section. 

(i) A system with a full waiver or a lead waiver no longer satisfies the materials criteria of paragraph (g)

(1)(i) of this section or has a 90th percentile lead level greater than 0.005 mg/L. 

(ii) A system with a full waiver or a copper waiver no longer satisfies the materials criteria of paragraph 

(g)(1)(ii) of this section or has a 90th percentile copper level greater than 0.65 mg/L. 

(iii) The State notifies the system, in writing, that the waiver has been revoked, setting forth the basis of 

its decision. 

(6) Requirements following waiver revocation. A system whose full or partial waiver has been revoked by 

the State is subject to the corrosion control treatment and lead and copper tap water monitoring 

requirements, as follows: 

(i) If the system exceeds the lead and/or copper action level, the system must implement corrosion 

control treatment in accordance with the deadlines specified in §141.81(e), and any other applicable 

requirements of this subpart. 

(ii) If the system meets both the lead and the copper action level, the system must monitor for lead and 

copper at the tap no less frequently than once every three years using the reduced number of sample 

sites specified in paragraph (c) of this section. 

(7) Pre-existing waivers. Small system waivers approved by the State in writing prior to April 11, 2000 

shall remain in effect under the following conditions: 

(i) If the system has demonstrated that it is both free of lead-containing and copper-containing materials, 

as required by paragraph (g)(1) of this section and that its 90th percentile lead levels and 90th percentile 

copper levels meet the criteria of paragraph (g)(2) of this section, the waiver remains in effect so long as 

the system continues to meet the waiver eligibility criteria of paragraph (g)(5) of this section. The first 

round of tap water monitoring conducted pursuant to paragraph (g)(4) of this section shall be completed 

no later than nine years after the last time the system has monitored for lead and copper at the tap. 

(ii) If the system has met the materials criteria of paragraph (g)(1) of this section but has not met the 

monitoring criteria of paragraph (g)(2) of this section, the system shall conduct a round of monitoring for 

lead and copper at the tap demonstrating that it meets the criteria of paragraph (g)(2) of this section no 

later than September 30, 2000. Thereafter, the waiver shall remain in effect as long as the system meets 

the continued eligibility criteria of paragraph (g)(5) of this section. The first round of tap water monitoring 

conducted pursuant to paragraph (g)(4) of this section shall be completed no later than nine years after 

the round of monitoring conducted pursuant to paragraph (g)(2) of this section. 

[56 FR 26548, June 7, 1991; 56 FR 32113, July 15, 1991; 57 FR 28788, June 29, 1992; as amended at 

65 FR 2007, Jan. 12, 2000; 72 FR 57817, Oct. 10, 2007] 

§ 141.87 Monitoring requirements for water quality parameters. 

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All large water systems, and all small- and medium-size systems that exceed the lead or copper action 

level shall monitor water quality parameters in addition to lead and copper in accordance with this 

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section. The requirements of this section are summarized in the table at the end of this section. 

(a) General requirements —(1) Sample collection methods. (i) Tap samples shall be representative of 

water quality throughout the distribution system taking into account the number of persons served, the 

different sources of water, the different treatment methods employed by the system, and seasonal 

variability. Tap sampling under this section is not required to be conducted at taps targeted for lead and 

copper sampling under §141.86(a). [Note: Systems may find it convenient to conduct tap sampling for 

water quality parameters at sites used for coliform sampling under 40 CFR 141.21.] 

(ii) Samples collected at the entry point(s) to the distribution system shall be from locations 

representative of each source after treatment. If a system draws water from more than one source and 

the sources are combined before distribution, the system must sample at an entry point to the 

distribution system during periods of normal operating conditions ( i.e. , when water is representative of 

all sources being used). 

(2) Number of samples. (i) Systems shall collect two tap samples for applicable water quality parameters 

during each monitoring period specified under paragraphs (b) through (e) of this section from the 

following number of sites. 

(ii) Except as provided in paragraph (c)(3) of this section, systems shall collect two samples for each 

applicable water quality parameter at each entry point to the distribution system during each monitoring 

period specified in paragraph (b) of this section. During each monitoring period specified in paragraphs 

(c)–(e) of this section, systems shall collect one sample for each applicable water quality parameter at 

each entry point to the distribution system. 

(b) Initial sampling All large water systems shall measure the applicable water quality parameters as 

specified below at taps and at each entry point to the distribution system during each six-month 

monitoring period specified in §141.86(d)(1). All small and medium-size systems shall measure the 

applicable water quality parameters at the locations specified below during each six-month monitoring 

period specified in §141.86(d)(1) during which the system exceeds the lead or copper action level. 

(1) At taps: 

(i) pH; 

(ii) Alkalinity; 

(iii) Orthophosphate, when an inhibitor containing a phosphate compound is used; 

(iv) Silica, when an inhibitor containing a silicate compound is used; 

(v) Calcium; 

(vi) Conductivity; and 

(vii) Water temperature. 

(2) At each entry point to the distribution system: all of the applicable parameters listed in paragraph (b)

(1) of this section. 

(c) Monitoring after installation of corrosion control. Any large system which installs optimal corrosion 

control treatment pursuant to §141.81(d)(4) shall measure the water quality parameters at the locations 

and frequencies specified below during each six-month monitoring period specified in §141.86(d)(2)(i). 

Any small or medium-size system which installs optimal corrosion control treatment shall conduct such 

monitoring during each six-month monitoring period specified in §141.86(d)(2)(ii) in which the system 

exceeds the lead or copper action level. 

(1) At taps, two samples for: 

(i) pH; 

(ii) Alkalinity; 

(iii) Orthophosphate, when an inhibitor containing a phosphate compound is used; 

(iv) Silica, when an inhibitor containing a silicate compound is used; 

(v) Calcium, when calcium carbonate stabilization is used as part of corrosion control. 

(2) Except as provided in paragraph (c)(3) of this section, at each entry point to the distribution system, 

at least one sample no less frequently than every two weeks (biweekly) for: 

(i) pH; 

(ii) When alkalinity is adjusted as part of optimal corrosion control, a reading of the dosage rate of the 

chemical used to adjust alkalinity, and the alkalinity concentration; and 

(iii) When a corrosion inhibitor is used as part of optimal corrosion control, a reading of the dosage rate 

System size (No. people 

served)

No. of sites for water quality 

parameters

>100,000 25

10,001–100,000 10

3,301 to 10,000 3

501 to 3,300 2

101 to 500 1

≤100 1

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of the inhibitor used, and the concentration of orthophosphate or silica (whichever is applicable). 

(3) Any ground water system can limit entry point sampling described in paragraph (c)(2) of this section 

to those entry points that are representative of water quality and treatment conditions throughout the 

system. If water from untreated ground water sources mixes with water from treated ground water 

sources, the system must monitor for water quality parameters both at representative entry points 

receiving treatment and representative entry points receiving no treatment. Prior to the start of any 

monitoring under this paragraph, the system shall provide to the State written information identifying the 

selected entry points and documentation, including information on seasonal variability, sufficient to 

demonstrate that the sites are representative of water quality and treatment conditions throughout the 

system. 

(d) Monitoring after State specifies water quality parameter values for optimal corrosion control . After 

the State specifies the values for applicable water quality control parameters reflecting optimal corrosion 

control treatment under §141.82(f), all large systems shall measure the applicable water quality 

parameters in accordance with paragraph (c) of this section and determine compliance with the 

requirements of §141.82(g) every six months with the first six-month period to begin on either January 1 

or July 1, whichever comes first, after the State specifies the optimal values under §141.82(f). Any small 

or medium-size system shall conduct such monitoring during each six-month period specified in this 

paragraph in which the system exceeds the lead or copper action level. For any such small and mediumsize system that is subject to a reduced monitoring frequency pursuant to §141.86(d)(4) at the time of 

the action level exceedance, the start of the applicable six-month monitoring period under this paragraph 

shall coincide with the start of the applicable monitoring period under §141.86(d)(4). Compliance with 

State-designated optimal water quality parameter values shall be determined as specified under §141.82

(g). 

(e) Reduced monitoring. (1) Any water system that maintains the range of values for the water quality 

parameters reflecting optimal corrosion control treatment during each of two consecutive six-month 

monitoring periods under paragraph (d) of this section shall continue monitoring at the entry point(s) to 

the distribution system as specified in paragraph (c)(2) of this section. Such system may collect two tap 

samples for applicable water quality parameters from the following reduced number of sites during each 

six-month monitoring period. 

(2)(i) Any water system that maintains the range of values for the water quality parameters reflecting 

optimal corrosion control treatment specified by the State under §141.82(f) during three consecutive 

years of monitoring may reduce the frequency with which it collects the number of tap samples for 

applicable water quality parameters specified in this paragraph (e)(1) of this section from every six 

months to annually. This sampling begins during the calendar year immediately following the end of the 

monitoring period in which the third consecutive year of six-month monitoring occurs. Any water system 

that maintains the range of values for the water quality parameters reflecting optimal corrosion control 

treatment specified by the State under §141.82(f), during three consecutive years of annual monitoring 

under this paragraph may reduce the frequency with which it collects the number of tap samples for 

applicable water quality parameters specified in paragraph (e)(1) of this section from annually to every 

three years. This sampling begins no later than the third calendar year following the end of the 

monitoring period in which the third consecutive year of monitoring occurs. 

(ii) A water system may reduce the frequency with which it collects tap samples for applicable water 

quality parameters specified in paragraph (e)(1) of this section to every three years if it demonstrates 

during two consecutive monitoring periods that its tap water lead level at the 90th percentile is less than 

or equal to the PQL for lead specified in §141.89 (a)(1)(ii), that its tap water copper level at the 90th 

percentile is less than or equal to 0.65 mg/L for copper in §141.80(c)(2), and that it also has maintained 

the range of values for the water quality parameters reflecting optimal corrosion control treatment 

specified by the State under §141.82(f). Monitoring conducted every three years shall be done no later 

than every third calendar year. 

(3) A water system that conducts sampling annually shall collect these samples evenly throughout the 

year so as to reflect seasonal variability. 

(4) Any water system subject to the reduced monitoring frequency that fails to operate at or above the 

minimum value or within the range of values for the water quality parameters specified by the State in 

§141.82(f) for more than nine days in any six-month period specified in §141.82(g) shall resume 

distribution system tap water sampling in accordance with the number and frequency requirements in 

paragraph (d) of this section. Such a system may resume annual monitoring for water quality parameters 

at the tap at the reduced number of sites specified in paragraph (e)(1) of this section after it has 

completed two subsequent consecutive six-month rounds of monitoring that meet the criteria of that 

paragraph and/or may resume triennial monitoring for water quality parameters at the tap at the reduced 

number of sites after it demonstrates through subsequent rounds of monitoring that it meets the criteria 

of either paragraph (e)(2)(i) or (e)(2)(ii) of this section. 

(f) Additional monitoring by systems. The results of any monitoring conducted in addition to the minimum 

requirements of this section shall be considered by the system and the State in making any 

determinations ( i.e. , determining concentrations of water quality parameters) under this section or 

§141.82. 

Summary of Monitoring Requirements for Water Quality Parameters1

System size (No. of people 

served)

Reduced No. of sites for water quality 

parameters

>100,000 10

10,001 to 100,000 7

3,301 to 10,000 3

501 to 3,300 2

101 to 500 1

≤100 1

Monitoring 

period Parameters2 Location Frequency

Initial monitoring pH, alkalinity, 

orthophosphate or silica3, 

calcium, conductivity, 

Taps and at 

entry point(s) 

to distribution 

Every 6 months.

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1Table is for illustrative purposes; consult the text of this section for precise regulatory requirements.

2Small and medium-size systems have to monitor for water quality parameters only during monitoring 

periods in which the system exceeds the lead or copper action level. 

3Orthophosphate must be measured only when an inhibitor containing a phosphate compound is used. 

Silica must be measured only when an inhibitor containing silicate compound is used. 

4Calcium must be measured only when calcium carbonate stabilization is used as part of corrosion 

control. 

5Inhibitor dosage rates and inhibitor residual concentrations (orthophosphate or silica) must be 

measured only when an inhibitor is used. 

6Ground water systems may limit monitoring to representative locations throughout the system.

7Water systems may reduce frequency of monitoring for water quality parameters at the tap from every 

six months to annually if they have maintained the range of values for water quality parameters reflecting 

optimal corrosion control during 3 consecutive years of monitoring. 

8Water systems may further reduce the frequency of monitoring for water quality parameters at the tap 

from annually to once every 3 years if they have maintained the range of values for water quality 

parameters reflecting optimal corrosion control during 3 consecutive years of annual monitoring. Water 

systems may accelerate to triennial monitoring for water quality parameters at the tap if they have 

maintained 90th percentile lead levels less than or equal to 0.005 mg/L, 90th percentile copper levels 

less than or equal to 0.65 mg/L, and the range of water quality parameters designated by the State 

under §141.82(f) as representing optimal corrosion control during two consecutive six-month monitoring 

periods. 

[56 FR 26548, June 7, 1991; 57 FR 28788, June 29, 1992, as amended at 59 FR 33862, June 30, 1994; 

65 FR 2010, Jan. 12, 2000; 72 FR 57818, Oct. 10, 2007] 

§ 141.88 Monitoring requirements for lead and copper in source water. 

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(a) Sample location, collection methods, and number of samples. (1) A water system that fails to meet 

the lead or copper action level on the basis of tap samples collected in accordance with §141.86 shall 

collect lead and copper source water samples in accordance with the following requirements regarding 

sample location, number of samples, and collection methods: 

(i) Groundwater systems shall take a minimum of one sample at every entry point to the distribution 

system which is representative of each well after treatment (hereafter called a sampling point). The 

system shall take one sample at the same sampling point unless conditions make another sampling 

point more representative of each source or treatment plant. 

temperature system

After installation 

of corrosion 

control

pH, alkalinity, 

orthophosphate or silica3, 

calcium4

Taps Every 6 months.

 pH, alkalinity, dosage rate 

and concentration (if 

alkalinity adjusted as part 

of corrosion control), 

inhibitor dosage rate and 

inhibitor residual5

Entry point(s) 

to distribution 

system6

No less 

frequently than 

every two 

weeks.

After State 

specifies 

parameter 

values for 

optimal 

corrosion control

pH, alkalinity, 

orthophosphate or silica3, 

calcium4

Taps Every 6 months.

 pH, alkalinity dosage rate 

and concentration (if 

alkalinity adjusted as part 

of corrosion control), 

inhibitor dosage rate and 

inhibitor residual5

Entry point(s) 

to distribution 

system6

No less 

frequently than 

every two 

weeks.

Reduced 

monitoring

pH, alkalinity, 

orthophosphate or silica3, 

calcium4

Taps Every 6 months, 

annually7or 

every 3 years8; 

reduced number 

of sites.

 pH, alkalinity dosage rate 

and concentration (if 

alkalinity adjusted as part 

of corrosion control), 

inhibitor dosage rate and 

inhibitor residual5

Entry point(s) 

to distribution 

system6

No less 

frequently than 

every two 

weeks.

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(ii) Surface water systems shall take a minimum of one sample at every entry point to the distribution 

system after any application of treatment or in the distribution system at a point which is representative 

of each source after treatment (hereafter called a sampling point). The system shall take each sample at 

the same sampling point unless conditions make another sampling point more representative of each 

source or treatment plant. 

Note to paragraph (a)(1)(ii): For the purposes of this paragraph, surface water systems 

include systems with a combination of surface and ground sources.

(iii) If a system draws water from more than one source and the sources are combined before 

distribution, the system must sample at an entry point to the distribution system during periods of normal 

operating conditions ( i.e., when water is representative of all sources being used). 

(iv) The State may reduce the total number of samples which must be analyzed by allowing the use of 

compositing. Compositing of samples must be done by certified laboratory personnel. Composite 

samples from a maximum of five samples are allowed, provided that if the lead concentration in the 

composite sample is greater than or equal to 0.001 mg/L or the copper concentration is greater than or 

equal to 0.160 mg/L, then either: 

(A) A follow-up sample shall be taken and analyzed within 14 days at each sampling point included in 

the composite; or 

(B) If duplicates of or sufficient quantities from the original samples from each sampling point used in the 

composite are available, the system may use these instead of resampling. 

(2) Where the results of sampling indicate an exceedance of maximum permissible source water levels 

established under §141.83(b)(4), the State may require that one additional sample be collected as soon 

as possible after the initial sample was taken (but not to exceed two weeks) at the same sampling point. 

If a State-required confirmation sample is taken for lead or copper, then the results of the initial and 

confirmation sample shall be averaged in determining compliance with the State-specified maximum 

permissible levels. Any sample value below the detection limit shall be considered to be zero. Any value 

above the detection limit but below the PQL shall either be considered as the measured value or be 

considered one-half the PQL. 

(b) Monitoring frequency after system exceeds tap water action level. Any system which exceeds the 

lead or copper action level at the tap shall collect one source water sample from each entry point to the 

distribution system no later than six months after the end of the monitoring period during which the lead 

or copper action level was exceeded. For monitoring periods that are annual or less frequent, the end of 

the monitoring period is September 30 of the calendar year in which the sampling occurs, or if the State 

has established an alternate monitoring period, the last day of that period. 

(c) Monitoring frequency after installation of source water treatment. Any system which installs source 

water treatment pursuant to §141.83(a)(3) shall collect an additional source water sample from each 

entry point to the distribution system during two consecutive six-month monitoring periods by the 

deadline specified in §141.83(a)(4). 

(d) Monitoring frequency after State specifies maximum permissible source water levels or determines 

that source water treatment is not needed. (1) A system shall monitor at the frequency specified below in 

cases where the State specifies maximum permissible source water levels under §141.83(b)(4) or 

determines that the system is not required to install source water treatment under §141.83(b)(2). 

(i) A water system using only groundwater shall collect samples once during the three-year compliance 

period (as that term is defined in §141.2) in effect when the applicable State determination under 

paragraph (d)(1) of this section is made. Such systems shall collect samples once during each 

subsequent compliance period. Triennial samples shall be collected every third calendar year. 

(ii) A water system using surface water (or a combination of surface and ground water) shall collect 

samples once during each calendar year, the first annual monitoring period to begin during the year in 

which the applicable State determination is made under paragraph (d)(1) of this section. 

(2) A system is not required to conduct source water sampling for lead and/or copper if the system 

meets the action level for the specific contaminant in tap water samples during the entire source water 

sampling period applicable to the system under paragraph (d)(1) (i) or (ii) of this section. 

(e) Reduced monitoring frequency. (1) A water system using only ground water may reduce the 

monitoring frequency for lead and copper in source water to once during each nine-year compliance 

cycle (as that term is defined in §141.2) provided that the samples are collected no later than every ninth 

calendar year and if the system meets one of the following criteria: 

(i) The system demonstrates that finished drinking water entering the distribution system has been 

maintained below the maximum permissible lead and copper concentrations specified by the State in 

§141.83(b)(4) during at least three consecutive compliance periods under paragraph (d)(1) of this 

section; or 

(ii) The State has determined that source water treatment is not needed and the system demonstrates 

that, during at least three consecutive compliance periods in which sampling was conducted under 

paragraph (d)(1) of this section, the concentration of lead in source water was less than or equal to 

0.005 mg/L and the concentration of copper in source water was less than or equal to 0.65 mg/L. 

(2) A water system using surface water (or a combination of surface water and ground water) may 

reduce the monitoring frequency in paragraph (d)(1) of this section to once during each nine-year 

compliance cycle (as that term is defined in §141.2) provided that the samples are collected no later 

than every ninth calendar year and if the system meets one of the following criteria: 

(i) The system demonstrates that finished drinking water entering the distribution system has been 

maintained below the maximum permissible lead and copper concentrations specified by the State in 

§141.83(b)(4) for at least three consecutive years; or 

(ii) The State has determined that source water treatment is not needed and the system demonstrates 

that, during at least three consecutive years, the concentration of lead in source water was less than or 

equal to 0.005 mg/L and the concentration of copper in source water was less than or equal to 0.65 

mg/L. 

(3) A water system that uses a new source of water is not eligible for reduced monitoring for lead and/or 

copper until concentrations in samples collected from the new source during three consecutive 

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monitoring periods are below the maximum permissible lead and copper concentrations specified by the 

State in §141.83(a)(5). 

[56 FR 26548, June 7, 1991; 57 FR 28788 and 28789, June 29, 1992, as amended at 65 FR 2012, Jan. 

12, 2000; 72 FR 57819, Oct. 10, 2007] 

§ 141.89 Analytical methods. 

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(a) Analyses for lead, copper, pH, conductivity, calcium, alkalinity, orthophosphate, silica, and 

temperature shall be conducted with the methods in §141.23(k)(1). 

(1) Analyses for alkalinity, calcium, conductivity, orthophosphate, pH, silica, and temperature may be 

performed by any person acceptable to the State. Analyses under this section for lead and copper shall 

only be conducted by laboratories that have been certified by EPA or the State. To obtain certification to 

conduct analyses for lead and copper, laboratories must: 

(i) Analyze Performance Evaluation samples, which include lead and copper, provided by or acceptable 

to EPA or the State at least once a year by each method for which the laboratory desires certification; 

and 

(ii) Achieve quantitative acceptance limits as follows: 

(A) For lead: ±30 percent of the actual amount in the Performance Evaluation sample when the actual 

amount is greater than or equal to 0.005 mg/L. The Practical Quantitation Level, or PQL for lead is 0.005 

mg/L. 

(B) For Copper: ±10 percent of the actual amount in the Performance Evaluation sample when the 

actual amount is greater than or equal to 0.050 mg/L. The Practical Quantitation Level, or PQL for 

copper is 0.050 mg/L. 

(iii) Achieve the method detection limit for lead of 0.001 mg/L according to the procedures in appendix B 

of part 136 of this title. This need only be accomplished if the laboratory will be processing source water 

composite samples under §141.88(a)(1)(iv). 

(iv) Be currently certified by EPA or the State to perform analyses to the specifications described in 

paragraph (a)(1) of this section. 

(2) States have the authority to allow the use of previously collected monitoring data for purposes of 

monitoring, if the data were collected and analyzed in accordance with the requirements of this subpart. 

(3) All lead and copper levels measured between the PQL and MDL must be either reported as 

measured or they can be reported as one-half the PQL specified for lead and copper in paragraph (a)(1)

(ii) of this section. All levels below the lead and copper MDLs must be reported as zero. 

(4) All copper levels measured between the PQL and the MDL must be either reported as measured or 

they can be reported as one-half the PQL (0.025 mg/L). All levels below the copper MDL must be 

reported as zero. 

(b) [Reserved] 

[56 FR 26548, June 7, 1991, as amended at 57 FR 28789, June 29, 1992; 57 FR 31847, July 17, 1992; 

59 FR 33863, June 30, 1994; 59 FR 62470, Dec. 5, 1994; 64 FR 67466, Dec. 1, 1999; 65 FR 2012, Jan. 

12, 2000; 72 FR 57819, Oct. 10, 2007] 

§ 141.90 Reporting requirements. 

 top

All water systems shall report all of the following information to the State in accordance with this section. 

(a) Reporting requirements for tap water monitoring for lead and copper and for water quality parameter 

monitoring. (1) Except as provided in paragraph (a)(1)(viii) of this section, a water system shall report the 

information specified below for all tap water samples specified in §141.86 and for all water quality 

parameter samples specified in §141.87 within the first 10 days following the end of each applicable 

monitoring period specified in §141.86 and §141.87 ( i.e., every six months, annually, every 3 years, or 

every 9 years). For monitoring periods with a duration less than six months, the end of the monitoring 

period is the last date samples can be collected during that period as specified in §§141.86 and 141.87. 

(i) The results of all tap samples for lead and copper including the location of each site and the criteria 

under §141.86(a) (3), (4), (5), (6), and/or (7) under which the site was selected for the system's sampling 

pool; 

(ii) Documentation for each tap water lead or copper sample for which the water system requests 

invalidation pursuant to §141.86(f)(2); 

(iii) [Reserved] 

(iv) The 90th percentile lead and copper concentrations measured from among all lead and copper tap 

water samples collected during each monitoring period (calculated in accordance with §141.80(c)(3)), 

unless the State calculates the system's 90th percentile lead and copper levels under paragraph (h) of 

this section; 

(v) With the exception of initial tap sampling conducted pursuant to §141.86(d)(1), the system shall 

designate any site which was not sampled during previous monitoring periods, and include an 

explanation of why sampling sites have changed; 

(vi) The results of all tap samples for pH, and where applicable, alkalinity, calcium, conductivity, 

temperature, and orthophosphate or silica collected under §141.87 (b)–(e); 

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(vii) The results of all samples collected at the entry point(s) to the distribution system for applicable 

water quality parameters under §141.87 (b)–(e); 

(viii) A water system shall report the results of all water quality parameter samples collected under 

§141.87(c) through (f) during each six-month monitoring period specified in §141.87(d) within the first 10 

days following the end of the monitoring period unless the State has specified a more frequent reporting 

requirement. 

(2) For a non-transient non-community water system, or a community water system meeting the criteria 

of §141.85(b)(7), that does not have enough taps that can provide first-draw samples, the system must 

either: 

(i) Provide written documentation to the State identifying standing times and locations for enough nonfirst-draw samples to make up its sampling pool under §141.86(b)(5) by the start of the first applicable 

monitoring period under §141.86(d) that commences after April 11, 2000, unless the State has waived 

prior State approval of non-first-draw sample sites selected by the system pursuant to §141.86(b)(5); or 

(ii) If the State has waived prior approval of non-first-draw sample sites selected by the system, identify, 

in writing, each site that did not meet the six-hour minimum standing time and the length of standing time 

for that particular substitute sample collected pursuant to §141.86(b)(5) and include this information with 

the lead and copper tap sample results required to be submitted pursuant to paragraph (a)(1)(i) of this 

section. 

(3) At a time specified by the State, or if no specific time is designated by the State, then as early as 

possible prior to the addition of a new source or any long-term change in water treatment, a water 

system deemed to have optimized corrosion control under §141.81(b)(3), a water system subject to 

reduced monitoring pursuant to §141.86(d)(4), or a water system subject to a monitoring waiver 

pursuant to §141.86(g), shall submit written documentation to the State describing the change or 

addition. The State must review and approve the addition of a new source or long-term change in 

treatment before it is implemented by the water system. Examples of long-term treatment changes 

include the addition of a new treatment process or modification of an existing treatment process. 

Examples of modifications include switching secondary disinfectants, switching coagulants (e.g., alum to 

ferric chloride), and switching corrosion inhibitor products (e.g., orthophosphate to blended phosphate). 

Long-term changes can include dose changes to existing chemicals if the system is planning long-term 

changes to its finished water pH or residual inhibitor concentration. Long-term treatment changes would 

not include chemical dose fluctuations associated with daily raw water quality changes. 

(4) Any small system applying for a monitoring waiver under §141.86(g), or subject to a waiver granted 

pursuant to §141.86(g)(3), shall provide the following information to the State in writing by the specified 

deadline: 

(i) By the start of the first applicable monitoring period in §141.86(d), any small water system applying for 

a monitoring waiver shall provide the documentation required to demonstrate that it meets the waiver 

criteria of §§141.86(g)(1) and (2). 

(ii) No later than nine years after the monitoring previously conducted pursuant to §141.86(g)(2) or 

§141.86(g)(4)(i), each small system desiring to maintain its monitoring waiver shall provide the 

information required by §§141.86(g)(4)(i) and (ii). 

(iii) No later than 60 days after it becomes aware that it is no longer free of lead-containing and/or 

copper-containing material, as appropriate, each small system with a monitoring waiver shall provide 

written notification to the State, setting forth the circumstances resulting in the lead-containing and/or 

copper-containing materials being introduced into the system and what corrective action, if any, the 

system plans to remove these materials. 

(iv) By October 10, 2000, any small system with a waiver granted prior to April 11, 2000 and that has not 

previously met the requirements of §141.86(g)(2) shall provide the information required by that 

paragraph. 

(5) Each ground water system that limits water quality parameter monitoring to a subset of entry points 

under §141.87(c)(3) shall provide, by the commencement of such monitoring, written correspondence to 

the State that identifies the selected entry points and includes information sufficient to demonstrate that 

the sites are representative of water quality and treatment conditions throughout the system. 

(b) Source water monitoring reporting requirements. (1) A water system shall report the sampling results 

for all source water samples collected in accordance with §141.88 within the first 10 days following the 

end of each source water monitoring period ( i.e. , annually, per compliance period, per compliance 

cycle) specified in §141.88. 

(2) With the exception of the first round of source water sampling conducted pursuant to §141.88(b), the 

system shall specify any site which was not sampled during previous monitoring periods, and include an 

explanation of why the sampling point has changed. 

(c) Corrosion control treatment reporting requirements. By the applicable dates under §141.81, systems 

shall report the following information: 

(1) For systems demonstrating that they have already optimized corrosion control, information required 

in §141.81(b) (2) or (3). 

(2) For systems required to optimize corrosion control, their recommendation regarding optimal 

corrosion control treatment under §141.82(a). 

(3) For systems required to evaluate the effectiveness of corrosion control treatments under §141.82(c), 

the information required by that paragraph. 

(4) For systems required to install optimal corrosion control designated by the State under §141.82(d), a 

letter certifying that the system has completed installing that treatment. 

(d) Source water treatment reporting requirements. By the applicable dates in §141.83, systems shall 

provide the following information to the State: 

(1) If required under §141.83(b)(1), their recommendation regarding source water treatment; 

(2) For systems required to install source water treatment under §141.83(b)(2), a letter certifying that the 

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system has completed installing the treatment designated by the State within 24 months after the State 

designated the treatment. 

(e) Lead service line replacement reporting requirements. Systems shall report the following information 

to the State to demonstrate compliance with the requirements of §141.84: 

(1) No later than 12 months after the end of a monitoring period in which a system exceeds the lead 

action level in sampling referred to in §141.84(a), the system must submit written documentation to the 

State of the material evaluation conducted as required in §141.86(a), identify the initial number of lead 

service lines in its distribution system at the time the system exceeds the lead action level, and provide 

the system's schedule for annually replacing at least 7 percent of the initial number of lead service lines 

in its distribution system. 

(2) No later than 12 months after the end of a monitoring period in which a system exceeds the lead 

action level in sampling referred to in §141.84(a), and every 12 months thereafter, the system shall 

demonstrate to the State in writing that the system has either: 

(i) Replaced in the previous 12 months at least 7 percent of the initial lead service lines (or a greater 

number of lines specified by the State under §141.84(e)) in its distribution system, or 

(ii) Conducted sampling which demonstrates that the lead concentration in all service line samples from 

an individual line(s), taken pursuant to §141.86(b)(3), is less than or equal to 0.015 mg/L. In such cases, 

the total number of lines replaced and/or which meet the criteria in §141.84(c) shall equal at least 7 

percent of the initial number of lead lines identified under paragraph (e)(1) of this section (or the 

percentage specified by the State under §141.84(e)). 

(3) The annual letter submitted to the State under paragraph (e)(2) of this section shall contain the 

following information: 

(i) The number of lead service lines scheduled to be replaced during the previous year of the system's 

replacement schedule; 

(ii) The number and location of each lead service line replaced during the previous year of the system's 

replacement schedule; 

(iii) If measured, the water lead concentration and location of each lead service line sampled, the 

sampling method, and the date of sampling. 

(4) Any system which collects lead service line samples following partial lead service line replacement 

required by §141.84 shall report the results to the State within the first ten days of the month following 

the month in which the system receives the laboratory results, or as specified by the State. States, at 

their discretion may eliminate this requirement to report these monitoring results. Systems shall also 

report any additional information as specified by the State, and in a time and manner prescribed by the 

State, to verify that all partial lead service line replacement activities have taken place. 

(f) Public education program reporting requirements. (1) Any water system that is subject to the public 

education requirements in §141.85 shall, within ten days after the end of each period in which the 

system is required to perform public education in accordance with §141.85(b), send written 

documentation to the State that contains: 

(i) A demonstration that the system has delivered the public education materials that meet the content 

requirements in §141.85(a) and the delivery requirements in §141.85(b); and 

(ii) A list of all the newspapers, radio stations, television stations, and facilities and organizations to 

which the system delivered public education materials during the period in which the system was 

required to perform public education tasks. 

(2) Unless required by the State, a system that previously has submitted the information required by 

paragraph (f)(1)(ii) of this section need not resubmit the information required by paragraph (f)(1)(ii) of 

this section, as long as there have been no changes in the distribution list and the system certifies that 

the public education materials were distributed to the same list submitted previously. 

(3) No later than 3 months following the end of the monitoring period, each system must mail a sample 

copy of the consumer notification of tap results to the State along with a certification that the notification 

has been distributed in a manner consistent with the requirements of §141.85(d). 

(g) Reporting of additional monitoring data. Any system which collects sampling data in addition to that 

required by this subpart shall report the results to the State within the first ten days following the end of 

the applicable monitoring period under §§141.86, 141.87 and 141.88 during which the samples are 

collected. 

(h) Reporting of 90th percentile lead and copper concentrations where the State calculates a system's 

90th percentile concentrations. A water system is not required to report the 90th percentile lead and 

copper concentrations measured from among all lead and copper tap water samples collected during 

each monitoring period, as required by paragraph (a)(1)(iv) of this section if: 

(1) The State has previously notified the water system that it will calculate the water system's 90th 

percentile lead and copper concentrations, based on the lead and copper tap results submitted pursuant 

to paragraph (h)(2)(i) of this section, and has specified a date before the end of the applicable 

monitoring period by which the system must provide the results of lead and copper tap water samples; 

(2) The system has provided the following information to the State by the date specified in paragraph (h)

(1) of this section: 

(i) The results of all tap samples for lead and copper including the location of each site and the criteria 

under §141.86(a)(3), (4), (5), (6), and/or (7) under which the site was selected for the system's sampling 

pool, pursuant to paragraph (a)(1)(i) of this section; and 

(ii) An identification of sampling sites utilized during the current monitoring period that were not sampled 

during previous monitoring periods, and an explanation why sampling sites have changed; and 

(3) The State has provided the results of the 90th percentile lead and copper calculations, in writing, to 

the water system before the end of the monitoring period. 

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[56 FR 26548, June 7, 1991; 57 FR 28789, June 29, 1992, as amended at 59 FR 33864, June 30, 1994; 

65 FR 2012, Jan. 12, 2000; 72 FR 57819, Oct. 10, 2007] 

§ 141.91 Recordkeeping requirements. 

 top

Any system subject to the requirements of this subpart shall retain on its premises original records of all 

sampling data and analyses, reports, surveys, letters, evaluations, schedules, State determinations, and 

any other information required by §§141.81 through 141.88. Each water system shall retain the records 

required by this section for no fewer than 12 years. 

Subpart J—Use of Non-Centralized Treatment Devices 

 top

Source: 52 FR 25716, July 8, 1987, unless otherwise noted. 

§ 141.100 Criteria and procedures for public water systems using point-of-entry 

devices. 

 top

(a) Public water systems may use point-of-entry devices to comply with maximum contaminant levels 

only if they meet the requirements of this section. 

(b) It is the responsibility of the public water system to operate and maintain the point-of-entry treatment 

system. 

(c) The public water system must develop and obtain State approval for a monitoring plan before pointof-entry devices are installed for compliance. Under the plan approved by the State, point-of-entry 

devices must provide health protection equivalent to central water treatment. “Equivalent” means that 

the water would meet all national primary drinking water regulations and would be of acceptable quality 

similar to water distributed by a well-operated central treatment plant. In addition to the VOCs, 

monitoring must include physical measurements and observations such as total flow treated and 

mechanical condition of the treatment equipment. 

(d) Effective technology must be properly applied under a plan approved by the State and the 

microbiological safety of the water must be maintained. 

(1) The State must require adequate certification of performance, field testing, and, if not included in the 

certification process, a rigorous engineering design review of the point-of-entry devices. 

(2) The design and application of the point-of-entry devices must consider the tendency for increase in 

heterotrophic bacteria concentrations in water treated with activated carbon. It may be necessary to use 

frequent backwashing, post-contactor disinfection, and Heterotrophic Plate Count monitoring to ensure 

that the microbiological safety of the water is not compromised. 

(e) All consumers shall be protected. Every building connected to the system must have a point-of-entry 

device installed, maintained, and adequately monitored. The State must be assured that every building 

is subject to treatment and monitoring, and that the rights and responsibilities of the public water system 

customer convey with title upon sale of property. 

[52 FR 25716, July 8, 1987; 53 FR 25111, July 1, 1988] 

§ 141.101 Use of bottled water. 

 top

Public water systems shall not use bottled water to achieve compliance with an MCL. Bottled water may 

be used on a temporary basis to avoid unreasonable risk to health. 

[63 FR 31934, June 11, 1998] 

Subpart K—Treatment Techniques 

 top

Source: 56 FR 3594, Jan. 30, 1991, unless otherwise noted. 

§ 141.110 General requirements. 

 top

The requirements of subpart K of this part constitute national primary drinking water regulations. These 

regulations establish treatment techniques in lieu of maximum contaminant levels for specified 

contaminants. 

§ 141.111 Treatment techniques for acrylamide and epichlorohydrin. 

 top

Each public water system must certify annually in writing to the State (using third party or manufacturer's 

certification) that when acrylamide and epichlorohydrin are used in drinking water systems, the 

combination (or product) of dose and monomer level does not exceed the levels specified as follows: 

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Acrylamide=0.05% dosed at 1 ppm (or equivalent) 

Epichlorohydrin=0.01% dosed at 20 ppm (or equivalent) 

Certifications can rely on manufacturers or third parties, as approved by the State. 

Subpart L—Disinfectant Residuals, Disinfection Byproducts, and Disinfection 

Byproduct Precursors 

 top

§ 141.130 General requirements. 

 top

(a) The requirements of this subpart L constitute national primary drinking water regulations. 

(1) The regulations in this subpart establish criteria under which community water systems (CWSs) and 

nontransient, noncommunity water systems (NTNCWSs) which add a chemical disinfectant to the water 

in any part of the drinking water treatment process must modify their practices to meet MCLs and 

MRDLs in §§141.64 and 141.65, respectively, and must meet the treatment technique requirements for 

disinfection byproduct precursors in §141.135. 

(2) The regulations in this subpart establish criteria under which transient NCWSs that use chlorine 

dioxide as a disinfectant or oxidant must modify their practices to meet the MRDL for chlorine dioxide in 

§141.65. 

(3) EPA has established MCLs for TTHM and HAA5 and treatment technique requirements for 

disinfection byproduct precursors to limit the levels of known and unknown disinfection byproducts which 

may have adverse health effects. These disinfection byproducts may include chloroform; 

bromodichloromethane; dibromochloromethane; bromoform; dichloroacetic acid; and trichloroacetic acid. 

(b) Compliance dates —(1) CWSs and NTNCWSs. Unless otherwise noted, systems must comply with 

the requirements of this subpart as follows. Subpart H systems serving 10,000 or more persons must 

comply with this subpart beginning January 1, 2002. Subpart H systems serving fewer than 10,000 

persons and systems using only ground water not under the direct influence of surface water must 

comply with this subpart beginning January 1, 2004. 

(2) Transient NCWSs. Subpart H systems serving 10,000 or more persons and using chlorine dioxide as 

a disinfectant or oxidant must comply with any requirements for chlorine dioxide in this subpart 

beginning January 1, 2002. Subpart H systems serving fewer than 10,000 persons and using chlorine 

dioxide as a disinfectant or oxidant and systems using only ground water not under the direct influence 

of surface water and using chlorine dioxide as a disinfectant or oxidant must comply with any 

requirements for chlorine dioxide in this subpart beginning January 1, 2004. 

(c) Each CWS and NTNCWS regulated under paragraph (a) of this section must be operated by 

qualified personnel who meet the requirements specified by the State and are included in a State 

register of qualified operators. 

(d) Control of disinfectant residuals. Notwithstanding the MRDLs in §141.65, systems may increase 

residual disinfectant levels in the distribution system of chlorine or chloramines (but not chlorine dioxide) 

to a level and for a time necessary to protect public health, to address specific microbiological 

contamination problems caused by circumstances such as, but not limited to, distribution line breaks, 

storm run-off events, source water contamination events, or cross-connection events. 

[63 FR 69466, Dec. 16, 1998, as amended at 66 FR 3776, Jan. 16, 2001] 

§ 141.131 Analytical requirements. 

 top

(a) General. (1) Systems must use only the analytical methods specified in this section, or their 

equivalent as approved by EPA, to demonstrate compliance with the requirements of this subpart and 

with the requirements of subparts U and V of this part. These methods are effective for compliance 

monitoring February 16, 1999, unless a different effective date is specified in this section or by the State. 

(2) The following documents are incorporated by reference. The Director of the Federal Register 

approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies 

may be inspected at EPA's Drinking Water Docket, 1301 Constitution Avenue, NW., EPA West, Room 

B102, Washington, DC 20460, or at the National Archives and Records Administration (NARA). For 

information on the availability of this material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. EPA Method 

552.1 is in Methods for the Determination of Organic Compounds in Drinking Water-Supplement II, 

USEPA, August 1992, EPA/600/R–92/129 (available through National Information Technical Service 

(NTIS), PB92–207703). EPA Methods 502.2, 524.2, 551.1, and 552.2 are in Methods for the 

Determination of Organic Compounds in Drinking Water-Supplement III, USEPA, August 1995, 

EPA/600/R–95/131 (available through NTIS, PB95–261616). EPA Method 300.0 is in Methods for the 

Determination of Inorganic Substances in Environmental Samples, USEPA, August 1993, EPA/600/R–

93/100 (available through NTIS, PB94–121811). EPA Methods 300.1 and 321.8 are in Methods for the 

Determination of Organic and Inorganic Compounds in Drinking Water, Volume 1, USEPA, August 2000, 

EPA 815–R–00–014 (available through NTIS, PB2000–106981). EPA Method 317.0, Revision 2.0, 

“Determination of Inorganic Oxyhalide Disinfection By-Products in Drinking Water Using Ion 

Chromatography with the Addition of a Postcolumn Reagent for Trace Bromate Analysis,” USEPA, July 

2001, EPA 815–B–01–001, EPA Method 326.0, Revision 1.0, “Determination of Inorganic Oxyhalide 

Disinfection By-Products in Drinking Water Using Ion Chromatography Incorporating the Addition of a 

Suppressor Acidified Postcolumn Reagent for Trace Bromate Analysis,” USEPA, June 2002, EPA 815–

R–03–007, EPA Method 327.0, Revision 1.1, “Determination of Chlorine Dioxide and Chlorite Ion in 

Drinking Water Using Lissamine Green B and Horseradish Peroxidase with Detection by Visible 

Spectrophotometry,” USEPA, May 2005, EPA 815–R–05–008 and EPA Method 552.3, Revision 1.0, 

“Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-liquid Microextraction, 

Derivatization, and Gas Chromatography with Electron Capture Detection,” USEPA, July 2003, EPA–

815–B–03–002 can be accessed and downloaded directly on-line at 

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http://www.epa.gov/safewater/methods/sourcalt.html. EPA Method 415.3, Revision 1.1, “Determination 

of Total Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water,” 

USEPA, February 2005, EPA/600/R–05/055 can be accessed and downloaded directly on-line at 

www.epa.gov/nerlcwww/ordmeth.htm. Standard Methods 4500–Cl D, 4500–Cl E, 4500–Cl F, 4500–Cl G, 

4500–Cl H, 500–Cl I, 4500–ClO2D, 4500–ClO2E, 6251 B, and 5910 B shall be followed in accordance 

with Standard Methods for the Examination of Water and Wastewater, 19th or 20th Editions, American 

Public Health Association, 1995 and 1998, respectively. The cited methods published in either edition 

may be used. Standard Methods 5310 B, 5310 C, and 5310 D shall be followed in accordance with the 

Supplement to the 19th Edition of Standard Methods for the Examination of Water and Wastewater, or 

the Standard Methods for the Examination of Water and Wastewater, 20th Edition, American Public 

Health Association, 1996 and 1998, respectively. The cited methods published in either edition may be 

used. Copies may be obtained from the American Public Health Association, 1015 Fifteenth Street, NW., 

Washington, DC 20005. Standard Methods 4500–Cl D–00, 4500–Cl E–00, 4500–Cl F–00, 4500–Cl G–

00, 4500–Cl H–00, 4500–Cl I–00, 4500–ClO2E–00, 6251 B–94, 5310 B–00, 5310 C–00, 5310 D–00 and 

5910 B–00 are available at http://www.standardmethods.org or at EPA's Water Docket. The year in 

which each method was approved by the Standard Methods Committee is designated by the last two 

digits in the method number. The methods listed are the only Online versions that are IBR-approved. 

ASTM Methods D 1253–86 and D 1253–86 (Reapproved 1996) shall be followed in accordance with the 

Annual Book of ASTM Standards, Volume 11.01, American Society for Testing and Materials 

International, 1996 or any ASTM edition containing the IBR-approved version of the method may be 

used. ASTM Method D1253–03 shall be followed in accordance with the Annual Book of ASTM 

Standards, Volume 11.01, American Society for Testing and Materials International, 2004 or any ASTM 

edition containing the IBR-approved version of the method may be used. ASTM Method D 6581–00 shall 

be followed in accordance with the Annual Book of ASTM Standards, Volume 11.01, American Society 

for Testing and Materials International, 2001 or any ASTM edition containing the IBR-approved version 

of the method may be used; copies may be obtained from the American Society for Testing and 

Materials International, 100 Barr Harbor Drive, West Conshohocken, PA 19428–2959. 

(b) Disinfection byproducts. (1) Systems must measure disinfection byproducts by the methods (as 

modified by the footnotes) listed in the following table or one of the alternative methods listed in 

appendix A to subpart C of this part: 

Approved Methods for Disinfection Byproduct Compliance Monitoring 

1P&T = purge and trap; GC = gas chromatography; ElCD = electrolytic conductivity detector; PID = 

photoionization detector; MS = mass spectrometer; LLE = liquid/liquid extraction; ECD = electron 

capture detector; SPE = solid phase extraction; IC = ion chromatography; ICP–MS = inductively coupled 

plasma/mass spectrometer. 

219th and 20th editions of Standard Methods for the Examination of Water and Wastewater, 1995 and 

1998, respectively, American Public Health Association; either of these editions may be used. 

3Annual Book of ASTM Standards, 2001 or any year containing the cited version of the method, Vol 

11.01. 

4If TTHMs are the only analytes being measured in the sample, then a PID is not required.

5The samples must be extracted within 14 days of sample collection.

Contaminant and methodology1

EPA 

method

Standard 

method2

SM 

online9

ASTM 

method3

TTHM

P&T/GC/ElCD & PID 502.24

P&T/GC/MS 524.2

LLE/GC/ECD 551.1

HAA5

LLE 

(diazomethane)/GC/ECD

6251 B5 6251 B–

94

SPE (acidic 

methanol)/GC/ECD

552.15

LLE (acidic 

methanol)/GC/ECD

552.2, 

552.3

Bromate

Ion chromatography 300.1 D 6581–

00

Ion chromatography & 

post column reaction

317.0 Rev 

2.06, 

326.06

IC/ICP–MS 321.86,7

Chlorite

Amperometric titration 4500–

ClO2E8

4500–

ClO2E–

008

Spectrophotometry 327.0 Rev 

1.18

Ion chromatography 300.0, 

300.1, 

317.0 Rev 

2.0, 326.0

D 6581–

00

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6Ion chromatography & post column reaction or IC/ICP-MS must be used for monitoring of bromate for 

purposes of demonstrating eligibility of reduced monitoring, as prescribed in §141.132(b)(3)(ii). 

7Samples must be preserved at the time of sampling with 50 mg ethylenediamine (EDA)/L of sample 

and must be analyzed within 28 days. 

8Amperometric titration or spectrophotometry may be used for routine daily monitoring of chlorite at the 

entrance to the distribution system, as prescribed in §141.132(b)(2)(i)(A). Ion chromatography must be 

used for routine monthly monitoring of chlorite and additional monitoring of chlorite in the distribution 

system, as prescribed in §141.132(b)(2)(i)(B) and (b)(2)(ii). 

9The Standard Methods Online version that is approved is indicated by the last two digits in the method 

number which is the year of approval by the Standard Method Committee. Standard Methods Online are 

available at http://www.standardmethods.org. 

(2) Analyses under this section for disinfection byproducts must be conducted by laboratories that have 

received certification by EPA or the State, except as specified under paragraph (b)(3) of this section. To 

receive certification to conduct analyses for the DBP contaminants in §§141.64, 141.135, and subparts 

U and V of this part, the laboratory must: 

(i) Analyze Performance Evaluation (PE) samples that are acceptable to EPA or the State at least once 

during each consecutive 12 month period by each method for which the laboratory desires certification. 

(ii) Until March 31, 2007, in these analyses of PE samples, the laboratory must achieve quantitative 

results within the acceptance limit on a minimum of 80% of the analytes included in each PE sample. 

The acceptance limit is defined as the 95% confidence interval calculated around the mean of the PE 

study between a maximum and minimum acceptance limit of ±50% and ±15% of the study mean. 

(iii) Beginning April 1, 2007, the laboratory must achieve quantitative results on the PE sample analyses 

that are within the following acceptance limits: 

(iv) Beginning April 1, 2007, report quantitative data for concentrations at least as low as the ones listed 

in the following table for all DBP samples analyzed for compliance with §§141.64, 141.135, and subparts 

U and V of this part: 

DBP

Acceptance 

limits (percent 

of true value) Comments

TTHM

Chloroform ±20 Laboratory must meet all 4 

individual THM acceptance 

limits in order to 

successfully pass a PE 

sample for TTHM

Bromodichloromethane ±20

Dibromochloromethane ±20

Bromoform ±20

HAA5

Monochloroacetic Acid ±40 Laboratory must meet the 

acceptance limits for 4 out 

of 5 of the HAA5 

compounds in order to 

successfully pass a PE 

sample for HAA5

Dichloroacetic Acid ±40

Trichloroacetic Acid ±40

Monobromoacetic Acid ±40

Dibromoacetic Acid ±40

Chlorite ±30

Bromate ±30

DBP

Minimum 

reporting 

level (mg/L)1 Comments

TTHM2

Chloroform 0.0010

Bromodichloromethane 0.0010

Dibromochloromethane 0.0010

Bromoform 0.0010

HAA52

Monochloroacetic Acid 0.0020

Dichloroacetic Acid 0.0010

Trichloroacetic Acid 0.0010

Monobromoacetic Acid 0.0010

Dibromoacetic Acid 0.0010

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1The calibration curve must encompass the regulatory minimum reporting level (MRL) concentration. 

Data may be reported for concentrations lower than the regulatory MRL as long as the precision and 

accuracy criteria are met by analyzing an MRL check standard at the lowest reporting limit chosen by 

the laboratory. The laboratory must verify the accuracy of the calibration curve at the MRL concentration 

by analyzing an MRL check standard with a concentration less than or equal to 110% of the MRL with 

each batch of samples. The measured concentration for the MRL check standard must be ±50% of the 

expected value, if any field sample in the batch has a concentration less than 5 times the regulatory 

MRL. Method requirements to analyze higher concentration check standards and meet tighter 

acceptance criteria for them must be met in addition to the MRL check standard requirement. 

2When adding the individual trihalomethane or haloacetic acid concentrations to calculate the TTHM or 

HAA5 concentrations, respectively, a zero is used for any analytical result that is less than the MRL 

concentration for that DBP, unless otherwise specified by the State. 

(3) A party approved by EPA or the State must measure daily chlorite samples at the entrance to the 

distribution system. 

(c) Disinfectant residuals. (1) Systems must measure residual disinfectant concentration for free 

chlorine, combined chlorine (chloramines), and chlorine dioxide by the methods listed in the following 

table or one of the alternative methods listed in appendix A to subpart C of this part: 

1X indicates method is approved for measuring specified disinfectant residual. Free chlorine or total 

chlorine may be measured for demonstrating compliance with the chlorine MRDL and combined 

chlorine, or total chlorine may be measured for demonstrating compliance with the chloramine MRDL. 

2The Standard Methods Online version that is approved is indicated by the last two digits in the method 

number which is the year of approval by the Standard Method Committee. Standard Methods Online are 

available at http://www.standardmethods.org. 

(2) If approved by the State, systems may also measure residual disinfectant concentrations for chlorine, 

chloramines, and chlorine dioxide by using DPD colorimetric test kits. 

(3) A party approved by EPA or the State must measure residual disinfectant concentration. 

(d) Additional analytical methods. Systems required to analyze parameters not included in paragraphs 

(b) and (c) of this section must use the following methods or one of the alternative methods listed in 

appendix A to subpart C of this part. A party approved by EPA or the State must measure these 

parameters. 

(1) Alkalinity. All methods allowed in §141.89(a) for measuring alkalinity. 

Chlorite 0.020 Applicable to monitoring as 

prescribed in §141.132(b)(2)

(1)(B) and (b)(2)(ii).

Bromate 0.0050 or 

0.0010

Laboratories that use EPA 

Methods 317.0 Revision 2.0, 

326.0 or 321.8 must meet a 

0.0010 mg/L MRL for 

bromate.

Methodology

SM 

(19th 

or 

20th 

ed)

SM 

Online2

ASTM 

method

EPA 

method

Residual measured1

Free

Cl2

Combined

Cl2

Total

Cl2 ClO2

Amperometric 

Titration

4500–

Cl D

4500–

Cl D–

00

D 

1253–

86 (96), 

03

 XX X 

Low Level 

Amperometric 

Titration

4500–

Cl E

4500–

Cl E–00

X

DPD Ferrous 

Titrimetric

4500–

Cl F

4500–

Cl F–00

XX X 

DPD Colorimetric 4500–

Cl G

4500–

Cl G–

00

XX X 

Syringaldazine 

(FACTS)

4500–

Cl H

4500–

Cl H–

00

X 

Iodometric 

Electrode

4500–

Cl I

4500–

Cl I–00

X 

DPD 4500–

ClO2D

X

Amperometric 

Method II

4500–

ClO2E

4500–

ClO2E–

00

X

Lissamine Green 

Spectrophotometric

327.0 

Rev 1.1

X

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(2) Bromide. EPA Methods 300.0, 300.1, 317.0 Revision 2.0, 326.0, or ASTM D 6581–00. 

(3) Total Organic Carbon (TOC). Standard Method 5310 B or 5310 B–00 (High-Temperature 

Combustion Method) or Standard Method 5310 C or 5310 C–00 (Persulfate-Ultraviolet or HeatedPersulfate Oxidation Method) or Standard Method 5310 D or 5310 D–00 (Wet-Oxidation Method) or EPA 

Method 415.3 Revision 1.1. Inorganic carbon must be removed from the samples prior to analysis. TOC 

samples may not be filtered prior to analysis. TOC samples must be acidified at the time of sample 

collection to achieve pH less than or equal to 2 with minimal addition of the acid specified in the method 

or by the instrument manufacturer. Acidified TOC samples must be analyzed within 28 days. 

(4) Specific Ultraviolet Absorbance (SUVA). SUVA is equal to the UV absorption at 254nm (UV254) 

(measured in m-1 divided by the dissolved organic carbon (DOC) concentration (measured as mg/L). In 

order to determine SUVA, it is necessary to separately measure UV254and DOC. When determining 

SUVA, systems must use the methods stipulated in paragraph (d)(4)(i) of this section to measure DOC 

and the method stipulated in paragraph (d)(4)(ii) of this section to measure UV254. SUVA must be 

determined on water prior to the addition of disinfectants/oxidants by the system. DOC and 

UV254samples used to determine a SUVA value must be taken at the same time and at the same 

location. 

(i) Dissolved Organic Carbon (DOC). Standard Method 5310 B or 5310 B–00 (High-Temperature 

Combustion Method) or Standard Method 5310 C or 5310 C–00 (Persulfate-Ultraviolet or HeatedPersulfate Oxidation Method) or Standard Method 5310 D or 5310 D–00 (Wet-Oxidation Method) or EPA 

Method 415.3 Revision 1.1. DOC samples must be filtered through the 0.45 μm pore-diameter filter as 

soon as practical after sampling, not to exceed 48 hours. After filtration, DOC samples must be acidified 

to achieve pH less than or equal to 2 with minimal addition of the acid specified in the method or by the 

instrument manufacturer. Acidified DOC samples must be analyzed within 28 days of sample collection. 

Inorganic carbon must be removed from the samples prior to analysis. Water passed through the filter 

prior to filtration of the sample must serve as the filtered blank. This filtered blank must be analyzed 

using procedures identical to those used for analysis of the samples and must meet the following 

criteria: DOC < 0.5 mg/L. 

(ii) Ultraviolet Absorption at 254 nm (UV254). Standard Method 5910 B or 5910 B–00 (Ultraviolet 

Absorption Method) or EPA Method 415.3 Revision 1.1. UV absorption must be measured at 253.7 nm 

(may be rounded off to 254 nm). Prior to analysis, UV254samples must be filtered through a 0.45 μm 

pore-diameter filter. The pH of UV254samples may not be adjusted. Samples must be analyzed as soon 

as practical after sampling, not to exceed 48 hours. 

(5) pH. All methods allowed in §141.23(k)(1) for measuring pH. 

(6) Magnesium. All methods allowed in §141.23(k)(1) for measuring magnesium. 

[63 FR 69466, Dec. 16, 1998, as amended at 66 FR 3776, Jan. 16, 2001; 71 FR 479, Jan. 4, 2006; 71 

FR 37168, June 29, 2006; 74 FR 30958, June 29, 2009] 

§ 141.132 Monitoring requirements. 

 top

(a) General requirements. (1) Systems must take all samples during normal operating conditions. 

(2) Systems may consider multiple wells drawing water from a single aquifer as one treatment plant for 

determining the minimum number of TTHM and HAA5 samples required, with State approval in 

accordance with criteria developed under §142.16(h)(5) of this chapter. 

(3) Failure to monitor in accordance with the monitoring plan required under paragraph (f) of this section 

is a monitoring violation. 

(4) Failure to monitor will be treated as a violation for the entire period covered by the annual average 

where compliance is based on a running annual average of monthly or quarterly samples or averages 

and the system's failure to monitor makes it impossible to determine compliance with MCLs or MRDLs. 

(5) Systems may use only data collected under the provisions of this subpart to qualify for reduced 

monitoring. 

(b) Monitoring requirements for disinfection byproducts —(1) TTHMs and HAA5 —(i) Routine monitoring. 

Systems must monitor at the frequency indicated in the following table: 

Routine Monitoring Frequency for TTHM and HAA5 

Type of system

Minimum 

monitoring 

frequency

Sample location in the distribution 

system

Subpart H system 

serving at least 

10,000 persons

Four water 

samples per 

quarter per 

treatment plant

At least 25 percent of all samples 

collected each quarter at locations 

representing maximum residence 

time. Remaining samples taken at 

locations representative of at least 

average residence time in the 

distribution system and representing 

the entire distribution system, taking 

into account number of persons 

served, different sources of water, and 

different treatment methods.1

Subpart H system 

serving from 500 to 

One water 

sample per 

Locations representing maximum 

residence time.1

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1If a system elects to sample more frequently than the minimum required, at least 25 percent of all 

samples collected each quarter (including those taken in excess of the required frequency) must be 

taken at locations that represent the maximum residence time of the water in the distribution system. 

The remaining samples must be taken at locations representative of at least average residence time in 

the distribution system. 

2Multiple wells drawing water from a single aquifer may be considered one treatment plant for 

determining the minimum number of samples required, with State approval in accordance with criteria 

developed under §142.16(h)(5) of this chapter. 

(ii) Systems may reduce monitoring, except as otherwise provided, in accordance with the following 

table: 

Reduced Monitoring Frequency for TTHM and HAA5 

9,999 persons quarter per 

treatment plant

Subpart H system 

serving fewer than 

500 persons

One sample per 

year per 

treatment plant 

during month of 

warmest water 

temperature.

Locations representing maximum 

residence time.1If the sample (or 

average of annual samples, if more 

than one sample is taken) exceeds 

the MCL, the system must increase 

monitoring to one sample per 

treatment plant per quarter, taken at a 

point reflecting the maximum 

residence time in the distribution 

system, until the system meets criteria 

in paragraph (b)(1)(iv) of this section.

System using only 

ground water not 

under direct 

influence of surface 

water using 

chemical 

disinfectant and 

serving at least 

10,000 persons

One water 

sample per 

quarter per 

treatment plant2

Locations representing maximum 

residence time.1

System using only 

ground water not 

under direct 

influence of surface 

water using 

chemical 

disinfectant and 

serving fewer than 

10,000 persons

One sample per 

year per 

treatment 

plant2during 

month of 

warmest water 

temperature.

Locations representing maximum 

residence time.1If the sample (or 

average of annual samples, if more 

than one sample is taken) exceeds 

the MCL, the system must increase 

monitoring to one sample per 

treatment plant per quarter, taken at a 

point reflecting the maximum 

residence time in the distribution 

system, until the system meets criteria 

in paragraph (b)(1)(iv) of this section.

If you are a . . .

You may reduce 

monitoring if you have 

monitored at least one 

year and your . . . To this level

Subpart H system 

serving at least 

10,000 persons 

which has a source 

water annual 

average TOC level, 

before any 

treatment, ≤4.0 

mg/L

TTHM annual average 

≤0.040 mg/L and HAA5 

annual average ≤0.030 

mg/L

One sample per treatment plant 

per quarter at distribution 

system location reflecting 

maximum residence time.

Subpart H system 

serving from 500 to 

9,999 persons 

which has a source 

water annual 

average TOC level, 

before any 

treatment, ≤4.0 

mg/L

TTHM annual average 

≤0.040 mg/L and HAA5 

annual average ≤0.030 

mg/L

One sample per treatment plant 

per year at distribution system 

location reflecting maximum 

residence time during month of 

warmest water temperature. 

NOTE: Any Subpart H system 

serving fewer than 500 persons 

may not reduce its monitoring 

to less than one sample per 

treatment plant per year.

System using only 

ground water not 

under direct 

influence of surface 

TTHM annual average 

≤0.040 mg/L and HAA5 

annual average ≤0.030 

mg/L

One sample per treatment plant 

per year at distribution system 

location reflecting maximum 

residence time during month of 

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(iii) Monitoring requirements for source water TOC. In order to qualify for reduced monitoring for TTHM 

and HAA5 under paragraph (b)(1)(ii) of this section, subpart H systems not monitoring under the 

provisions of paragraph (d) of this section must take monthly TOC samples every 30 days at a location 

prior to any treatment, beginning April 1, 2008 or earlier, if specified by the State. In addition to meeting 

other criteria for reduced monitoring in paragraph (b)(1)(ii) of this section, the source water TOC running 

annual average must be ≤4.0 mg/L (based on the most recent four quarters of monitoring) on a 

continuing basis at each treatment plant to reduce or remain on reduced monitoring for TTHM and 

HAA5. Once qualified for reduced monitoring for TTHM and HAA5 under paragraph (b)(1)(ii) of this 

section, a system may reduce source water TOC monitoring to quarterly TOC samples taken every 90 

days at a location prior to any treatment. 

(iv) Systems on a reduced monitoring schedule may remain on that reduced schedule as long as the 

average of all samples taken in the year (for systems which must monitor quarterly) or the result of the 

sample (for systems which must monitor no more frequently than annually) is no more than 0.060 mg/L 

and 0.045 mg/L for TTHMs and HAA5, respectively. Systems that do not meet these levels must resume 

monitoring at the frequency identified in paragraph (b)(1)(i) of this section (minimum monitoring 

frequency column) in the quarter immediately following the monitoring period in which the system 

exceeds 0.060 mg/L or 0.045 mg/L for TTHMs and HAA5, respectively. For systems using only ground 

water not under the direct influence of surface water and serving fewer than 10,000 persons, if either the 

TTHM annual average is >0.080 mg/L or the HAA5 annual average is >0.060 mg/L, the system must go 

to the increased monitoring identified in paragraph (b)(1)(i) of this section (sample location column) in 

the quarter immediately following the monitoring period in which the system exceeds 0.080 mg/L or 

0.060 mg/L for TTHMs or HAA5 respectively. 

(v) Systems on increased monitoring may return to routine monitoring if, after at least one year of 

monitoring their TTHM annual average is ≤0.060 mg/L and their HAA5 annual average is ≤0.045 mg/L. 

(vi) The State may return a system to routine monitoring at the State's discretion. 

(2) Chlorite. Community and nontransient noncommunity water systems using chlorine dioxide, for 

disinfection or oxidation, must conduct monitoring for chlorite. 

(i) Routine monitoring. (A) Daily monitoring. Systems must take daily samples at the entrance to the 

distribution system. For any daily sample that exceeds the chlorite MCL, the system must take additional 

samples in the distribution system the following day at the locations required by paragraph (b)(2)(ii) of 

this section, in addition to the sample required at the entrance to the distribution system. 

(B) Monthly monitoring. Systems must take a three-sample set each month in the distribution system. 

The system must take one sample at each of the following locations: near the first customer, at a 

location representative of average residence time, and at a location reflecting maximum residence time 

in the distribution system. Any additional routine sampling must be conducted in the same manner (as 

three-sample sets, at the specified locations). The system may use the results of additional monitoring 

conducted under paragraph (b)(2)(ii) of this section to meet the requirement for monitoring in this 

paragraph. 

(ii) Additional monitoring. On each day following a routine sample monitoring result that exceeds the 

chlorite MCL at the entrance to the distribution system, the system is required to take three chlorite 

distribution system samples at the following locations: as close to the first customer as possible, in a 

location representative of average residence time, and as close to the end of the distribution system as 

possible (reflecting maximum residence time in the distribution system). 

(iii) Reduced monitoring. (A) Chlorite monitoring at the entrance to the distribution system required by 

paragraph (b)(2)(i)(A) of this section may not be reduced. 

(B) Chlorite monitoring in the distribution system required by paragraph (b)(2)(i)(B) of this section may 

be reduced to one three-sample set per quarter after one year of monitoring where no individual chlorite 

sample taken in the distribution system under paragraph (b)(2)(i)(B) of this section has exceeded the 

chlorite MCL and the system has not been required to conduct monitoring under paragraph (b)(2)(ii) of 

this section. The system may remain on the reduced monitoring schedule until either any of the three 

individual chlorite samples taken quarterly in the distribution system under paragraph (b)(2)(i)(B) of this 

section exceeds the chlorite MCL or the system is required to conduct monitoring under paragraph (b)(2)

(ii) of this section, at which time the system must revert to routine monitoring. 

(3) Bromate —(i) Routine monitoring. Community and nontransient noncommunity systems using ozone, 

for disinfection or oxidation, must take one sample per month for each treatment plant in the system 

using ozone. Systems must take samples monthly at the entrance to the distribution system while the 

ozonation system is operating under normal conditions. 

(ii) Reduced monitoring. (A) Until March 31, 2009, systems required to analyze for bromate may reduce 

monitoring from monthly to quarterly, if the system's average source water bromide concentration is less 

than 0.05 mg/L based on representative monthly bromide measurements for one year. The system may 

remain on reduced bromate monitoring until the running annual average source water bromide 

concentration, computed quarterly, is equal to or greater than 0.05 mg/L based on representative 

monthly measurements. If the running annual average source water bromide concentration is ≥0.05 

mg/L, the system must resume routine monitoring required by paragraph (b)(3)(i) of this section in the 

following month. 

water using 

chemical 

disinfectant and 

serving at least 

10,000 persons

warmest water temperature

System using only 

ground water not 

under direct 

influence of surface 

water using 

chemical 

disinfectant and 

serving fewer than 

10,000 persons

TTHM annual average 

≤0.040 mg/L and HAA5 

annual average ≤0.030 

mg/L for two 

consecutive years OR 

TTHM annual average 

≤0.020 mg/L and HAA5 

annual average ≤0.015 

mg/L for one year

One sample per treatment plant 

per three year monitoring cycle 

at distribution system location 

reflecting maximum residence 

time during month of warmest 

water temperature, with the 

three-year cycle beginning on 

January 1 following quarter in 

which system qualifies for 

reduced monitoring.

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(B) Beginning April 1, 2009, systems may no longer use the provisions of paragraph (b)(3)(ii)(A) of this 

section to qualify for reduced monitoring. A system required to analyze for bromate may reduce 

monitoring from monthly to quarterly, if the system's running annual average bromate concentration is 

≤0.0025 mg/L based on monthly bromate measurements under paragraph (b)(3)(i) of this section for the 

most recent four quarters, with samples analyzed using Method 317.0 Revision 2.0, 326.0 or 321.8. If a 

system has qualified for reduced bromate monitoring under paragraph (b)(3)(ii)(A) of this section, that 

system may remain on reduced monitoring as long as the running annual average of quarterly bromate 

samples ≤0.0025 mg/L based on samples analyzed using Method 317.0 Revision 2.0, 326.0, or 321.8. If 

the running annual average bromate concentration is >0.0025 mg/L, the system must resume routine 

monitoring required by paragraph (b)(3)(i) of this section. 

(c) Monitoring requirements for disinfectant residuals —(1) Chlorine and chloramines —(i) Routine 

monitoring. Community and nontransient noncommunity water systems that use chlorine or chloramines 

must measure the residual disinfectant level in the distribution system at the same point in the 

distribution system and at the same time as total coliforms are sampled, as specified in §141.21. 

Subpart H systems may use the results of residual disinfectant concentration sampling conducted under 

§141.74(b)(6)(i) for unfiltered systems or §141.74(c)(3)(i) for systems which filter, in lieu of taking 

separate samples. 

(ii) Reduced monitoring. Monitoring may not be reduced. 

(2) Chlorine dioxide —(i) Routine monitoring. Community, nontransient noncommunity, and transient 

noncommunity water systems that use chlorine dioxide for disinfection or oxidation must take daily 

samples at the entrance to the distribution system. For any daily sample that exceeds the MRDL, the 

system must take samples in the distribution system the following day at the locations required by 

paragraph (c)(2)(ii) of this section, in addition to the sample required at the entrance to the distribution 

system. 

(ii) Additional monitoring. On each day following a routine sample monitoring result that exceeds the 

MRDL, the system is required to take three chlorine dioxide distribution system samples. If chlorine 

dioxide or chloramines are used to maintain a disinfectant residual in the distribution system, or if 

chlorine is used to maintain a disinfectant residual in the distribution system and there are no disinfection 

addition points after the entrance to the distribution system ( i.e. , no booster chlorination), the system 

must take three samples as close to the first customer as possible, at intervals of at least six hours. If 

chlorine is used to maintain a disinfectant residual in the distribution system and there are one or more 

disinfection addition points after the entrance to the distribution system ( i.e. , booster chlorination), the 

system must take one sample at each of the following locations: as close to the first customer as 

possible, in a location representative of average residence time, and as close to the end of the 

distribution system as possible (reflecting maximum residence time in the distribution system). 

(iii) Reduced monitoring. Chlorine dioxide monitoring may not be reduced. 

(d) Monitoring requirements for disinfection byproduct precursors (DBPP) —(1) Routine monitoring. 

Subpart H systems which use conventional filtration treatment (as defined in §141.2) must monitor each 

treatment plant for TOC no later than the point of combined filter effluent turbidity monitoring and 

representative of the treated water. All systems required to monitor under this paragraph (d)(1) must 

also monitor for TOC in the source water prior to any treatment at the same time as monitoring for TOC 

in the treated water. These samples (source water and treated water) are referred to as paired samples. 

At the same time as the source water sample is taken, all systems must monitor for alkalinity in the 

source water prior to any treatment. Systems must take one paired sample and one source water 

alkalinity sample per month per plant at a time representative of normal operating conditions and influent 

water quality. 

(2) Reduced monitoring. Subpart H systems with an average treated water TOC of less than 2.0 mg/L 

for two consecutive years, or less than 1.0 mg/L for one year, may reduce monitoring for both TOC and 

alkalinity to one paired sample and one source water alkalinity sample per plant per quarter. The system 

must revert to routine monitoring in the month following the quarter when the annual average treated 

water TOC ≥2.0 mg/L. 

(e) Bromide. Systems required to analyze for bromate may reduce bromate monitoring from monthly to 

once per quarter, if the system demonstrates that the average source water bromide concentration is 

less than 0.05 mg/L based upon representative monthly measurements for one year. The system must 

continue bromide monitoring to remain on reduced bromate monitoring. 

(f) Monitoring plans. Each system required to monitor under this subpart must develop and implement a 

monitoring plan. The system must maintain the plan and make it available for inspection by the State 

and the general public no later than 30 days following the applicable compliance dates in §141.130(b). 

All Subpart H systems serving more than 3300 people must submit a copy of the monitoring plan to the 

State no later than the date of the first report required under §141.134. The State may also require the 

plan to be submitted by any other system. After review, the State may require changes in any plan 

elements. The plan must include at least the following elements. 

(1) Specific locations and schedules for collecting samples for any parameters included in this subpart. 

(2) How the system will calculate compliance with MCLs, MRDLs, and treatment techniques. 

(3) If approved for monitoring as a consecutive system, or if providing water to a consecutive system, 

under the provisions of §141.29, the sampling plan must reflect the entire distribution system. 

[63 FR 69466, Dec. 16, 1998, as amended at 66 FR 3776, Jan. 16, 2001; 69 FR 38856, June 29, 2004; 

71 FR 482, Jan. 4, 2006] 

§ 141.133 Compliance requirements. 

 top

(a) General requirements. (1) Where compliance is based on a running annual average of monthly or 

quarterly samples or averages and the system fails to monitor for TTHM, HAA5, or bromate, this failure 

to monitor will be treated as a monitoring violation for the entire period covered by the annual average. 

Where compliance is based on a running annual average of monthly or quarterly samples or averages 

and the system failure to monitor makes it impossible to determine compliance with MRDLs for chlorine 

and chloramines, this failure to monitor will be treated as a monitoring violation for the entire period 

covered by the annual average. 

(2) All samples taken and analyzed under the provisions of this subpart must be included in determining 

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compliance, even if that number is greater than the minimum required. 

(3) If, during the first year of monitoring under §141.132, any individual quarter's average will cause the 

running annual average of that system to exceed the MCL for total trihalomethanes, haloacetic acids 

(five), or bromate; or the MRDL for chlorine or chloramine, the system is out of compliance at the end of 

that quarter. 

(b) Disinfection byproducts —(1) TTHMs and HAA5. (i) For systems monitoring quarterly, compliance 

with MCLs in §141.64 must be based on a running annual arithmetic average, computed quarterly, of 

quarterly arithmetic averages of all samples collected by the system as prescribed by §141.132(b)(1). 

(ii) For systems monitoring less frequently than quarterly, systems demonstrate MCL compliance if the 

average of samples taken that year under the provisions of §141.132(b)(1) does not exceed the MCLs in 

§141.64. If the average of these samples exceeds the MCL, the system must increase monitoring to 

once per quarter per treatment plant and such a system is not in violation of the MCL until it has 

completed one year of quarterly monitoring, unless the result of fewer than four quarters of monitoring 

will cause the running annual average to exceed the MCL, in which case the system is in violation at the 

end of that quarter. Systems required to increase monitoring frequency to quarterly monitoring must 

calculate compliance by including the sample which triggered the increased monitoring plus the following 

three quarters of monitoring. 

(iii) If the running annual arithmetic average of quarterly averages covering any consecutive four-quarter 

period exceeds the MCL, the system is in violation of the MCL and must notify the public pursuant to 

§141.32 or §141.202, whichever is effective for your system, in addition to reporting to the State 

pursuant to §141.134. 

(iv) If a PWS fails to complete four consecutive quarters of monitoring, compliance with the MCL for the 

last four-quarter compliance period must be based on an average of the available data. 

(2) Bromate. Compliance must be based on a running annual arithmetic average, computed quarterly, of 

monthly samples (or, for months in which the system takes more than one sample, the average f all 

samples taken during the month) collected by the system as prescribed by §141.132(b)(3). If the 

average of samples covering any consecutive four-quarter period exceeds the MCL, the system is in 

violation of the MCL and must notify the public pursuant to subpart Q, in addition to reporting to the State 

pursuant to §141.134. If a PWS fails to complete 12 consecutive months' monitoring, compliance with 

the MCL for the last four-quarter compliance period must be based on an average of the available data. 

(3) Chlorite. Compliance must be based on an arithmetic average of each three sample set taken in the 

distribution system as prescribed by §141.132(b)(2)(i)(B) and §141.132(b)(2)(ii). If the arithmetic average 

of any three sample set exceeds the MCL, the system is in violation of the MCL and must notify the 

public pursuant to subpart Q, in addition to reporting to the State pursuant to §141.134. 

(c) Disinfectant residuals —(1) Chlorine and chloramines. (i) Compliance must be based on a running 

annual arithmetic average, computed quarterly, of monthly averages of all samples collected by the 

system under §141.132(c)(1). If the average covering any consecutive four-quarter period exceeds the 

MRDL, the system is in violation of the MRDL and must notify the public pursuant to subpart Q, in 

addition to reporting to the State pursuant to §141.134. 

(ii) In cases where systems switch between the use of chlorine and chloramines for residual disinfection 

during the year, compliance must be determined by including together all monitoring results of both 

chlorine and chloramines in calculating compliance. Reports submitted pursuant to §141.134 must 

clearly indicate which residual disinfectant was analyzed for each sample. 

(2) Chlorine dioxide. (i) Acute violations. Compliance must be based on consecutive daily samples 

collected by the system under §141.132(c)(2). If any daily sample taken at the entrance to the 

distribution system exceeds the MRDL, and on the following day one (or more) of the three samples 

taken in the distribution system exceed the MRDL, the system is in violation of the MRDL and must take 

immediate corrective action to lower the level of chlorine dioxide below the MRDL and must notify the 

public pursuant to the procedures for acute health risks in subpart Q in addition to reporting to the State 

pursuant to §141.134. Failure to take samples in the distribution system the day following an 

exceedance of the chlorine dioxide MRDL at the entrance to the distribution system will also be 

considered an MRDL violation and the system must notify the public of the violation in accordance with 

the provisions for acute violations under subpart Q in addition to reporting to the State pursuant to 

§141.134. 

(ii) Nonacute violations. Compliance must be based on consecutive daily samples collected by the 

system under §141.132(c)(2). If any two consecutive daily samples taken at the entrance to the 

distribution system exceed the MRDL and all distribution system samples taken are below the MRDL, 

the system is in violation of the MRDL and must take corrective action to lower the level of chlorine 

dioxide below the MRDL at the point of sampling and will notify the public pursuant to the procedures for 

nonacute health risks in subpart Q in addition to reporting to the State pursuant to §141.134. Failure to 

monitor at the entrance to the distribution system the day following an exceedance of the chlorine 

dioxide MRDL at the entrance to the distribution system is also an MRDL violation and the system must 

notify the public of the violation in accordance with the provisions for nonacute violations under §141.32

(e)(78) in addition to reporting to the State pursuant to §141.134. 

(d) Disinfection byproduct precursors (DBPP). Compliance must be determined as specified by 

§141.135(c). Systems may begin monitoring to determine whether Step 1 TOC removals can be met 12 

months prior to the compliance date for the system. This monitoring is not required and failure to monitor 

during this period is not a violation. However, any system that does not monitor during this period, and 

then determines in the first 12 months after the compliance date that it is not able to meet the Step 1 

requirements in §141.135(b)(2) and must therefore apply for alternate minimum TOC removal (Step 2) 

requirements, is not eligible for retroactive approval of alternate minimum TOC removal (Step 2) 

requirements as allowed pursuant to §141.135(b)(3) and is in violation. Systems may apply for alternate 

minimum TOC removal (Step 2) requirements any time after the compliance date. For systems required 

to meet Step 1 TOC removals, if the value calculated under §141.135(c)(1)(iv) is less than 1.00, the 

system is in violation of the treatment technique requirements and must notify the public pursuant to 

subpart Q of this part, in addition to reporting to the State pursuant to §141.134. 

[63 FR 69466, Dec. 16, 1998, as amended at 65 FR 26022, May 4, 2000; 65 FR 40521, June 30, 2000; 

66 FR 3777, Jan. 16, 2001; 69 FR 38856, June 29, 2004; 71 FR 482, Jan. 4, 2006] 

§ 141.134 Reporting and recordkeeping requirements. 

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(a) Systems required to sample quarterly or more frequently must report to the State within 10 days after 

the end of each quarter in which samples were collected, notwithstanding the provisions of §141.31. 

Systems required to sample less frequently than quarterly must report to the State within 10 days after 

the end of each monitoring period in which samples were collected. 

(b) Disinfection byproducts. Systems must report the information specified in the following table: 

1The State may choose to perform calculations and determine whether the MCL was exceeded, in lieu 

of having the system report that information 

(c) Disinfectants. Systems must report the information specified in the following table: 

If you are a * * * You must report * * *

(1) System monitoring for TTHMs and 

HAA5 under the requirements of 

§141.132(b) on a quarterly or more 

frequent basis.

(i) The number of samples taken 

during the last quarter. 

(ii) The location, date, and result of 

each sample taken during the last 

quarter. 

(iii) The arithmetic average of all 

samples taken in the last quarter. 

(iv) The annual arithmetic average of 

the quarterly arithmetic averages of 

this section for the last four quarters. 

(v) Whether, based on §141.133(b)

(1), the MCL was violated.

(2) System monitoring for TTHMs and 

HAA5 under the requirements of 

§141.132(b) less frequently than 

quarterly (but as least annually).

(i) The number of samples taken 

during the last year. 

(ii) The location, date, and result of 

each sample taken during the last 

monitoring period. 

(iii) The arithmetic average of all 

samples taken over the last year. 

(iv) Whether, based on §141.133(b)

(1), the MCL was violated.

(3) System monitoring for TTHMs and 

HAA5 under the requriements of 

§141.132(b) less frequently than 

annually.

(i) The location, date, and result of 

each sample taken 

(ii) Whether, based on §141.133(b)(1), 

the MCL was violated.

(4) System monitoring for chlorite 

under the requirements of §141.132

(b)

(i) The number of entry point samples 

taken each month for the last 3 

months. 

(ii) The location, date, and result of 

each sample (both entry point and 

distribution system) taken during the 

last quarter. 

(iii) For each month in the reporting 

period, the arithmetic average of all 

samples taken in each three samples 

set taken in the distribution system. 

(iv) Whether, based on §141.133(b)

(3), the MCL was violated, in which 

month, and how many times it was 

violated each month.

(5) System monitoring for bromate 

under the requirements of §141.132

(b).

(i)The number of samples taken 

during the last quarter. 

(ii)The location, date, and result of 

each sample taken during the last 

quarter. 

(iii) The arithmetic average of the 

monthly arithmetic averages of all 

samples taken in the last year. 

(iv) Whether, based on §141.133(b)

(2), the MCL was violated.

If you are a * * * You must report * * *

(1) System monitoring for 

chlorine or chloramines under 

the requirements of §141.132(c)

(i) The number of samples taken during 

each month of the last quarter. 

(ii) The month arithmetic average of all 

samples taken in each month for the last 12 

months. 

(iii) The arithmetic average of the monthly 

averages for the last 12 months. 

(iv) Whether, based on §141.133(c)(1), the 

MRD was violated.

(2) System monitoring for 

chlorine dioxide under the 

(i) The dates, result, and locations of 

samples taken during the last quarter. 

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1The State may choose to perform calculations and determine whether the MRDL was exceeded, in lieu 

of having the system report that information. 

(d) Disinfection byproduct precursors and enhanced coagulation or enhanced softening. Systems must 

report the information specified in the following table: 

requirements of §141.132(c). (ii) Whether, based on §141.133(c)(2), the 

MRDL was violated. 

(iii) Whether the MRDL was exceeded in 

any two consecutive daily samples and 

whether the resulting violation was acuate 

or nonacute.

If you are a... You must report...1

(1) System monitoring monthly or 

quarterly for TOC under the 

requirements of §141.132(d) and 

required to meet the enhanced 

coagulation or enhanced softening 

requirements in §141.135(b)(2) or 

(3)

(i) The number of paired (source water 

and treated water) samples taken during 

the last quarter. 

(ii) The location, date, and results of each 

paired sample and associated alkalinity 

taken during the last quarter. 

(iii) For each month in the reporting 

period that paired samples were taken, 

the arithmetic average of the percent 

reduction of TOC for each paired sample 

and the required TOC percent removal. 

(iv) Calculations for determining 

compliance with the TOC percent 

removal requirements, as provided in 

§141.135(c)(1). 

(v) Whether the system is in compliance 

with the enhanced coagulation or 

enhanced softening percent removal 

requirements in §141.135(b) for the last 

four quarters.

(2) System monitoring monthly or 

quarterly for TOC under the 

requirements of §141.132(d) and 

meeting one or more of the 

alternative compliance criteria in 

§141.135(a)(2) or (3)

(i) The alternative compliance criterion 

that the system is using.

 (ii) The number of paired samples taken 

during the last quarter.

 (iii) The location, date, and result of each 

paired sample and associated alkalinity 

taken during the last quarter.

 (iv) The running annual arithmetic 

average based on monthly averages (or 

quarterly samples) of source water TOC 

for systems meeting a criterion in 

§§141.135(a)(2)(i) or (iii) or of treated 

water TOC for systems meeting the 

criterion in §141.135(a)(2)(ii).

 (v) The running annual arithmetic 

average based on monthly averages (or 

quarterly samples) of source water SUVA 

for systems meeting the criterion in 

§141.135(a)(2)(v) or of treated water 

SUVA for systems meeting the criterion in 

§141.135(a)(2)(vi).

 (vi) The running annual average of 

source water alkalinity for systems 

meeting the criterion in §141.135(a)(2)(iii) 

and of treated water alkalinity for systems 

meeting the criterion in §141.135(a)(3)(i).

 (vii) The running annual average for both 

TTHM and HAA5 for systems meeting the 

criterion in §141.135(a)(2)(iii) or (iv).

 (viii) The running annual average of the 

amount of magnesium hardness removal 

(as CaCO3, in mg/L) for systems meeting 

the criterion in §141.135(a)(3)(ii).

 (ix) Whether the system is in compliance 

with the particular alternative compliance 

criterion in §141.135(a)(2) or (3).

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1The State may choose to perform calculations and determine whether the treatment technique was 

met, in lieu of having the system report that information. 

[63 FR 69466, Dec. 16, 1998, as amended at 66 FR 3778, Jan. 16, 2001; 66 FR 9903, Feb. 12, 2001] 

§ 141.135 Treatment technique for control of disinfection byproduct (DBP) precursors. 

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(a) Applicability. (1) Subpart H systems using conventional filtration treatment (as defined in §141.2 ) 

must operate with enhanced coagulation or enhanced softening to achieve the TOC percent removal 

levels specified in paragraph (b) of this section unless the system meets at least one of the alternative 

compliance criteria listed in paragraph (a)(2) or (a)(3) of this section. 

(2) Alternative compliance criteria for enhanced coagulation and enhanced softening systems. Subpart 

H systems using conventional filtration treatment may use the alternative compliance criteria in 

paragraphs (a)(2)(i) through (vi) of this section to comply with this section in lieu of complying with 

paragraph (b) of this section. Systems must still comply with monitoring requirements in §141.132(d). 

(i) The system's source water TOC level, measured according to §141.131(d)(3), is less than 2.0 mg/L, 

calculated quarterly as a running annual average. 

(ii) The system's treated water TOC level, measured according to §141.131(d)(3), is less than 2.0 mg/L, 

calculated quarterly as a running annual average. 

(iii) The system's source water TOC level, measured according to §141.131(d)(3), is less than 4.0 mg/L, 

calculated quarterly as a running annual average; the source water alkalinity, measured according to 

§141.131(d)(1), is greater than 60 mg/L (as CaCO3), calculated quarterly as a running annual average; 

and either the TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 

mg/L, respectively; or prior to the effective date for compliance in §141.130(b), the system has made a 

clear and irrevocable financial commitment not later than the effective date for compliance in §141.130

(b) to use of technologies that will limit the levels of TTHMs and HAA5 to no more than 0.040 mg/L and 

0.030 mg/L, respectively. Systems must submit evidence of a clear and irrevocable financial 

commitment, in addition to a schedule containing milestones and periodic progress reports for 

installation and operation of appropriate technologies, to the State for approval not later than the 

effective date for compliance in §141.130(b). These technologies must be installed and operating not 

later than June 30, 2005. Failure to install and operate these technologies by the date in the approved 

schedule will constitute a violation of National Primary Drinking Water Regulations. 

(iv) The TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, 

respectively, and the system uses only chlorine for primary disinfection and maintenance of a residual in 

the distribution system. 

(v) The system's source water SUVA, prior to any treatment and measured monthly according to 

§141.131(d)(4), is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average. 

(vi) The system's finished water SUVA, measured monthly according to §141.131(d)(4), is less than or 

equal to 2.0 L/mg-m, calculated quarterly as a running annual average. 

(3) Additional alternative compliance criteria for softening systems. Systems practicing enhanced 

softening that cannot achieve the TOC removals required by paragraph (b)(2) of this section may use 

the alternative compliance criteria in paragraphs (a)(3)(i) and (ii) of this section in lieu of complying with 

paragraph (b) of this section. Systems must still comply with monitoring requirements in §141.132(d). 

(i) Softening that results in lowering the treated water alkalinity to less than 60 mg/L (as CaCO3), 

measured monthly according to §141.131(d)(1) and calculated quarterly as a running annual average. 

(ii) Softening that results in removing at least 10 mg/L of magnesium hardness (as CaCO3), measured 

monthly according to §141.131(d)(6) and calculated quarterly as a running annual average. 

(b) Enhanced coagulation and enhanced softening performance requirements. (1) Systems must 

achieve the percent reduction of TOC specified in paragraph (b)(2) of this section between the source 

water and the combined filter effluent, unless the State approves a system's request for alternate 

minimum TOC removal (Step 2) requirements under paragraph (b)(3) of this section. 

(2) Required Step 1 TOC reductions, indicated in the following table, are based upon specified source 

water parameters measured in accordance with §141.131(d). Systems practicing softening are required 

to meet the Step 1 TOC reductions in the far-right column (Source water alkalinity >120 mg/L) for the 

specified source water TOC: 

Step 1 Required Removal of TOC by Enhanced Coagulation and Enhanced Softening for Subpart 

H Systems Using Conventional Treatment1,2

1Systems meeting at least one of the conditions in paragraph (a)(2)(i)–(vi) of this section are not 

required to operate with enhanced coagulation. 

2Softening system meeting one of the alternative compliance criteria in paragraph (a)(3) of this section 

are not required to operate with enhanced softening. 

3System practicing softening must meet the TOC removal requirements in this column.

Source-water 

TOC, mg/L

Source-water alkalinity, mg/L as CaCO3(in precentages)

0–60 >60–120 >1203

>2.0–4.0 35.0 25.0 15.0

>4.0–8.0 45.0 35.0 25.0

>8.0. 50.0 40.0 30.0

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(3) Subpart H conventional treatment systems that cannot achieve the Step 1 TOC removals required by 

paragraph (b)(2) of this section due to water quality parameters or operational constraints must apply to 

the State, within three months of failure to achieve the TOC removals required by paragraph (b)(2) of 

this section, for approval of alternative minimum TOC (Step 2) removal requirements submitted by the 

system. If the State approves the alternative minimum TOC removal (Step 2) requirements, the State 

may make those requirements retroactive for the purposes of determining compliance. Until the State 

approves the alternate minimum TOC removal (Step 2) requirements, the system must meet the Step 1 

TOC removals contained in paragraph (b)(2) of this section. 

(4) Alternate minimum TOC removal (Step 2) requirements. Applications made to the State by enhanced 

coagulation systems for approval of alternate minimum TOC removal (Step 2) requirements under 

paragraph (b)(3) of this section must include, at a minimum, results of bench- or pilot-scale testing 

conducted under paragraph (b)(4)(i) of this section. The submitted bench- or pilot-scale testing must be 

used to determine the alternate enhanced coagulation level. 

(i) Alternate enhanced coagulation level is defined as coagulation at a coagulant dose and pH as 

determined by the method described in paragraphs (b)(4)(i) through (v) of this section such that an 

incremental addition of 10 mg/L of alum (or equivalent amount of ferric salt) results in a TOC removal of 

≤ 0.3 mg/L. The percent removal of TOC at this point on the “TOC removal versus coagulant dose” 

curve is then defined as the minimum TOC removal required for the system. Once approved by the 

State, this minimum requirement supersedes the minimum TOC removal required by the table in 

paragraph (b)(2) of this section. This requirement will be effective until such time as the State approves 

a new value based on the results of a new bench- and pilot-scale test. Failure to achieve State-set 

alternative minimum TOC removal levels is a violation of National Primary Drinking Water Regulations. 

(ii) Bench- or pilot-scale testing of enhanced coagulation must be conducted by using representative 

water samples and adding 10 mg/L increments of alum (or equivalent amounts of ferric salt) until the pH 

is reduced to a level less than or equal to the enhanced coagulation Step 2 target pH shown in the 

following table: 

Enhanced Coagulation Step 2 target pH 

(iii) For waters with alkalinities of less than 60 mg/L for which addition of small amounts of alum or 

equivalent addition of iron coagulant drives the pH below 5.5 before significant TOC removal occurs, the 

system must add necessary chemicals to maintain the pH between 5.3 and 5.7 in samples until the TOC 

removal of 0.3 mg/L per 10 mg/L alum added (or equivalant addition of iron coagulant) is reached. 

(iv) The system may operate at any coagulant dose or pH necessary (consistent with other NPDWRs) to 

achieve the minimum TOC percent removal approved under paragraph (b)(3) of this section. 

(v) If the TOC removal is consistently less than 0.3 mg/L of TOC per 10 mg/L of incremental alum dose 

at all dosages of alum (or equivalant addition of iron coagulant), the water is deemed to contain TOC not 

amenable to enhanced coagulation. The system may then apply to the State for a waiver of enhanced 

coagulation requirements. 

(c) Compliance calculations. (1) Subpart H systems other than those identified in paragraph (a)(2) or (a)

(3) of this section must comply with requirements contained in paragraph (b)(2) or (b)(3) of this section. 

Systems must calculate compliance quarterly, beginning after the system has collected 12 months of 

data, by determining an annual average using the following method: 

(i) Determine actual monthly TOC percent removal, equal to: 

(1−(treated water TOC/source water TOC)) × 100 

(ii) Determine the required monthly TOC percent removal (from either the table in paragraph (b)(2) of 

this section or from paragraph (b)(3) of this section). 

(iii) Divide the value in paragraph (c)(1)(i) of this section by the value in paragraph (c)(1)(ii) of this 

section. 

(iv) Add together the results of paragraph (c)(1)(iii) of this section for the last 12 months and divide by 

12. 

(v) If the value calculated in paragraph (c)(1)(iv) of this section is less than 1.00, the system is not in 

compliance with the TOC percent removal requirements. 

(2) Systems may use the provisions in paragraphs (c)(2)(i) through (v) of this section in lieu of the 

calculations in paragraph (c)(1)(i) through (v) of this section to determine compliance with TOC percent 

removal requirements. 

(i) In any month that the system's treated or source water TOC level, measured according to §141.131

(d)(3), is less than 2.0 mg/L, the system may assign a monthly value of 1.0 (in lieu of the value 

calculated in paragraph (c)(1)(iii) of this section) when calculating compliance under the provisions of 

paragraph (c)(1) of this section. 

(ii) In any month that a system practicing softening removes at least 10 mg/L of magnesium hardness 

(as CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in paragraph 

(c)(1)(iii) of this section) when calculating compliance under the provisions of paragraph (c)(1) of this 

section. 

(iii) In any month that the system's source water SUVA, prior to any treatment and measured according 

to §141.131(d)(4), is ≤2.0 L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value 

calculated in paragraph (c)(1)(iii) of this section) when calculating compliance under the provisions of 

paragraph (c)(1) of this section. 

Alkalinity (mg/L as CaCO3) Target pH

0–60 5.5

>60–120 6.3

>120–240 7.0

>240 7.5

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(iv) In any month that the system's finished water SUVA, measured according to §141.131(d)(4), is ≤2.0 

L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value calculated in paragraph (c)(1)

(iii) of this section) when calculating compliance under the provisions of paragraph (c)(1) of this section. 

(v) In any month that a system practicing enhanced softening lowers alkalinity below 60 mg/L (as 

CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in paragraph (c)

(1)(iii) of this section) when calculating compliance under the provisions of paragraph (c)(1) of this 

section. 

(3) Subpart H systems using conventional treatment may also comply with the requirements of this 

section by meeting the criteria in paragraph (a)(2) or (3) of this section. 

(d) Treatment technique requirements for DBP precursors. The Administrator identifies the following as 

treatment techniques to control the level of disinfection byproduct precursors in drinking water treatment 

and distribution systems: For Subpart H systems using conventional treatment, enhanced coagulation or 

enhanced softening. 

[63 FR 69466, Dec. 16, 1998, as amended at 66 FR 3779, Jan. 16, 2001; 71 FR 482, Jan. 4, 2006] 

Subparts M–N [Reserved] 

 top

Subpart O—Consumer Confidence Reports 

 top

Source: 63 FR 44526, Aug. 19, 1998, unless otherwise noted. 

§ 141.151 Purpose and applicability of this subpart. 

 top

(a) This subpart establishes the minimum requirements for the content of annual reports that community 

water systems must deliver to their customers. These reports must contain information on the quality of 

the water delivered by the systems and characterize the risks (if any) from exposure to contaminants 

detected in the drinking water in an accurate and understandable manner. 

(b) Notwithstanding the provisions of §141.3, this subpart applies only to community water systems. 

(c) For the purpose of this subpart, customers are defined as billing units or service connections to which 

water is delivered by a community water system. 

(d) For the purpose of this subpart, detected means: at or above the levels prescribed by §141.23(a)(4) 

for inorganic contaminants, at or above the levels prescribed by §141.24(f)(7) for the contaminants listed 

in §141.61(a), at or above the levels prescribed by §141.24(h)(18) for the contaminants listed in §141.61

(c), at or above the levels prescribed by §141.131(b)(2)(iv) for the contaminants or contaminant groups 

listed in §141.64, and at or above the levels prescribed by §141.25(c) for radioactive contaminants. 

(e) A State that has primary enforcement responsibility may adopt by rule, after notice and comment, 

alternative requirements for the form and content of the reports. The alternative requirements must 

provide the same type and amount of information as required by §§141.153 and 141.154, and must be 

designed to achieve an equivalent level of public information and education as would be achieved under 

this subpart. 

(f) For purpose of §§141.154 and 141.155 of this subpart, the term “primacy agency” refers to the State 

or tribal government entity that has jurisdiction over, and primary enforcement responsibility for, public 

water systems, even if that government does not have interim or final primary enforcement responsibility 

for this rule. Where the State or tribe does not have primary enforcement responsibility for public water 

systems, the term “primacy agency” refers to the appropriate EPA regional office. 

[63 FR 44526, Aug. 19, 1998, as amended at 71 FR 483, Jan. 4, 2006] 

§ 141.152 Effective dates. 

 top

(a) The regulations in this subpart shall take effect on September 18, 1998. 

(b) Each existing community water system must deliver its first report by October 19, 1999, its second 

report by July 1, 2000, and subsequent reports by July 1 annually thereafter. The first report must 

contain data collected during, or prior to, calendar year 1998 as prescribed in §141.153(d)(3). Each 

report thereafter must contain data collected during, or prior to, the previous calendar year. 

(c) A new community water system must deliver its first report by July 1 of the year after its first full 

calendar year in operation and annually thereafter. 

(d) A community water system that sells water to another community water system must deliver the 

applicable information required in §141.153 to the buyer system: 

(1) No later than April 19, 1999, by April 1, 2000, and by April 1 annually thereafter or 

(2) On a date mutually agreed upon by the seller and the purchaser, and specifically included in a 

contract between the parties. 

§ 141.153 Content of the reports. 

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 top

(a) Each community water system must provide to its customers an annual report that contains the 

information specified in this section and §141.154. 

(b) Information on the source of the water delivered: 

(1) Each report must identify the source(s) of the water delivered by the community water system by 

providing information on: 

(i) The type of the water: e.g., surface water, ground water; and 

(ii) The commonly used name (if any) and location of the body (or bodies) of water. 

(2) If a source water assessment has been completed, the report must notify consumers of the 

availability of this information and the means to obtain it. In addition, systems are encouraged to 

highlight in the report significant sources of contamination in the source water area if they have readily 

available information. Where a system has received a source water assessment from the primacy 

agency, the report must include a brief summary of the system's susceptibility to potential sources of 

contamination, using language provided by the primacy agency or written by the operator. 

(c) Definitions. (1) Each report must include the following definitions: 

(i) Maximum Contaminant Level Goal or MCLG: The level of a contaminant in drinking water below 

which there is no known or expected risk to health. MCLGs allow for a margin of safety. 

(ii) Maximum Contaminant Level or MCL: The highest level of a contaminant that is allowed in drinking 

water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology. 

(2) A report for a community water system operating under a variance or an exemption issued under 

§1415 or 1416 of SDWA must include the following definition: Variances and Exemptions: State or EPA 

permission not to meet an MCL or a treatment technique under certain conditions. 

(3) A report that contains data on contaminants that EPA regulates using any of the following terms must 

include the applicable definitions: 

(i) Treatment Technique: A required process intended to reduce the level of a contaminant in drinking 

water. 

(ii) Action Level: The concentration of a contaminant which, if exceeded, triggers treatment or other 

requirements which a water system must follow. 

(iii) Maximum residual disinfectant level goal or MRDLG: The level of a drinking water disinfectant below 

which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of 

disinfectants to control microbial contaminants. 

(iv) Maximum residual disinfectant level or MRDL: The highest level of a disinfectant allowed in drinking 

water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial 

contaminants. 

(d) Information on detected contaminants. 

(1) This sub-section specifies the requirements for information to be included in each report for 

contaminants subject to mandatory monitoring (except Cryptosporidium ). It applies to: 

(i) Contaminants subject to a MCL, action level, maximum residual disinfectant level, or treatment 

technique (regulated contaminants). 

(ii) Contaminants for which monitoring is required by §141.40 (unregulated contaminants); and 

(iii) Disinfection by-products or microbial contaminants for which monitoring is required by §§141.142 

and 141.143, except as provided under paragraph (e)(1) of this section, and which are detected in the 

finished water. 

(2) The data relating to these contaminants must be displayed in one table or in several adjacent tables. 

Any additional monitoring results which a community water system chooses to include in its report must 

be displayed separately. 

(3) The data must be derived from data collected to comply with EPA and State monitoring and 

analytical requirements during calendar year 1998 for the first report and subsequent calendar years 

thereafter except that: 

(i) Where a system is allowed to monitor for regulated contaminants less often than once a year, the 

table(s) must include the date and results of the most recent sampling and the report must include a 

brief statement indicating that the data presented in the report are from the most recent testing done in 

accordance with the regulations. No data older than 5 years need be included. 

(ii) Results of monitoring in compliance with §§141.142 and 141.143 need only be included for 5 years 

from the date of last sample or until any of the detected contaminants becomes regulated and subject to 

routine monitoring requirements, whichever comes first. 

(4) For detected regulated contaminants (listed in appendix A to this subpart), the table(s) must contain: 

(i) The MCL for that contaminant expressed as a number equal to or greater than 1.0 (as provided in 

appendix A to this subpart); 

(ii) The MCLG for that contaminant expressed in the same units as the MCL; 

(iii) If there is no MCL for a detected contaminant, the table must indicate that there is a treatment 

technique, or specify the action level, applicable to that contaminant, and the report must include the 

definitions for treatment technique and/or action level, as appropriate, specified in paragraph (c)(3) of 

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this section; 

(iv) For contaminants subject to an MCL, except turbidity and total coliforms, the highest contaminant 

level used to determine compliance with an NPDWR and the range of detected levels, as follows: 

(A) When compliance with the MCL is determined annually or less frequently: The highest detected level 

at any sampling point and the range of detected levels expressed in the same units as the MCL. 

(B) When compliance with the MCL is determined by calculating a running annual average of all 

samples taken at a monitoring location: the highest average of any of the monitoring locations and the 

range of all monitoring locations expressed in the same units as the MCL. For the MCLs for TTHM and 

HAA5 in §141.64(b)(2), systems must include the highest locational running annual average for TTHM 

and HAA5 and the range of individual sample results for all monitoring locations expressed in the same 

units as the MCL. If more than one location exceeds the TTHM or HAA5 MCL, the system must include 

the locational running annual averages for all locations that exceed the MCL. 

(C) When compliance with the MCL is determined on a system-wide basis by calculating a running 

annual average of all samples at all monitoring locations: the average and range of detection expressed 

in the same units as the MCL. The system is required to include individual sample results for the IDSE 

conducted under subpart U of this part when determining the range of TTHM and HAA5 results to be 

reported in the annual consumer confidence report for the calendar year that the IDSE samples were 

taken. 

Note to paragraph (d)(4)(iv): When rounding of results to determine compliance with the MCL 

is allowed by the regulations, rounding should be done prior to multiplying the results by the 

factor listed in appendix A of this subpart.

(v) For turbidity. 

(A) When it is reported pursuant to §141.13: The highest average monthly value. 

(B) When it is reported pursuant to the requirements of §141.71: the highest monthly value. The report 

should include an explanation of the reasons for measuring turbidity. 

(C) When it is reported pursuant to §141.73 or §141.173 or §141.551: the highest single measurement 

and the lowest monthly percentage of samples meeting the turbidity limits specified in §141.73 or 

§141.173, or §141.551 for the filtration technology being used. The report should include an explanation 

of the reasons for measuring turbidity; 

(vi) For lead and copper: the 90th percentile value of the most recent round of sampling and the number 

of sampling sites exceeding the action level; 

(vii) For total coliform: 

(A) The highest monthly number of positive samples for systems collecting fewer than 40 samples per 

month; or 

(B) The highest monthly percentage of positive samples for systems collecting at least 40 samples per 

month; 

(viii) For fecal coliform: The total number of positive samples; and 

(ix) The likely source(s) of detected contaminants to the best of the operator's knowledge. Specific 

information regarding contaminants may be available in sanitary surveys and source water 

assessments, and should be used when available to the operator. If the operator lacks specific 

information on the likely source, the report must include one or more of the typical sources for that 

contaminant listed in appendix A to this subpart that is most applicable to the system. 

(5) If a community water system distributes water to its customers from multiple hydraulically 

independent distribution systems that are fed by different raw water sources, the table should contain a 

separate column for each service area and the report should identify each separate distribution system. 

Alternatively, systems could produce separate reports tailored to include data for each service area. 

(6) The table(s) must clearly identify any data indicating violations of MCLs, MRDLs, or treatment 

techniques, and the report must contain a clear and readily understandable explanation of the violation 

including: the length of the violation, the potential adverse health effects, and actions taken by the 

system to address the violation. To describe the potential health effects, the system must use the 

relevant language of appendix A to this subpart. 

(7) For detected unregulated contaminants for which monitoring is required (except Cryptosporidium ), 

the table(s) must contain the average and range at which the contaminant was detected. The report may 

include a brief explanation of the reasons for monitoring for unregulated contaminants. 

(e) Information on Cryptosporidium, radon, and other contaminants: 

(1) If the system has performed any monitoring for Cryptosporidium, including monitoring performed to 

satisfy the requirements of §141.143, which indicates that Cryptosporidium may be present in the source 

water or the finished water, the report must include: 

(i) A summary of the results of the monitoring; and 

(ii) An explanation of the significance of the results. 

(2) If the system has performed any monitoring for radon which indicates that radon may be present in 

the finished water, the report must include: 

(i) The results of the monitoring; and 

(ii) An explanation of the significance of the results. 

(3) If the system has performed additional monitoring which indicates the presence of other 

contaminants in the finished water, EPA strongly encourages systems to report any results which may 

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indicate a health concern. To determine if results may indicate a health concern, EPA recommends that 

systems find out if EPA has proposed an NPDWR or issued a health advisory for that contaminant by 

calling the Safe Drinking Water Hotline (800–426–4791). EPA considers detects above a proposed MCL 

or health advisory level to indicate possible health concerns. For such contaminants, EPA recommends 

that the report include: 

(i) The results of the monitoring; and 

(ii) An explanation of the significance of the results noting the existence of a health advisory or a 

proposed regulation. 

(f) Compliance with NPDWR. In addition to the requirements of §141.153(d)(6), the report must note any 

violation that occurred during the year covered by the report of a requirement listed below, and include a 

clear and readily understandable explanation of the violation, any potential adverse health effects, and 

the steps the system has taken to correct the violation. 

(1) Monitoring and reporting of compliance data; 

(2) Filtration and disinfection prescribed by subpart H of this part. For systems which have failed to 

install adequate filtration or disinfection equipment or processes, or have had a failure of such 

equipment or processes which constitutes a violation, the report must include the following language as 

part of the explanation of potential adverse health effects: Inadequately treated water may contain 

disease-causing organisms. These organisms include bacteria, viruses, and parasites which can cause 

symptoms such as nausea, cramps, diarrhea, and associated headaches. 

(3) Lead and copper control requirements prescribed by subpart I of this part. For systems that fail to 

take one or more actions prescribed by §§141.80(d), 141.81, 141.82, 141.83 or 141.84, the report must 

include the applicable language of appendix A to this subpart for lead, copper, or both. 

(4) Treatment techniques for Acrylamide and Epichlorohydrin prescribed by subpart K of this part. For 

systems that violate the requirements of subpart K of this part, the report must include the relevant 

language from appendix A to this subpart. 

(5) Recordkeeping of compliance data. 

(6) Special monitoring requirements prescribed by §§141.40 and 141.41; and 

(7) Violation of the terms of a variance, an exemption, or an administrative or judicial order. 

(g) Variances and Exemptions. If a system is operating under the terms of a variance or an exemption 

issued under §1415 or 1416 of SDWA, the report must contain: 

(1) An explanation of the reasons for the variance or exemption; 

(2) The date on which the variance or exemption was issued; 

(3) A brief status report on the steps the system is taking to install treatment, find alternative sources of 

water, or otherwise comply with the terms and schedules of the variance or exemption; and 

(4) A notice of any opportunity for public input in the review, or renewal, of the variance or exemption. 

(h) Additional information: 

(1) The report must contain a brief explanation regarding contaminants which may reasonably be 

expected to be found in drinking water including bottled water. This explanation may include the 

language of paragraphs (h)(1) (i) through (iii) or systems may use their own comparable language. The 

report also must include the language of paragraph (h)(1)(iv) of this section. 

(i) The sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, 

reservoirs, springs, and wells. As water travels over the surface of the land or through the ground, it 

dissolves naturally-occurring minerals and, in some cases, radioactive material, and can pick up 

substances resulting from the presence of animals or from human activity. 

(ii) Contaminants that may be present in source water include: 

(A) Microbial contaminants, such as viruses and bacteria, which may come from sewage treatment 

plants, septic systems, agricultural livestock operations, and wildlife. 

(B) Inorganic contaminants, such as salts and metals, which can be naturally-occurring or result from 

urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, 

or farming. 

(C) Pesticides and herbicides, which may come from a variety of sources such as agriculture, urban 

stormwater runoff, and residential uses. 

(D) Organic chemical contaminants, including synthetic and volatile organic chemicals, which are byproducts of industrial processes and petroleum production, and can also come from gas stations, urban 

stormwater runoff, and septic systems. 

(E) Radioactive contaminants, which can be naturally-occurring or be the result of oil and gas production 

and mining activities. 

(iii) In order to ensure that tap water is safe to drink, EPA prescribes regulations which limit the amount 

of certain contaminants in water provided by public water systems. FDA regulations establish limits for 

contaminants in bottled water which must provide the same protection for public health. 

(iv) Drinking water, including bottled water, may reasonably be expected to contain at least small 

amounts of some contaminants. The presence of contaminants does not necessarily indicate that water 

poses a health risk. More information about contaminants and potential health effects can be obtained 

by calling the Environmental Protection Agency's Safe Drinking Water Hotline (800–426–4791). 

(2) The report must include the telephone number of the owner, operator, or designee of the community 

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water system as a source of additional information concerning the report. 

(3) In communities with a large proportion of non-English speaking residents, as determined by the 

Primacy Agency, the report must contain information in the appropriate language(s) regarding the 

importance of the report or contain a telephone number or address where such residents may contact 

the system to obtain a translated copy of the report or assistance in the appropriate language. 

(4) The report must include information (e.g., time and place of regularly scheduled board meetings) 

about opportunities for public participation in decisions that may affect the quality of the water. 

(5) The systems may include such additional information as they deem necessary for public education 

consistent with, and not detracting from, the purpose of the report. 

(6) Systems required to comply with subpart S. (i) Any ground water system that receives notice from 

the State of a significant deficiency or notice from a laboratory of a fecal indicator-positive ground water 

source sample that is not invalidated by the State under §141.402(d) must inform its customers of any 

significant deficiency that is uncorrected at the time of the next report or of any fecal indicator-positive 

ground water source sample in the next report. The system must continue to inform the public annually 

until the State determines that particular significant deficiency is corrected or the fecal contamination in 

the ground water source is addressed under §141.403(a). Each report must include the following 

elements. 

(A) The nature of the particular significant deficiency or the source of the fecal contamination (if the 

source is known) and the date the significant deficiency was identified by the State or the dates of the 

fecal indicator-positive ground water source samples; 

(B) If the fecal contamination in the ground water source has been addressed under §141.403(a) and 

the date of such action; 

(C) For each significant deficiency or fecal contamination in the ground water source that has not been 

addressed under §141.403(a), the State-approved plan and schedule for correction, including interim 

measures, progress to date, and any interim measures completed; and 

(D) If the system receives notice of a fecal indicator-positive ground water source sample that is not 

invalidated by the State under §141.402(d), the potential health effects using the health effects language 

of Appendix A of subpart O. 

(ii) If directed by the State, a system with significant deficiencies that have been corrected before the 

next report is issued must inform its customers of the significant deficiency, how the deficiency was 

corrected, and the date of correction under paragraph (h)(6)(i) of this section. 

[63 FR 44526, Aug. 19, 1998, as amended at 63 FR 69516, Dec. 16, 1998; 64 FR 34733, June 29, 

1999; 65 FR 26022, May 4, 2000; 67 FR 1836, Jan. 14, 2002; 71 FR 483, Jan. 4, 2006; 71 FR 65651, 

Nov. 8, 2006] 

§ 141.154 Required additional health information. 

 top

(a) All reports must prominently display the following language: Some people may be more vulnerable to 

contaminants in drinking water than the general population. Immuno-compromised persons such as 

persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people 

with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk 

from infections. These people should seek advice about drinking water from their health care providers. 

EPA/CDC guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other 

microbial contaminants are available from the Safe Drinking Water Hotline (800–426–4791). 

(b) Ending in the report due by July 1, 2001, a system which detects arsenic at levels above 0.025 mg/L, 

but below the 0.05 mg/L, and beginning in the report due by July 1, 2002, a system that detects arsenic 

above 0.005 mg/L and up to and including 0.010 mg/L: 

(1) Must include in its report a short informational statement about arsenic, using language such as: 

While your drinking water meets EPA's standard for arsenic, it does contain low levels of arsenic. EPA's 

standard balances the current understanding of arsenic's possible health effects against the costs of 

removing arsenic from drinking water. EPA continues to research the health effects of low levels of 

arsenic, which is a mineral known to cause cancer in humans at high concentrations and is linked to 

other health effects such as skin damage and circulatory problems. 

(2) May write its own educational statement, but only in consultation with the Primacy Agency. 

(c) A system which detects nitrate at levels above 5 mg/l, but below the MCL: 

(1) Must include a short informational statement about the impacts of nitrate on children using language 

such as: Nitrate in drinking water at levels above 10 ppm is a health risk for infants of less than six 

months of age. High nitrate levels in drinking water can cause blue baby syndrome. Nitrate levels may 

rise quickly for short periods of time because of rainfall or agricultural activity. If you are caring for an 

infant you should ask advice from your health care provider. 

(2) May write its own educational statement, but only in consultation with the Primacy Agency. 

(d) Every report must include the following lead-specific information: 

(1) A short informational statement about lead in drinking water and its effects on children. The 

statement must include the following information: 

If present, elevated levels of lead can cause serious health problems, especially for pregnant 

women and young children. Lead in drinking water is primarily from materials and 

components associated with service lines and home plumbing. [NAME OF UTILITY] is 

responsible for providing high quality drinking water, but cannot control the variety of materials 

used in plumbing components. When your water has been sitting for several hours, you can 

minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes 

before using water for drinking or cooking. If you are concerned about lead in your water, you 

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may wish to have your water tested. Information on lead in drinking water, testing methods, 

and steps you can take to minimize exposure is available from the Safe Drinking Water 

Hotline or at http://www.epa.gov/safewater/lead. 

(2) A system may write its own educational statement, but only in consultation with the State. 

(e) Community water systems that detect TTHM above 0.080 mg/l, but below the MCL in §141.12, as an 

annual average, monitored and calculated under the provisions of §141.30, must include health effects 

language for TTHMs prescribed by appendix A. 

(f) Beginning in the report due by July 1, 2002, and ending January 22, 2006, a community water system 

that detects arsenic above 0.010 mg/L and up to and including 0.05 mg/L must include the arsenic 

health effects language prescribed by appendix A to subpart O of this part. 

[63 FR 44526, Aug. 19, 1998, as amended at 63 FR 69475, Dec. 16, 1998; 64 FR 34733, June 29, 

1999; 65 FR 26023, May 4, 2000; 66 FR 7064, Jan. 22, 2001; 68 FR 14506, Mar. 25, 2003; 72 FR 

57820, Oct. 10, 2007] 

§ 141.155 Report delivery and recordkeeping. 

 top

(a) Except as provided in paragraph (g) of this section, each community water system must mail or 

otherwise directly deliver one copy of the report to each customer. 

(b) The system must make a good faith effort to reach consumers who do not get water bills, using 

means recommended by the primacy agency. EPA expects that an adequate good faith effort will be 

tailored to the consumers who are served by the system but are not bill-paying customers, such as 

renters or workers. A good faith effort to reach consumers would include a mix of methods appropriate to 

the particular system such as: Posting the reports on the Internet; mailing to postal patrons in 

metropolitan areas; advertising the availability of the report in the news media; publication in a local 

newspaper; posting in public places such as cafeterias or lunch rooms of public buildings; delivery of 

multiple copies for distribution by single-biller customers such as apartment buildings or large private 

employers; delivery to community organizations. 

(c) No later than the date the system is required to distribute the report to its customers, each community 

water system must mail a copy of the report to the primacy agency, followed within 3 months by a 

certification that the report has been distributed to customers, and that the information is correct and 

consistent with the compliance monitoring data previously submitted to the primacy agency. 

(d) No later than the date the system is required to distribute the report to its customers, each 

community water system must deliver the report to any other agency or clearinghouse identified by the 

primacy agency. 

(e) Each community water system must make its reports available to the public upon request. 

(f) Each community water system serving 100,000 or more persons must post its current year's report to 

a publicly-accessible site on the Internet. 

(g) The Governor of a State or his designee, or the Tribal Leader where the tribe has met the eligibility 

requirements contained in §142.72 for the purposes of waiving the mailing requirement, can waive the 

requirement of paragraph (a) of this section for community water systems serving fewer than 10,000 

persons. In consultation with the tribal government, the Regional Administrator may waive the 

requirement of §141.155(a) in areas in Indian country where no tribe has been deemed eligible. 

(1) Such systems must: 

(i) Publish the reports in one or more local newspapers serving the area in which the system is located; 

(ii) Inform the customers that the reports will not be mailed, either in the newspapers in which the reports 

are published or by other means approved by the State; and 

(iii) Make the reports available to the public upon request. 

(2) Systems serving 500 or fewer persons may forego the requirements of paragraphs (g)(1)(i) and (ii) of 

this section if they provide notice at least once per year to their customers by mail, door-to-door delivery 

or by posting in an appropriate location that the report is available upon request. 

(h) Any system subject to this subpart must retain copies of its Consumer Confidence Report for no less 

than 3 years. 

[63 FR 44526, Aug. 19, 1998, as amended at 65 FR 26023, May 4, 2000] 

Appendix A to Subpart O of Part 141—Regulated Contaminants 

 top

Contaminant (units)

Traditional 

MCL in mg/L

To 

convert 

for CCR, 

multiply 

by

MCL in CCR 

units MCLG

Major sources in 

drinking water Health effects language

Microbiological contaminants:

Total Coliform Bacteria MCL: (systems 

that collect ≥40 

samples/month) 

5% of monthly 

samples are 

MCL: (systems 

that collect ≥40 

samples/month) 

5% of monthly 

samples are 

0 Naturally present in 

the environment

Coliforms are bacteria that 

are naturally present in the 

environment and are used 

as an indicator that other, 

potentially-harmful, 

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positive; 

(systems that 

collect <40 

samples/month) 

1 positive 

monthly sample

positive; 

(systems that 

collect <40 

samples/month) 

1 positive 

monthly sample

bacteria may be present. 

Coliforms were found in 

more samples than 

allowed and this was a 

warning of potential 

problems.

Fecal coliform and E. coli 0 0 0 Human and animal 

fecal waste

Fecal coliforms and E. coli 

are bacteria whose 

presence indicates that the 

water may be 

contaminated with human 

or animal wastes. Microbes 

in these wastes can cause 

short-term effects, such as 

diarrhea, cramps, nausea, 

headaches, or other 

symptoms. They may pose 

a special health risk for 

infants, young children, 

some of the elderly, and 

people with severelycompromised immune 

systems.

Fecal Indicators 

(enterococci or coliphage)

TT TT N/A Human and animal 

fecal waste

Fecal indicators are 

microbes whose presence 

indicates that the water 

may be contaminated with 

human or animal wastes. 

Microbes in these wastes 

can cause short-term 

health effects, such as 

diarrhea, cramps, nausea, 

headaches, or other 

symptoms. They may pose 

a special health risk for 

infants, young children, 

some of the elderly, and 

people with severely 

compromised immune 

systems.

Total organic carbon (ppm) TT TT N/A Naturally present in 

the environment

Total organic carbon 

(TOC) has no health 

effects. However, total 

organic carbon provides a 

medium for the formation 

of disinfection by products. 

These byproducts include 

trihalomethanes (THMs) 

and haloacetic acids 

(HAAs). Drinking water 

containing these 

byproducts in excess of the 

MCL may lead to adverse 

health effects, liver or 

kidney problems, or 

nervous system effects, 

and may lead to an 

increased risk of getting 

cancer.

Turbidity (NTU) TT TT N/A Soil runoff Turbidity has no health 

effects. However, turbidity 

can interfere with 

disinfection and provide a 

medium for microbial 

growth. Turbidity may 

indicate the presence of 

disease-causing 

organisms. These 

organisms include 

bacteria, viruses, and 

parasites that can cause 

symptoms such as nausea, 

cramps, diarrhea and 

associated headaches.

Radioactive contaminants:

Beta/photon emitters 4 mrem/yr − 4 0 Decay of natural Certain minerals are 

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(mrem/yr) and man-made 

deposits

radioactive and may emit 

forms of radiation known 

as photons and beta 

radiation. Some people 

who drink water containing 

beta particle and photon 

radioactivity in excess of 

the MCL over many years 

may have an increased 

risk of getting cancer.

Alpha emitters (pCi/L) 15 pCi/L − 15 0 Erosion of natural 

deposits

Certain minerals are 

radioactive and may emit a 

form of radiation known as 

alpha radiation. Some 

people who drink water 

containing alpha emitters 

in excess of the MCL over 

many years may have an 

increased risk of getting 

cancer.

Combined radium (pCi/L) 5 pCi/L − 5 0 Erosion of natural 

deposits

Some people who drink 

water containing radium226 or -228 in excess of 

the MCL over many years 

may have an increased 

risk of getting cancer.

Uranium (pCi/L) 30 μg/L − 30 0 Erosion of natural 

deposits

Some people who drink 

water containing uranium 

in excess of the MCL over 

many years may have an 

increased risk of getting 

cancer and kidney toxicity.

Inorganic contaminants:

Antimony (ppb) .006 1000 6 6 Discharge from 

petroleum 

refineries; fire 

retardants; 

ceramics; 

electronics; solder

Some people who drink 

water containing antimony 

well in excess of the MCL 

over many years could 

experience increases in 

blood cholesterol and 

decreases in blood sugar.

Arsenic (ppb) 10.010 1000 110. 10 Erosion of natural 

deposits; Runoff 

from orchards; 

Runoff from glass 

and electronics 

production wastes

Some people who drink 

water containing arsenic in 

excess of the MCL over 

many years could 

experience skin damage or 

problems with their 

circulatory system, and 

may have an increased 

risk of getting cancer.

Asbestos (MFL) 7 MFL 7 7 Decay of asbestos 

cement water 

mains; Erosion of 

natural deposits

Some people who drink 

water containing asbestos 

in excess of the MCL over 

many years may have an 

increased risk of 

developing benign 

intestinal polyps.

Barium (ppm) 2 2 2 Discharge of drilling 

wastes; Discharge 

from metal 

refineries; Erosion 

of natural deposits

Some people who drink 

water containing barium in 

excess of the MCL over 

many years could 

experience an increase in 

their blood pressure.

Beryllium (ppb) .004 1000 4 4 Discharge from 

metal refineries and 

coal-burning 

factories; 

Discharge from 

electrical, 

aerospace, and 

defense industries

Some people who drink 

water containing beryllium 

well in excess of the MCL 

over many years could 

develop intestinal lesions

Bromate (ppb) .010 1000 10 0 By-product of 

drinkig water 

disinfection

Some people who drink 

water of containing 

bromate in excess of the 

MCL over many years may 

have an increased risk of 

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getting cancer.

Cadmium (ppb) .005 1000 5 5 Corrosion of 

galvanized pipes; 

Erosion of natural 

deposits; Discharge 

from metal 

refineries; Runoff 

from waste 

batteries and paints

Some people who drink 

water containing cadmium 

in excess of the MCL over 

many years could 

experience kidney 

damage.

Chloramines (ppm) MRDL=4 MRDL=4 MRDLG=4 Water additive 

used to control 

microbes

Some people who use 

water containing 

chloramines well in excess 

of the MRDL could 

experience irritating effects 

to their eyes and nose. 

Some people who drink 

water containing 

chloramines well in excess 

of the MRDL could 

experience stomach 

discomfort or anemia.

Chlorine (ppm) MRDL=4 MRDL=4 MRDLG=4 Water additive 

used to control 

microbes

Some people who use 

water containing chlorine 

well in excess of the MRDL 

could experience irritating 

effects to their eyes and 

nose. Some people who 

drink water containing 

chlorine well in excess of 

the MRDL could 

experience stomach 

discomfort.

Chlorine dioxide (ppb) MRDL=.8 1000 MRDL=800 MRDLG=800 Water additive 

used to control 

micorbes

Some infants and young 

children who drink water 

chlorine dioxide in excess 

of the MRDL could 

experience nervous 

system effects. Similar 

effects may occur in 

fetuses of pregnant women 

who drink water containing 

chlorine dioxide in excess 

of the MRDL. Some people 

may experience anemia.

Chlorite (ppm) 1 1 0.8 By-product of 

drinking water 

disinfection

Some infants and young 

children who drink water 

containing chlorite in 

excess of the MCL could 

experience nervous 

system effects. Similar 

effects may occur in 

fetuses of pregnant women 

who drink water containing 

chlorite in excess of the 

MCL. Some people may 

experience anemia.

Chromium (ppb) .1 1000 100 100 Discharge from 

steel and pulp mills; 

Erosion of natural 

deposits

Some people who use 

water containing chromium 

well in excess of the MCL 

over many years could 

experience allergic 

dermatitis.

Copper (ppm) AL=1.3 AL=1.3 1.3 Corrosion of 

household 

plumbing systems; 

Erosion of natural 

deposits

Copper is an essential 

nutrient, but some people 

who drink water containing 

copper in excess of the 

action level over a 

relatively short amount of 

time could experience 

gastrointestinal distress. 

Some people who drink 

water containing copper in 

excess of the action level 

over many years could 

suffer liver or kidney 

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damage. People with 

Wilson's disease should 

consult their personal 

doctor.

Cyanide (ppb) .2 1000 200 200 Discharge from 

steel/metal 

factories; 

Discharge from 

plastic and fertilizer 

factories

Some people who drink 

water containing cyanide 

well in excess of the MCL 

over many years could 

experience nerve damage 

or problems with their 

thyroid.

Fluoride (ppm) 4 4 4 Erosion of natural 

deposits; Water 

additive which 

promotes strong 

teeth; Discharge 

from fertilizer and 

aluminum factories

Some people who drink 

water containing fluoride in 

excess of the MCL over 

many years could get bone 

disease, including pain and 

tenderness of the bones. 

Fluoride in drinking water 

at half the MCL or more 

may cause mottling of 

children's teeth, usually in 

children less than nine 

years old. Mottling, also 

known as dental fluorosis, 

may include brown staining 

and/or pitting of the teeth, 

and occurs only in 

developing teeth before 

they erupt from the gums.

Lead (ppb) AL=.015 1000 AL=15 0 Corrosion of 

household 

plumbing systems; 

Erosion of natural 

deposits

Infants and children who 

drink water containing lead 

in excess of the action 

level could experience 

delays in their physical or 

mental development. 

Children could show slight 

deficits in attention span 

and learning abilities. 

Adults who drink this water 

over many years could 

develop kidney problems 

or high blood pressure.

Mercury [inorganic] (ppb) .002 1000 2 2 Erosion of natural 

deposits; Dis 

charge from 

refineries and 

factories; Runoff 

from landfills; 

Runoff from 

cropland

Some people who drink 

water containing inorganic 

mercury well in excess of 

the MCL over many years 

could experience kidney 

damage.

Nitrate (ppm) 10 10 10 Runoff from 

fertilizer use; 

Leaching from 

septic tanks, sew 

age; Erosion of 

natural deposits

Infants below the age of six 

months who drink water 

containing nitrate in excess 

of the MCL could become 

seriously ill and, if 

untreated, may die. 

Symptoms include 

shortness of breath and 

blue baby syndrome.

Nitrite (ppm) 1 1 1 Runoff from 

fertilizer use; 

Leaching from 

septic tanks, sew 

age; Erosion of 

natural deposits

Infants below the age of six 

months who drink water 

containing nitrite in excess 

of the MCL could become 

seriously ill and, if 

untreated, may die. 

Symptoms include 

shortness of breath and 

blue baby syndrome.

Selenium (ppb) .05 1000 50 50 Discharge from 

petroleum and 

metal refineries; 

Erosion of natural 

deposits; Discharge 

from mines

Selenium is an essential 

nutrient. However, some 

people who drink water 

containing selenium in 

excess of the MCL over 

many years could 

experience hair or 

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fingernail losses, 

numbness in fingers or 

toes, or problems with their 

circulation.

Thallium (ppb) .002 1000 2 0.5 Leaching from oreprocessing sites; 

Discharge from 

electronics, glass, 

and drug factories

Some people who drink 

water containing thallium in 

excess of the MCL over 

many years could 

experience hair loss, 

changes in their blood, or 

problems with their 

kidneys, intestines, or liver.

Synthetic organic contaminants 

including pesticides and herbicides:

2,4-D (ppb) .07 1000 70 70 Runoff from 

herbicide used on 

row crops

Some people who drink 

water containing the weed 

killer 2,4-D well in excess 

of the MCL over many 

years could experience 

problems with their 

kidneys, liver, or adrenal 

glands.

2,4,5-TP [Silvex](ppb) .05 1000 50 50 Residue of banned 

herbicide

Some people who drink 

water containing silvex in 

excess of the MCL over 

many years could 

experience liver problems.

Acrylamide TT TT 0 Added to water 

during 

sewage/wastewater 

treatment

Some people who drink 

water containing high 

levels of acrylamide over a 

long period of time could 

have problems with their 

nervous system or blood, 

and may have an 

increased risk of getting 

cancer.

Alachlor (ppb) .002 1000 2 0 Runoff from 

herbicide used on 

row crops

Some people who drink 

water containing alachlor in 

excess of the MCL over 

many years could have 

problems with their eyes, 

liver, kidneys, or spleen, or 

experience anemia, and 

may have an increased 

risk of getting cancer.

Atrazine (ppb) .003 1000 3 3 Runoff from 

herbicide used on 

row crops

Some people who drink 

water containing atrazine 

well in excess of the MCL 

over many years could 

experience problems with 

their cardiovascular system 

or reproductive difficulties.

Benzo(a)pyrene [PAH] 

(nanograms/l)

.0002 1,000,000 200 0 Leaching from 

linings of water 

storage tanks and 

distribution lines

Some people who drink 

water containing benzo(a)

pyrene in excess of the 

MCL over many years may 

experience reproductive 

difficulties and may have 

an increased risk of getting 

cancer.

Carbofuran (ppb) .04 1000 40 40 Leaching of soil 

fumigant used on 

rice and alfalfa

Some people who drink 

water containing 

carbofuran in excess of the 

MCL over many years 

could experience problems 

with their blood, or nervous 

or reproductive systems.

Chlordane (ppb) .002 1000 2 0 Residue of banned 

termiticide

Some people who drink 

water containing chlordane 

in excess of the MCL over 

many years could 

experience problems with 

their liver or nervous 

system, and may have an 

increased risk of getting 

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cancer.

Dalapon (ppb) .2 1000 200 200 Runoff from 

herbicide used on 

rights of way

Some people who drink 

water containing dalapon 

well in excess of the MCL 

over many years could 

experience minor kidney 

changes.

Di(2-ethylhexyl) adipate 

(ppb)

.4 1000 400 400 Discharge from 

chemical factories

Some people who drink 

water containing di(2-

ethylhexyl) adipate well in 

excess of the MCL over 

many years could 

experience toxic effects 

such as weight loss, liver 

enlargement or possible 

reproductive difficulties.

Di(2-ethylhexyl) phthalate 

(ppb)

.006 1000 6 0 Discharge from 

rubber and 

chemical factories

Some people who drink 

water containing di(2-

ethylhexyl) phthalate well 

in excess of the MCL over 

many years may have 

problems with their liver, or 

experience reproductive 

difficulties, and may have 

an increased risk of getting 

cancer.

Dibromochloropropane 

(ppt)

.0002 1,000,000 200 0 Runoff/leaching 

from soil fumigant 

used on soybeans, 

cotton, pineapples, 

and orchards

Some people who drink 

water containing DBCP in 

excess of the MCL over 

many years could 

experience reproductive 

problems and may have an 

increased risk of getting 

cancer.

Dinoseb (ppb) .007 1000 7 7 Runoff from 

herbicide used on 

soybeans and 

vegetables

Some people who drink 

water containing dinoseb 

well in excess of the MCL 

over many years could 

experience reproductive 

difficulties.

Diquat (ppb) .02 1000 20 20 Runoff from 

herbicide use

Some people who drink 

water containing diquat in 

excess of the MCL over 

many years could get 

cataracts.

Dioxin [2,3,7,8-TCDD] 

(ppq)

.00000003 1,000,000, 

000

30 0 Emissions from 

waste incineration 

and other 

combustion; 

Discharge from 

chemical factories

Some people who drink 

water containing dioxin in 

excess of the MCL over 

many years could 

experience reproductive 

difficulties and may have 

an increased risk of getting 

cancer.

Endothall (ppb) .1 1000 100 100 Runoff from 

herbicide use

Some people who drink 

water containing endothall 

in excess of the MCL over 

many years could 

experience problems with 

their stomach or intestines.

Endrin (ppb) .002 1000 2 2 Residue of banned 

insecticide

Some people who drink 

water containing endrin in 

excess of the MCL over 

many years could 

experience liver problems.

Epichlorohydrin TT TT 0 Discharge from 

industrial chemical 

factories; An 

impurity of some 

water treatment 

chemicals

Some people who drink 

water containing high 

levels of epichlorohydrin 

over a long period of time 

could experience stomach 

problems, and may have 

an increased risk of getting 

cancer.

Ethylene dibromide (ppt) .00005 1,000,000 50 0 Discharge from 

petroleum 

Some people who drink 

water containing ethylene 

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refineries dibromide in excess of the 

MCL over many years 

could experience problems 

with their liver, stomach, 

reproductive system, or 

kidneys, and may have an 

increased risk of getting 

cancer.

Glyphosate (ppb) .7 1000 700 700 Runoff from 

herbicide use

Some people who drink 

water containing 

glyphosate in excess of the 

MCL over many years 

could experience problems 

with their kidneys or 

reproductive difficulties.

Heptachlor (ppt) .0004 1,000,000 400 0 Residue of banned 

pesticide

Some people who drink 

water containing 

heptachlor in excess of the 

MCL over many years 

could experience liver 

damage and may have an 

increased risk of getting 

cancer.

Heptachlor epoxide (ppt) .0002 1,000,000 200 0 Breakdown of 

heptachlor

Some people who drink 

water containing 

heptachlor epoxide in 

excess of the MCL over 

many years could 

experience liver damage, 

and may have an 

increased risk of getting 

cancer.

Hexachlorobenzene (ppb) .001 1000 1 0 Discharge from 

metal refineries and 

agricultural 

chemical factories

Some people who drink 

water containing 

hexachlorobenzene in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys, or 

adverse reproductive 

effects, and may have an 

increased risk of getting 

cancer.

Hexachlorocyclopentadiene 

(ppb)

.05 1000 50 50 Discharge from 

chemical factories

Some people who drink 

water containing 

hexachlorocyclopentadiene 

well in excess of the MCL 

over many years could 

experience problems with 

their kidneys or stomach.

Lindane (ppt) .0002 1,000,000 200 200 Runoff/leaching 

from insecticide 

used on cattle, 

lumber, gardens

Some people who drink 

water containing lindane in 

excess of the MCL over 

many years could 

experience problems with 

their kidneys or liver.

Methoxychlor (ppb) .04 1000 40 40 Runoff/leaching 

from insecticide 

used on fruits, 

vegetables, alfalfa, 

livestock

Some people who drink 

water containing 

methoxychlor in excess of 

the MCL over many years 

could experience 

reproductive difficulties.

Oxamyl [Vydate] (ppb) .2 1000 200 200 Runoff/leaching 

from insecticide 

used on apples, 

potatoes and 

tomatoes

Some people who drink 

water containing oxamyl in 

excess of the MCL over 

many years could 

experience slight nervous 

system effects.

PCBs [Polychlorinated 

biphenyls] (ppt)

.0005 1,000,000 500 0 Runoff from 

landfills; Discharge 

of waste chemicals

Some people who drink 

water containing PCBs in 

excess of the MCL over 

many years could 

experience changes in 

their skin, problems with 

their thymus gland, 

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immune deficiencies, or 

reproductive or nervous 

system difficulties, and 

may have an increased 

risk of getting cancer.

Pentachlorophenol (ppb) .001 1000 1 0 Discharge from 

wood preserving 

factories

Some people who drink 

water containing 

pentachlorophenol in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys, and 

may have an increased 

risk of getting cancer.

Picloram (ppb) .5 1000 500 500 Herbicide runoff Some people who drink 

water containing picloram 

in excess of the MCL over 

many years could 

experience problems with 

their liver.

Simazine (ppb) .004 1000 4 4 Herbicide runoff Some people who drink 

water containing simazine 

in excess of the MCL over 

many years could 

experience problems with 

their blood.

Toxaphene (ppb) .003 1000 3 0 Runoff/leaching 

from insecticide 

used on cotton and 

cattle

Some people who drink 

water containing 

toxaphene in excess of the 

MCL over many years 

could have problems with 

their kidneys, liver, or 

thyroid, and may have an 

increased risk of getting 

cancer.

Volatile organic contaminants:

Benzene (ppb) .005 1000 5 0 Discharge from 

factories; Leaching 

from gas storage 

tanks and landfills

Some people who drink 

water containing benzene 

in excess of the MCL over 

many years could 

experience anemia or a 

decrease in blood 

platelets, and may have an 

increased risk of getting 

cancer.

Carbon tetrachloride (ppb) .005 1000 5 0 Discharge from 

chemical plants 

and other industrial 

activities

Some people who drink 

water containing carbon 

tetrachloride in excess of 

the MCL over many years 

could experience problems 

with their liver and may 

have an increased risk of 

getting cancer.

Chlorobenzene (ppb) .1 1000 100 100 Discharge from 

chemical and 

agricultural 

chemical factories

Some people who drink 

water containing 

chlorobenzene in excess of 

the MCL over many years 

could experience problems 

with their liver or kidneys.

o-Dichlorobenzene (ppb) .6 1000 600 600 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing odichlorobenzene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver, kidneys, or 

circulatory systems.

p-Dichlorobenzene (ppb) .075 1000 75 75 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing pdichlorobenzene in excess 

of the MCL over many 

years could experience 

anemia, damage to their 

liver, kidneys, or spleen, or 

changes in their blood.

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1,2-Dichloroethane (ppb) .005 1000 5 0 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing 1,2-

dichloroethane in excess of 

the MCL over many years 

may have an increased 

risk of getting cancer.

1,1-Dichloroethylene (ppb) .007 1000 7 7 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing 1,1-

dichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver.

cis-1,2-Dichloroethylene 

(ppb)

.07 1000 70 70 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing cis-1,2-

dichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver.

trans-1,2-Dichloroethylene 

(ppb)

.1 1000 100 100 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing trans-1,2-

dichloroethylene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver.

Dichloromethane (ppb) .005 1000 5 0 Discharge from 

pharmaceutical and 

chemical factories

Some people who drink 

water containing 

dichloromethane in excess 

of the MCL over many 

years could have liver 

problems and may have an 

increased risk of getting 

cancer.

1,2-Dichloropropane (ppb) .005 1000 5 0 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing 1,2-

dichloropropane in excess 

of the MCL over many 

years may have an 

increased risk of getting 

cancer.

Ethylbenzene (ppb) .7 1000 700 700 Discharge from 

petroleum 

refineries

Some people who drink 

water containing 

ethylbenzene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys.

Haloacetic Acids (HAA) 

(ppb)

.060 1000 60 N/A By-product of 

drinking water 

disinfection

Some people who drink 

water containing haloacetic 

acids in excess of the MCL 

over many years may have 

an increased risk of getting 

cancer.

Styrene (ppb) .1 1000 100 100 Discharge from 

rubber and plastic 

factories; Leaching 

from landfills

Some people who drink 

water containing styrene 

well in excess of the MCL 

over many years could 

have problems with their 

liver, kidneys, or circulatory 

system.

Tetrachloroethylene (ppb) .005 1000 5 0 Discharge from 

factories and dry 

cleaners

Some people who drink 

water containing 

tetrachloroethylene in 

excess of the MCL over 

many years could have 

problems with their liver, 

and may have an 

increased risk of getting 

cancer.

1,2,4-Trichlorobenzene 

(ppb)

.07 1000 70 70 Discharge from 

textile-finishing 

factories

Some people who drink 

water containing 1,2,4-

trichlorobenzene well in 

excess of the MCL over 

many years could 

experience changes in 

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1These arsenic values are effective January 23, 2006. Until then, the MCL is 0.05 mg/L and there is no 

MCLG. 

Key: 

AL=Action Level 

MCL=Maximum Contaminant Level 

MCLG=Maximum Contaminant Level Goal 

MFL=million fibers per liter 

MRDL=Maximum Residual Disinfectant Level 

MRDLG=Maximum Residual Disinfectant Level Goal 

mrem/year=millirems per year (a measure of radiation absorbed by the body) 

N/A=Not Applicable 

their adrenal glands.

1,1,1-Trichloroethane (ppb) .2 1000 200 200 Discharge from 

metal degreasing 

sites and other 

factories

Some people who drink 

water containing 1,1,1-

trichloroethane in excess 

of the MCL over many 

years could experience 

problems with their liver, 

nervous system, or 

circulatory system.

1,1,2-Trichloroethane (ppb) .005 1000 5 3 Discharge from 

industrial chemical 

factories

Some people who drink 

water containing 1,1,2-

trichloroethane well in 

excess of the MCL over 

many years could have 

problems with their liver, 

kidneys, or immune 

systems.

Trichloroethylene (ppb) .005 1000 5 0 Discharge from 

metal degreasing 

sites and other 

factories

Some people who drink 

water containing 

trichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver 

and may have an 

increased risk of getting 

cancer.

TTHMs [Total 

trihalomethanes] (ppb)

0.10/.080 1000 100/80 N/A By-product of 

drinking water 

disinfection

Some people who drink 

water containing 

trihalomethanes in excess 

of the MCL over many 

years may experience 

problems with their liver, 

kidneys, or central nervous 

systems, and may have an 

increased risk of getting 

cancer.

Toluene (ppm) 1 1 1 Discharge from 

petroleum factories

Some people who drink 

water containing toluene 

well in excess of the MCL 

over many years could 

have problems with their 

nervous system, kidneys, 

or liver.

Vinyl Chloride (ppb) .002 1000 2 0 Leaching from PVC 

piping; Discharge 

from plastics 

factories

Some people who drink 

water containing vinyl 

chloride in excess of the 

MCL over many years may 

have an increased risk of 

getting cancer.

Xylenes (ppm) 10 10 10 Discharge from 

petroleum factories; 

Discharge from 

chemical factories

Some people who drink 

water containing xylenes in 

excess of the MCL over 

many years could 

experience damage to their 

nervous system.

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NTU=Nephelometric Turbidity Units (a measure of water clarity) 

pCi/l=picocuries per liter (a measure of radioactivity) 

ppm=parts per million, or milligrams per liter (mg/l) 

ppb=parts per billion, or micrograms per liter (μg/l) 

ppt=parts per trillion, or nanograms per liter 

ppq=parts per quadrillion, or picograms per liter 

TT=Treatment Technique 

[65 FR 26024, May 4, 2000, as amended at 65 FR 76749, Dec. 7, 2000; 66 FR 7064, Jan. 22, 2001; 67 

FR 70855, Nov. 27, 2002; 67 FR 73011, Dec. 9, 2002; 68 FR 14506, Mar. 25, 2003; 71 FR 65652, Nov. 

8, 2006] 

Subpart P—Enhanced Filtration and Disinfection—Systems Serving 10,000 or More 

People 

 top

Source: 63 FR 69516, Dec. 16, 1998, unless otherwise noted. 

§ 141.170 General requirements. 

 top

(a) The requirements of this subpart P constitute national primary drinking water regulations. These 

regulations establish requirements for filtration and disinfection that are in addition to criteria under which 

filtration and disinfection are required under subpart H of this part. The requirements of this subpart are 

applicable to subpart H systems serving at least 10,000 people, beginning January 1, 2002 unless 

otherwise specified in this subpart. The regulations in this subpart establish or extend treatment 

technique requirements in lieu of maximum contaminant levels for the following contaminants: Giardia 

lamblia, viruses, heterotrophic plate count bacteria, Legionella, Cryptosporidium, and turbidity. Each 

subpart H system serving at least 10,000 people must provide treatment of its source water that 

complies with these treatment technique requirements and are in addition to those identified in §141.70. 

The treatment technique requirements consist of installing and properly operating water treatment 

processes which reliably achieve: 

(1) At least 99 percent (2-log) removal of Cryptosporidium between a point where the raw water is not 

subject to recontamination by surface water runoff and a point downstream before or at the first 

customer for filtered systems, or Cryptosporidium control under the watershed control plan for unfiltered 

systems. 

(2) Compliance with the profiling and benchmark requirements under the provisions of §141.172. 

(b) A public water system subject to the requirements of this subpart is considered to be in compliance 

with the requirements of paragraph (a) of this section if: 

(1) It meets the requirements for avoiding filtration in §§141.71 and 141.171 and the disinfection 

requirements in §§141.72 and 141.172; or 

(2) It meets the applicable filtration requirements in either §141.73 or §141.173 and the disinfection 

requirements in §§141.72 and 141.172. 

(c) Systems are not permitted to begin construction of uncovered finished water storage facilities 

beginning February 16, 1999. 

(d) Subpart H systems that did not conduct optional monitoring under §141.172 because they served 

fewer than 10,000 persons when such monitoring was required, but serve more than 10,000 persons 

prior to January 1, 2005 must comply with §§141.170, 141.171, 141.173, 141.174, and 141.175. These 

systems must also consult with the State to establish a disinfection benchmark. A system that decides to 

make a significant change to its disinfection practice, as described in §141.172(c)(1)(i) through (iv) must 

consult with the State prior to making such change. 

[63 FR 69516, Dec. 16, 1998, as amended at 66 FR 3779, Jan. 16, 2001; 67 FR 1836, Jan. 14, 2002; 69 

FR 38856, June 29, 2004] 

§ 141.171 Criteria for avoiding filtration. 

 top

In addition to the requirements of §141.71, a public water system subject to the requirements of this 

subpart that does not provide filtration must meet all of the conditions of paragraphs (a) and (b) of this 

section. 

(a) Site-specific conditions. In addition to site-specific conditions in §141.71(b), systems must maintain 

the watershed control program under §141.71(b)(2) to minimize the potential for contamination by 

Cryptosporidium oocysts in the source water. The watershed control program must, for 

Cryptosporidium : 

(1) Identify watershed characteristics and activities which may have an adverse effect on source water 

quality; and 

(2) Monitor the occurrence of activities which may have an adverse effect on source water quality. 

(b) During the onsite inspection conducted under the provisions of §141.71(b)(3), the State must 

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determine whether the watershed control program established under §141.71(b)(2) is adequate to limit 

potential contamination by Cryptosporidium oocysts. The adequacy of the program must be based on 

the comprehensiveness of the watershed review; the effectiveness of the system's program to monitor 

and control detrimental activities occurring in the watershed; and the extent to which the water system 

has maximized land ownership and/or controlled land use within the watershed. 

§ 141.172 Disinfection profiling and benchmarking. 

 top

(a) Determination of systems required to profile. A public water system subject to the requirements of 

this subpart must determine its TTHM annual average using the procedure in paragraph (a)(1) of this 

section and its HAA5 annual average using the procedure in paragraph (a)(2) of this section. The annual 

average is the arithmetic average of the quarterly averages of four consecutive quarters of monitoring. 

(1) The TTHM annual average must be the annual average during the same period as is used for the 

HAA5 annual average. 

(i) Those systems that collected data under the provisions of subpart M (Information Collection Rule) 

must use the results of the samples collected during the last four quarters of required monitoring under 

§141.142. 

(ii) Those systems that use “grandfathered” HAA5 occurrence data that meet the provisions of 

paragraph (a)(2)(ii) of this section must use TTHM data collected at the same time under the provisions 

of §§141.12 and 141.30. 

(iii) Those systems that use HAA5 occurrence data that meet the provisions of paragraph (a)(2)(iii)(A) of 

this section must use TTHM data collected at the same time under the provisions of §§141.12 and 

141.30. 

(2) The HAA5 annual average must be the annual average during the same period as is used for the 

TTHM annual average. 

(i) Those systems that collected data under the provisions of subpart M (Information Collection Rule) 

must use the results of the samples collected during the last four quarters of required monitoring under 

§141.142. 

(ii) Those systems that have collected four quarters of HAA5 occurrence data that meets the routine 

monitoring sample number and location requirements for TTHM in §§141.12 and 141.30 and handling 

and analytical method requirements of §141.142(b)(1) may use those data to determine whether the 

requirements of this section apply. 

(iii) Those systems that have not collected four quarters of HAA5 occurrence data that meets the 

provisions of either paragraph (a)(2)(i) or (ii) of this section by March 16, 1999 must either: 

(A) Conduct monitoring for HAA5 that meets the routine monitoring sample number and location 

requirements for TTHM in §§141.12 and 141.30 and handling and analytical method requirements of 

§141.142(b)(1) to determine the HAA5 annual average and whether the requirements of paragraph (b) 

of this section apply. This monitoring must be completed so that the applicability determination can be 

made no later than March 31, 2000, or 

(B) Comply with all other provisions of this section as if the HAA5 monitoring had been conducted and 

the results required compliance with paragraph (b) of this section. 

(3) The system may request that the State approve a more representative annual data set than the data 

set determined under paragraph (a)(1) or (2) of this section for the purpose of determining applicability of 

the requirements of this section. 

(4) The State may require that a system use a more representative annual data set than the data set 

determined under paragraph (a)(1) or (2) of this section for the purpose of determining applicability of 

the requirements of this section. 

(5) The system must submit data to the State on the schedule in paragraphs (a)(5)(i) through (v) of this 

section. 

(i) Those systems that collected TTHM and HAA5 data under the provisions of subpart M (Information 

Collection Rule), as required by paragraphs (a)(1)(i) and (a)(2)(i) of this section, must submit the results 

of the samples collected during the last 12 months of required monitoring under §141.142 not later than 

December 31, 1999. 

(ii) Those systems that have collected four consecutive quarters of HAA5 occurrence data that meets 

the routine monitoring sample number and location for TTHM in §§141.12 and 141.30 and handling and 

analytical method requirements of §141.142(b)(1), as allowed by paragraphs (a)(1)(ii) and (a)(2)(ii) of 

this section, must submit those data to the State not later than April 16, 1999. Until the State has 

approved the data, the system must conduct monitoring for HAA5 using the monitoring requirements 

specified under paragraph (a)(2)(iii) of this section. 

(iii) Those systems that conduct monitoring for HAA5 using the monitoring requirements specified by 

paragraphs (a)(1)(iii) and (a)(2)(iii)(A) of this section, must submit TTHM and HAA5 data not later than 

March 31, 2000. 

(iv) Those systems that elect to comply with all other provisions of this section as if the HAA5 monitoring 

had been conducted and the results required compliance with this section, as allowed under paragraphs 

(a)(2)(iii)(B) of this section, must notify the State in writing of their election not later than December 31, 

1999. 

(v) If the system elects to request that the State approve a more representative annual data set than the 

data set determined under paragraph (a)(2)(i) of this section, the system must submit this request in 

writing not later than December 31, 1999. 

(6) Any system having either a TTHM annual average ≥0.064 mg/L or an HAA5 annual average ≥0.048 

mg/L during the period identified in paragraphs (a)(1) and (2) of this section must comply with paragraph 

(b) of this section. 

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(b) Disinfection profiling. (1) Any system that meets the criteria in paragraph (a)(6) of this section must 

develop a disinfection profile of its disinfection practice for a period of up to three years. 

(2) The system must monitor daily for a period of 12 consecutive calendar months to determine the total 

logs of inactivation for each day of operation, based on the CT99.9 values in Tables 1.1–1.6, 2.1, and 

3.1 of §141.74(b), as appropriate, through the entire treatment plant. This system must begin this 

monitoring not later than April 1, 2000. As a minimum, the system with a single point of disinfectant 

application prior to entrance to the distribution system must conduct the monitoring in paragraphs (b)(2)

(i) through (iv) of this section. A system with more than one point of disinfectant application must conduct 

the monitoring in paragraphs (b)(2)(i) through (iv) of this section for each disinfection segment. The 

system must monitor the parameters necessary to determine the total inactivation ratio, using analytical 

methods in §141.74(a), as follows: 

(i) The temperature of the disinfected water must be measured once per day at each residual 

disinfectant concentration sampling point during peak hourly flow. 

(ii) If the system uses chlorine, the pH of the disinfected water must be measured once per day at each 

chlorine residual disinfectant concentration sampling point during peak hourly flow. 

(iii) The disinfectant contact time(s) (“T”) must be determined for each day during peak hourly flow. 

(iv) The residual disinfectant concentration(s) (“C”) of the water before or at the first customer and prior 

to each additional point of disinfection must be measured each day during peak hourly flow. 

(3) In lieu of the monitoring conducted under the provisions of paragraph (b)(2) of this section to develop 

the disinfection profile, the system may elect to meet the requirements of paragraph (b)(3)(i) of this 

section. In addition to the monitoring conducted under the provisions of paragraph (b)(2) of this section 

to develop the disinfection profile, the system may elect to meet the requirements of paragraph (b)(3)(ii) 

of this section. 

(i) A PWS that has three years of existing operational data may submit those data, a profile generated 

using those data, and a request that the State approve use of those data in lieu of monitoring under the 

provisions of paragraph (b)(2) of this section not later than March 31, 2000. The State must determine 

whether these operational data are substantially equivalent to data collected under the provisions of 

paragraph (b)(2) of this section. These data must also be representative of Giardia lamblia inactivation 

through the entire treatment plant and not just of certain treatment segments. Until the State approves 

this request, the system is required to conduct monitoring under the provisions of paragraph (b)(2) of this 

section. 

(ii) In addition to the disinfection profile generated under paragraph (b)(2) of this section, a PWS that has 

existing operational data may use those data to develop a disinfection profile for additional years. Such 

systems may use these additional yearly disinfection profiles to develop a benchmark under the 

provisions of paragraph (c) of this section. The State must determine whether these operational data are 

substantially equivalent to data collected under the provisions of paragraph (b)(2) of this section. These 

data must also be representative of inactivation through the entire treatment plant and not just of certain 

treatment segments. 

(4) The system must calculate the total inactivation ratio as follows: 

(i) If the system uses only one point of disinfectant application, the system may determine the total 

inactivation ratio for the disinfection segment based on either of the methods in paragraph (b)(4)(i)(A) or 

(b)(4)(i)(B) of this section. 

(A) Determine one inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly 

flow. 

(B) Determine successive CTcalc/CT99.9values, representing sequential inactivation ratios, between the 

point of disinfectant application and a point before or at the first customer during peak hourly flow. Under 

this alternative, the system must calculate the total inactivation ratio by determining (CTcalc/CT99.9) for 

each sequence and then adding the (CTcalc/CT99.9) values together to determine (Σ (CTcalc/CT99.9)). 

(ii) If the system uses more than one point of disinfectant application before the first customer, the 

system must determine the CT value of each disinfection segment immediately prior to the next point of 

disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. 

The (CTcalc/CT99.9) value of each segment and (Σ(CTcalc/CT99.9)) must be calculated using the 

method in paragraph (b)(4)(i) of this section. 

(iii) The system must determine the total logs of inactivation by multiplying the value calculated in 

paragraph (b)(4)(i) or (ii) of this section by 3.0. 

(5) A system that uses either chloramines or ozone for primary disinfection must also calculate the logs 

of inactivation for viruses using a method approved by the State. 

(6) The system must retain disinfection profile data in graphic form, as a spreadsheet, or in some other 

format acceptable to the State for review as part of sanitary surveys conducted by the State. 

(c) Disinfection benchmarking. (1) Any system required to develop a disinfection profile under the 

provisions of paragraphs (a) and (b) of this section and that decides to make a significant change to its 

disinfection practice must consult with the State prior to making such change. Significant changes to 

disinfection practice are: 

(i) Changes to the point of disinfection; 

(ii) Changes to the disinfectant(s) used in the treatment plant; 

(iii) Changes to the disinfection process; and 

(iv) Any other modification identified by the State. 

(2) Any system that is modifying its disinfection practice must calculate its disinfection benchmark using 

the procedure specified in paragraphs (c)(2)(i) through (ii) of this section. 

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(i) For each year of profiling data collected and calculated under paragraph (b) of this section, the 

system must determine the lowest average monthly Giardia lamblia inactivation in each year of profiling 

data. The system must determine the average Giardia lamblia inactivation for each calendar month for 

each year of profiling data by dividing the sum of daily Giardia lamblia of inactivation by the number of 

values calculated for that month. 

(ii) The disinfection benchmark is the lowest monthly average value (for systems with one year of 

profiling data) or average of lowest monthly average values (for systems with more than one year of 

profiling data) of the monthly logs of Giardia lamblia inactivation in each year of profiling data. 

(3) A system that uses either chloramines or ozone for primary disinfection must also calculate the 

disinfection benchmark for viruses using a method approved by the State. 

(4) The system must submit information in paragraphs (c)(4)(i) through (iii) of this section to the State as 

part of its consultation process. 

(i) A description of the proposed change; 

(ii) The disinfection profile for Giardia lamblia (and, if necessary, viruses) under paragraph (b) of this 

section and benchmark as required by paragraph (c)(2) of this section; and 

(iii) An analysis of how the proposed change will affect the current levels of disinfection. 

[63 FR 69516, Dec. 16, 1998, as amended at 66 FR 3779, Jan. 16, 2001] 

§ 141.173 Filtration. 

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A public water system subject to the requirements of this subpart that does not meet all of the criteria in 

this subpart and subpart H of this part for avoiding filtration must provide treatment consisting of both 

disinfection, as specified in §141.72(b), and filtration treatment which complies with the requirements of 

paragraph (a) or (b) of this section or §141.73 (b) or (c) by December 31, 2001. 

(a) Conventional filtration treatment or direct filtration. (1) For systems using conventional filtration or 

direct filtration, the turbidity level of representative samples of a system's filtered water must be less than 

or equal to 0.3 NTU in at least 95 percent of the measurements taken each month, measured as 

specified in §141.74(a) and (c). 

(2) The turbidity level of representative samples of a system's filtered water must at no time exceed 1 

NTU, measured as specified in §141.74(a) and (c). 

(3) A system that uses lime softening may acidify representative samples prior to analysis using a 

protocol approved by the State. 

(b) Filtration technologies other than conventional filtration treatment, direct filtration, slow sand filtration, 

or diatomaceous earth filtration. A public water system may use a filtration technology not listed in 

paragraph (a) of this section or in §141.73(b) or (c) if it demonstrates to the State, using pilot plant 

studies or other means, that the alternative filtration technology, in combination with disinfection 

treatment that meets the requirements of §141.72(b), consistently achieves 99.9 percent removal and/or 

inactivation of Giardia lamblia cysts and 99.99 percent removal and/or inactivation of viruses, and 99 

percent removal of Cryptosporidium oocysts, and the State approves the use of the filtration technology. 

For each approval, the State will set turbidity performance requirements that the system must meet at 

least 95 percent of the time and that the system may not exceed at any time at a level that consistently 

achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts, 99.99 percent removal and/or 

inactivation of viruses, and 99 percent removal of Cryptosporidium oocysts. 

[63 FR 69516, Dec. 16, 1998, as amended at 65 FR 20313, Apr. 14, 2000; 66 FR 3779, Jan. 16, 2001] 

§ 141.174 Filtration sampling requirements. 

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(a) Monitoring requirements for systems using filtration treatment. In addition to monitoring required by 

§141.74, a public water system subject to the requirements of this subpart that provides conventional 

filtration treatment or direct filtration must conduct continuous monitoring of turbidity for each individual 

filter using an approved method in §141.74(a) and must calibrate turbidimeters using the procedure 

specified by the manufacturer. Systems must record the results of individual filter monitoring every 15 

minutes. 

(b) If there is a failure in the continuous turbidity monitoring equipment, the system must conduct grab 

sampling every four hours in lieu of continuous monitoring, but for no more than five working days 

following the failure of the equipment. 

§ 141.175 Reporting and recordkeeping requirements. 

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In addition to the reporting and recordkeeping requirements in §141.75, a public water system subject to 

the requirements of this subpart that provides conventional filtration treatment or direct filtration must 

report monthly to the State the information specified in paragraphs (a) and (b) of this section beginning 

January 1, 2002. In addition to the reporting and recordkeeping requirements in §141.75, a public water 

system subject to the requirements of this subpart that provides filtration approved under §141.173(b) 

must report monthly to the State the information specified in paragraph (a) of this section beginning 

January 1, 2002. The reporting in paragraph (a) of this section is in lieu of the reporting specified in 

§141.75(b)(1). 

(a) Turbidity measurements as required by §141.173 must be reported within 10 days after the end of 

each month the system serves water to the public. Information that must be reported includes: 

(1) The total number of filtered water turbidity measurements taken during the month. 

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(2) The number and percentage of filtered water turbidity measurements taken during the month which 

are less than or equal to the turbidity limits specified in §141.173(a) or (b). 

(3) The date and value of any turbidity measurements taken during the month which exceed 1 NTU for 

systems using conventional filtration treatment or direct filtration, or which exceed the maximum level set 

by the State under §141.173(b). 

(b) Systems must maintain the results of individual filter monitoring taken under §141.174 for at least 

three years. Systems must report that they have conducted individual filter turbidity monitoring under 

§141.174 within 10 days after the end of each month the system serves water to the public. Systems 

must report individual filter turbidity measurement results taken under §141.174 within 10 days after the 

end of each month the system serves water to the public only if measurements demonstrate one or 

more of the conditions in paragraphs (b)(1) through (4) of this section. Systems that use lime softening 

may apply to the State for alternative exceedance levels for the levels specified in paragraphs (b)(1) 

through (4) of this section if they can demonstrate that higher turbidity levels in individual filters are due 

to lime carryover only and not due to degraded filter performance. 

(1) For any individual filter that has a measured turbidity level of greater than 1.0 NTU in two consecutive 

measurements taken 15 minutes apart, the system must report the filter number, the turbidity 

measurement, and the date(s) on which the exceedance occurred. In addition, the system must either 

produce a filter profile for the filter within 7 days of the exceedance (if the system is not able to identify 

an obvious reason for the abnormal filter performance) and report that the profile has been produced or 

report the obvious reason for the exceedance. 

(2) For any individual filter that has a measured turbidity level of greater than 0.5 NTU in two consecutive 

measurements taken 15 minutes apart at the end of the first four hours of continuous filter operation 

after the filter has been backwashed or otherwise taken offline, the system must report the filter number, 

the turbidity, and the date(s) on which the exceedance occurred. In addition, the system must either 

produce a filter profile for the filter within 7 days of the exceedance (if the system is not able to identify 

an obvious reason for the abnormal filter performance) and report that the profile has been produced or 

report the obvious reason for the exceedance. 

(3) For any individual filter that has a measured turbidity level of greater than 1.0 NTU in two consecutive 

measurements taken 15 minutes apart at any time in each of three consecutive months, the system 

must report the filter number, the turbidity measurement, and the date(s) on which the exceedance 

occurred. In addition, the system must conduct a self-assessment of the filter within 14 days of the 

exceedance and report that the self-assessment was conducted. The self assessment must consist of at 

least the following components: assessment of filter performance; development of a filter profile; 

identification and prioritization of factors limiting filter performance; assessment of the applicability of 

corrections; and preparation of a filter self-assessment report. 

(4) For any individual filter that has a measured turbidity level of greater than 2.0 NTU in two consecutive 

measurements taken 15 minutes apart at any time in each of two consecutive months, the system must 

report the filter number, the turbidity measurement, and the date(s) on which the exceedance occurred. 

In addition, the system must arrange for the conduct of a comprehensive performance evaluation by the 

State or a third party approved by the State no later than 30 days following the exceedance and have 

the evaluation completed and submitted to the State no later than 90 days following the exceedance. 

(c) Additional reporting requirements. (1) If at any time the turbidity exceeds 1 NTU in representative 

samples of filtered water in a system using conventional filtration treatment or direct filtration, the system 

must inform the State as soon as possible, but no later than the end of the next business day. 

(2) If at any time the turbidity in representative samples of filtered water exceeds the maximum level set 

by the State under §141.173(b) for filtration technologies other than conventional filtration treatment, 

direct filtration, slow sand filtration, or diatomaceous earth filtration, the system must inform the State as 

soon as possible, but no later than the end of the next business day. 

[63 FR 69516, Dec. 16, 1998, as amended at 66 FR 3779, Jan. 16, 2001] 

Subpart Q—Public Notification of Drinking Water Violations 

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Source: 65 FR 26035, May 4, 2000, unless otherwise noted. 

§ 141.201 General public notification requirements. 

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Public water systems in States with primacy for the public water system supervision (PWSS) program 

must comply with the requirements in this subpart no later than May 6, 2002 or on the date the Stateadopted rule becomes effective, whichever comes first. Public water systems in jurisdictions where EPA 

directly implements the PWSS program must comply with the requirements in this subpart on October 

31, 2000. Prior to these dates, public water systems must continue to comply with the public notice 

requirements in §141.32 of this part. The term “primacy agency” is used in this subpart to refer to either 

EPA or the State or the Tribe in cases where EPA, the State, or the Tribe exercises primary enforcement 

responsibility for this subpart. 

(a) Who must give public notice? Each owner or operator of a public water system (community water 

systems, non-transient non-community water systems, and transient non-community water systems) 

must give notice for all violations of national primary drinking water regulations (NPDWR) and for other 

situations, as listed in Table 1. The term “NPDWR violations” is used in this subpart to include violations 

of the maximum contaminant level (MCL), maximum residual disinfection level (MRDL), treatment 

technique (TT), monitoring requirements, and testing procedures in this part 141. Appendix A to this 

subpart identifies the tier assignment for each specific violation or situation requiring a public notice. 

Table 1 to §141.201—Violation Categories and Other Situations Requiring a Public Notice 

(1) NPDWR violations:

(i) Failure to comply with an applicable maximum contaminant level 

(MCL) or maximum residual disinfectant level (MRDL).

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(b) What type of public notice is required for each violation or situation? Public notice requirements are 

divided into three tiers, to take into account the seriousness of the violation or situation and of any 

potential adverse health effects that may be involved. The public notice requirements for each violation 

or situation listed in Table 1 of this section are determined by the tier to which it is assigned. Table 2 of 

this section provides the definition of each tier. Appendix A of this part identifies the tier assignment for 

each specific violation or situation. 

Table 2 to §141.201—Definition of Public Notice Tiers 

(c) Who must be notified? (1) Each public water system must provide public notice to persons served by 

the water system, in accordance with this subpart. Public water systems that sell or otherwise provide 

drinking water to other public water systems ( i.e. , to consecutive systems) are required to give public 

notice to the owner or operator of the consecutive system; the consecutive system is responsible for 

providing public notice to the persons it serves. 

(2) If a public water system has a violation in a portion of the distribution system that is physically or 

hydraulically isolated from other parts of the distribution system, the primacy agency may allow the 

system to limit distribution of the public notice to only persons served by that portion of the system which 

is out of compliance. Permission by the primacy agency for limiting distribution of the notice must be 

granted in writing. 

(3) A copy of the notice must also be sent to the primacy agency, in accordance with the requirements 

under §141.31(d). 

§ 141.202 Tier 1 Public Notice —Form, manner, and frequency of notice. 

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(a) Which violations or situations require a Tier 1 public notice? Table 1 of this section lists the violation 

categories and other situations requiring a Tier 1 public notice. Appendix A to this subpart identifies the 

tier assignment for each specific violation or situation. 

Table 1 to §141.202—Violation Categories and Other Situations Requiring a Tier 1 Public Notice 

(ii) Failure to comply with a prescribed treatment technique (TT).

(iii) Failure to perform water quality monitoring, as required by the 

drinking water regulations.

(iv) Failure to comply with testing procedures as prescribed by a drinking 

water regulation.

(2) Variance and exemptions under sections 1415 and 1416 of SDWA:

(i) Operation under a variance or an exemption.

(ii) Failure to comply with the requirements of any schedule that has 

been set under a variance or exemption.

(3) Special public notices:

(i) Occurrence of a waterborne disease outbreak or other waterborne 

emergency.

(ii) Exceedance of the nitrate MCL by non-community water systems 

(NCWS), where granted permission by the primacy agency under 141.11

(d) of this part.

(iii) Exceedance of the secondary maximum contaminant level (SMCL) 

for fluoride.

(iv) Availability of unregulated contaminant monitoring data.

(v) Other violations and situations determined by the primacy agency to 

require a public notice under this subpart, not already listed in Appendix 

A.

(1) Tier 1 public notice —required for NPDWR violations and situations with 

significant potential to have serious adverse effects on human health as a 

result of short-term exposure.

(2) Tier 2 public notice —required for all other NPDWR violations and 

situations with potential to have serious adverse effects on human health.

(3) Tier 3 public notice —required for all other NPDWR violations and 

situations not included in Tier 1 and Tier 2.

(1) Violation of the MCL for total coliforms when fecal coliform or E. coli are 

present in the water distribution system (as specified in §141.63(b)), or when 

the water system fails to test for fecal coliforms or E. coli when any repeat 

sample tests positive for coliform (as specified in §141.21(e));

(2) Violation of the MCL for nitrate, nitrite, or total nitrate and nitrite, as 

defined in §141.62, or when the water system fails to take a confirmation 

sample within 24 hours of the system's receipt of the first sample showing an 

exceedance of the nitrate or nitrite MCL, as specified in §141.23(f)(2);

(3) Exceedance of the nitrate MCL by non-community water systems, where 

permitted to exceed the MCL by the primacy agency under §141.11(d), as 

required under §141.209;

(4) Violation of the MRDL for chlorine dioxide, as defined in §141.65(a), when 

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(b) When is the Tier 1 public notice to be provided? What additional steps are required? Public water 

systems must: 

(1) Provide a public notice as soon as practical but no later than 24 hours after the system learns of the 

violation; 

(2) Initiate consultation with the primacy agency as soon as practical, but no later than 24 hours after the 

public water system learns of the violation or situation, to determine additional public notice 

requirements; and 

(3) Comply with any additional public notification requirements (including any repeat notices or direction 

on the duration of the posted notices) that are established as a result of the consultation with the 

primacy agency. Such requirements may include the timing, form, manner, frequency, and content of 

repeat notices (if any) and other actions designed to reach all persons served. 

(c) What is the form and manner of the public notice? Public water systems must provide the notice 

within 24 hours in a form and manner reasonably calculated to reach all persons served. The form and 

manner used by the public water system are to fit the specific situation, but must be designed to reach 

residential, transient, and non-transient users of the water system. In order to reach all persons served, 

water systems are to use, at a minimum, one or more of the following forms of delivery: 

(1) Appropriate broadcast media (such as radio and television); 

(2) Posting of the notice in conspicuous locations throughout the area served by the water system; 

(3) Hand delivery of the notice to persons served by the water system; or 

(4) Another delivery method approved in writing by the primacy agency. 

[65 FR 26035, May 4, 2000, as amended at 67 FR 1836, Jan. 14, 2002; 71 FR 65652, Nov. 8, 2006] 

§ 141.203 Tier 2 Public Notice —Form, manner, and frequency of notice. 

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(a) Which violations or situations require a Tier 2 public notice? Table 1 of this section lists the violation 

categories and other situations requiring a Tier 2 public notice. Appendix A to this subpart identifies the 

tier assignment for each specific violation or situation. 

Table 1 to §141.203—Violation Categories and Other Situations Requiring a Tier 2 Public Notice 

one or more samples taken in the distribution system the day following an 

exceedance of the MRDL at the entrance of the distribution system exceed 

the MRDL, or when the water system does not take the required samples in 

the distribution system, as specified in §141.133(c)(2)(i);

(5) Violation of the turbidity MCL under §141.13(b), where the primacy 

agency determines after consultation that a Tier 1 notice is required or where 

consultation does not take place within 24 hours after the system learns of 

the violation;

(6) Violation of the Surface Water Treatment Rule (SWTR), Interim Enhanced 

Surface Water Treatment Rule (IESWTR) or Long Term 1 Enhanced Surface 

Water Treatment Rule (LT1ESWTR) treatment technique requirement 

resulting from a single exceedance of the maximum allowable turbidity limit 

(as identified in appendix A), where the primacy agency determines after 

consultation that a Tier 1 notice is required or where consultation does not 

take place within 24 hours after the system learns of the violation;

(7) Occurrence of a waterborne disease outbreak, as defined in §141.2, or 

other waterborne emergency (such as a failure or significant interruption in 

key water treatment processes, a natural disaster that disrupts the water 

supply or distribution system, or a chemical spill or unexpected loading of 

possible pathogens into the source water that significantly increases the 

potential for drinking water contamination);

(8) Detection of E. coli , enterococci, or coliphage in source water samples as 

specified in §141.402(a) and §141.402(b);

(9) Other violations or situations with significant potential to have serious 

adverse effects on human health as a result of short-term exposure, as 

determined by the primacy agency either in its regulations or on a case-bycase basis.

(1) All violations of the MCL, MRDL, and treatment technique requirements, 

except where a Tier 1 notice is required under §141.202(a) or where the 

primacy agency determines that a Tier 1 notice is required;

(2) Violations of the monitoring and testing procedure requirements, where 

the primacy agency determines that a Tier 2 rather than a Tier 3 public notice 

is required, taking into account potential health impacts and persistence of 

the violation; and

(3) Failure to comply with the terms and conditions of any variance or 

exemption in place.

(4) Failure to take corrective action or failure to maintain at least 4-log 

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(b) When is the Tier 2 public notice to be provided? (1) Public water systems must provide the public 

notice as soon as practical, but no later than 30 days after the system learns of the violation. If the public 

notice is posted, the notice must remain in place for as long as the violation or situation persists, but in 

no case for less than seven days, even if the violation or situation is resolved. The primacy agency may, 

in appropriate circumstances, allow additional time for the initial notice of up to three months from the 

date the system learns of the violation. It is not appropriate for the primacy agency to grant an extension 

to the 30-day deadline for any unresolved violation or to allow across-the-board extensions by rule or 

policy for other violations or situations requiring a Tier 2 public notice. Extensions granted by the primacy 

agency must be in writing. 

(2) The public water system must repeat the notice every three months as long as the violation or 

situation persists, unless the primacy agency determines that appropriate circumstances warrant a 

different repeat notice frequency. In no circumstance may the repeat notice be given less frequently than 

once per year. It is not appropriate for the primacy agency to allow less frequent repeat notice for an 

MCL violation under the Total Coliform Rule or a treatment technique violation under the Surface Water 

Treatment Rule or Interim Enhanced Surface Water Treatment Rule. It is also not appropriate for the 

primacy agency to allow through its rules or policies across-the-board reductions in the repeat notice 

frequency for other ongoing violations requiring a Tier 2 repeat notice. Primacy agency determinations 

allowing repeat notices to be given less frequently than once every three months must be in writing. 

(3) For the turbidity violations specified in this paragraph, public water systems must consult with the 

primacy agency as soon as practical but no later than 24 hours after the public water system learns of 

the violation, to determine whether a Tier 1 public notice under §141.202(a) is required to protect public 

health. When consultation does not take place within the 24-hour period, the water system must 

distribute a Tier 1 notice of the violation within the next 24 hours ( i.e., no later than 48 hours after the 

system learns of the violation), following the requirements under §141.202(b) and (c). Consultation with 

the primacy agency is required for: 

(i) Violation of the turbidity MCL under §141.13(b); or 

(ii) Violation of the SWTR, IESWTR or LT1ESWTR treatment technique requirement resulting from a 

single exceedance of the maximum allowable turbidity limit. 

(c) What is the form and manner of the Tier 2 public notice? Public water systems must provide the initial 

public notice and any repeat notices in a form and manner that is reasonably calculated to reach 

persons served in the required time period. The form and manner of the public notice may vary based on 

the specific situation and type of water system, but it must at a minimum meet the following 

requirements: 

(1) Unless directed otherwise by the primacy agency in writing, community water systems must provide 

notice by: 

(i) Mail or other direct delivery to each customer receiving a bill and to other service connections to 

which water is delivered by the public water system; and 

(ii) Any other method reasonably calculated to reach other persons regularly served by the system, if 

they would not normally be reached by the notice required in paragraph (c)(1)(i) of this section. Such 

persons may include those who do not pay water bills or do not have service connection addresses 

(e.g., house renters, apartment dwellers, university students, nursing home patients, prison inmates, 

etc.). Other methods may include: Publication in a local newspaper; delivery of multiple copies for 

distribution by customers that provide their drinking water to others (e.g., apartment building owners or 

large private employers); posting in public places served by the system or on the Internet; or delivery to 

community organizations. 

(2) Unless directed otherwise by the primacy agency in writing, non-community water systems must 

provide notice by: 

(i) Posting the notice in conspicuous locations throughout the distribution system frequented by persons 

served by the system, or by mail or direct delivery to each customer and service connection (where 

known); and 

(ii) Any other method reasonably calculated to reach other persons served by the system if they would 

not normally be reached by the notice required in paragraph (c)(2)(i) of this section. Such persons may 

include those served who may not see a posted notice because the posted notice is not in a location 

they routinely pass by. Other methods may include: Publication in a local newspaper or newsletter 

distributed to customers; use of E-mail to notify employees or students; or, delivery of multiple copies in 

central locations (e.g., community centers). 

[65 FR 26035, May 4, 2000, as amended at 67 FR 1836, Jan. 14, 2002; 71 FR 65652, Nov. 8, 2006] 

§ 141.204 Tier 3 Public Notice —Form, manner, and frequency of notice. 

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(a) Which violations or situations require a Tier 3 public notice? Table 1 of this section lists the violation 

categories and other situations requiring a Tier 3 public notice. Appendix A to this subpart identifies the 

tier assignment for each specific violation or situation. 

Table 1 to §141.204—Violation Categories and Other Situations Requiring a Tier 3 Public Notice 

treatment of viruses (using inactivation, removal, or a State-approved 

combination of 4-log virus inactivation and removal) before or at the first 

customer under §141.403(a).

(1) Monitoring violations under 40 CFR part 141, except where a Tier 1 notice 

is required under §141.202(a) or where the primacy agency determines that a 

Tier 2 notice is required;

(2) Failure to comply with a testing procedure established in 40 CFR part 

141, except where a Tier 1 notice is required under §141.202(a)) or where 

the primacy agency determines that a Tier 2 notice is required;

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(b) When is the Tier 3 public notice to be provided? (1) Public water systems must provide the public 

notice not later than one year after the public water system learns of the violation or situation or begins 

operating under a variance or exemption. Following the initial notice, the public water system must 

repeat the notice annually for as long as the violation, variance, exemption, or other situation persists. If 

the public notice is posted, the notice must remain in place for as long as the violation, variance, 

exemption, or other situation persists, but in no case less than seven days (even if the violation or 

situation is resolved). 

(2) Instead of individual Tier 3 public notices, a public water system may use an annual report detailing 

all violations and situations that occurred during the previous twelve months, as long as the timing 

requirements of paragraph (b)(1) of this section are met. 

(c) What is the form and manner of the Tier 3 public notice? Public water systems must provide the initial 

notice and any repeat notices in a form and manner that is reasonably calculated to reach persons 

served in the required time period. The form and manner of the public notice may vary based on the 

specific situation and type of water system, but it must at a minimum meet the following requirements: 

(1) Unless directed otherwise by the primacy agency in writing, community water systems must provide 

notice by: 

(i) Mail or other direct delivery to each customer receiving a bill and to other service connections to 

which water is delivered by the public water system; and 

(ii) Any other method reasonably calculated to reach other persons regularly served by the system, if 

they would not normally be reached by the notice required in paragraph (c)(1)(i) of this section. Such 

persons may include those who do not pay water bills or do not have service connection addresses 

(e.g., house renters, apartment dwellers, university students, nursing home patients, prison inmates, 

etc.). Other methods may include: Publication in a local newspaper; delivery of multiple copies for 

distribution by customers that provide their drinking water to others (e.g., apartment building owners or 

large private employers); posting in public places or on the Internet; or delivery to community 

organizations. 

(2) Unless directed otherwise by the primacy agency in writing, non-community water systems must 

provide notice by: 

(i) Posting the notice in conspicuous locations throughout the distribution system frequented by persons 

served by the system, or by mail or direct delivery to each customer and service connection (where 

known); and 

(ii) Any other method reasonably calculated to reach other persons served by the system, if they would 

not normally be reached by the notice required in paragraph (c)(2)(i) of this section. Such persons may 

include those who may not see a posted notice because the notice is not in a location they routinely 

pass by. Other methods may include: Publication in a local newspaper or newsletter distributed to 

customers; use of E-mail to notify employees or students; or, delivery of multiple copies in central 

locations (e.g., community centers). 

(d) In what situations may the Consumer Confidence Report be used to meet the Tier 3 public notice 

requirements? For community water systems, the Consumer Confidence Report (CCR) required under 

Subpart O of this part may be used as a vehicle for the initial Tier 3 public notice and all required repeat 

notices, as long as: 

(1) The CCR is provided to persons served no later than 12 months after the system learns of the 

violation or situation as required under §141.204(b); 

(2) The Tier 3 notice contained in the CCR follows the content requirements under §141.205; and 

(3) The CCR is distributed following the delivery requirements under §141.204(c). 

[65 FR 26035, May 4, 2000; 65 FR 38629, June 21, 2000] 

§ 141.205 Content of the public notice. 

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(a) What elements must be included in the public notice for violations of National Primary Drinking Water 

Regulations (NPDWR) or other situations requiring a public notice? When a public water system violates 

a NPDWR or has a situation requiring public notification, each public notice must include the following 

elements: 

(1) A description of the violation or situation, including the contaminant(s) of concern, and (as applicable) 

the contaminant level(s); 

(2) When the violation or situation occurred; 

(3) Any potential adverse health effects from the violation or situation, including the standard language 

under paragraph (d)(1) or (d)(2) of this section, whichever is applicable; 

(4) The population at risk, including subpopulations particularly vulnerable if exposed to the contaminant 

in their drinking water; 

(5) Whether alternative water supplies should be used; 

(3) Operation under a variance granted under Section 1415 or an exemption 

granted under Section 1416 of the Safe Drinking Water Act;

(4) Availability of unregulated contaminant monitoring results, as required 

under §141.207; and

(5) Exceedance of the fluoride secondary maximum contaminant level 

(SMCL), as required under §141.208.

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(6) What actions consumers should take, including when they should seek medical help, if known; 

(7) What the system is doing to correct the violation or situation; 

(8) When the water system expects to return to compliance or resolve the situation; 

(9) The name, business address, and phone number of the water system owner, operator, or designee 

of the public water system as a source of additional information concerning the notice; and 

(10) A statement to encourage the notice recipient to distribute the public notice to other persons served, 

using the standard language under paragraph (d)(3) of this section, where applicable. 

(b) What elements must be included in the public notice for public water systems operating under a 

variance or exemption? (1) If a public water system has been granted a variance or an exemption, the 

public notice must contain: 

(i) An explanation of the reasons for the variance or exemption; 

(ii) The date on which the variance or exemption was issued; 

(iii) A brief status report on the steps the system is taking to install treatment, find alternative sources of 

water, or otherwise comply with the terms and schedules of the variance or exemption; and 

(iv) A notice of any opportunity for public input in the review of the variance or exemption. 

(2) If a public water system violates the conditions of a variance or exemption, the public notice must 

contain the ten elements listed in paragraph (a) of this section. 

(c) How is the public notice to be presented? (1) Each public notice required by this section: 

(i) Must be displayed in a conspicuous way when printed or posted; 

(ii) Must not contain overly technical language or very small print; 

(iii) Must not be formatted in a way that defeats the purpose of the notice; 

(iv) Must not contain language which nullifies the purpose of the notice. 

(2) Each public notice required by this section must comply with multilingual requirements, as follows: 

(i) For public water systems serving a large proportion of non-English speaking consumers, as 

determined by the primacy agency, the public notice must contain information in the appropriate 

language(s) regarding the importance of the notice or contain a telephone number or address where 

persons served may contact the water system to obtain a translated copy of the notice or to request 

assistance in the appropriate language. 

(ii) In cases where the primacy agency has not determined what constitutes a large proportion of nonEnglish speaking consumers, the public water system must include in the public notice the same 

information as in paragraph (c)(2)(i) of this section, where appropriate to reach a large proportion of nonEnglish speaking persons served by the water system. 

(d) What standard language must public water systems include in their public notice? Public water 

systems are required to include the following standard language in their public notice: 

(1) Standard health effects language for MCL or MRDL violations, treatment technique violations, and 

violations of the condition of a variance or exemption. Public water systems must include in each public 

notice the health effects language specified in appendix B to this subpart corresponding to each MCL, 

MRDL, and treatment technique violation listed in appendix A to this subpart, and for each violation of a 

condition of a variance or exemption. 

(2) Standard language for monitoring and testing procedure violations. Public water systems must 

include the following language in their notice, including the language necessary to fill in the blanks, for 

all monitoring and testing procedure violations listed in appendix A to this subpart: 

We are required to monitor your drinking water for specific contaminants on a regular basis. 

Results of regular monitoring are an indicator of whether or not your drinking water meets 

health standards. During [compliance period], we “did not monitor or test” or “did not complete 

all monitoring or testing” for [contaminant(s)], and therefore cannot be sure of the quality of 

your drinking water during that time. 

(3) Standard language to encourage the distribution of the public notice to all persons served. Public 

water systems must include in their notice the following language (where applicable): 

Please share this information with all the other people who drink this water, especially those 

who may not have received this notice directly (for example, people in apartments, nursing 

homes, schools, and businesses). You can do this by posting this notice in a public place or 

distributing copies by hand or mail. 

§ 141.206 Notice to new billing units or new customers. 

 top

(a) What is the requirement for community water systems? Community water systems must give a copy 

of the most recent public notice for any continuing violation, the existence of a variance or exemption, or 

other ongoing situations requiring a public notice to all new billing units or new customers prior to or at 

the time service begins. 

(b) What is the requirement for non-community water systems? Non-community water systems must 

continuously post the public notice in conspicuous locations in order to inform new consumers of any 

continuing violation, variance or exemption, or other situation requiring a public notice for as long as the 

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violation, variance, exemption, or other situation persists. 

§ 141.207 Special notice of the availability of unregulated contaminant monitoring 

results. 

 top

(a) When is the special notice to be given? The owner or operator of a community water system or nontransient, non-community water system required to monitor under §141.40 must notify persons served 

by the system of the availability of the results of such sampling no later than 12 months after the 

monitoring results are known. 

(b) What is the form and manner of the special notice? The form and manner of the public notice must 

follow the requirements for a Tier 3 public notice prescribed in §§141.204(c), (d)(1), and (d)(3). The 

notice must also identify a person and provide the telephone number to contact for information on the 

monitoring results. 

§ 141.208 Special notice for exceedance of the SMCL for fluoride. 

 top

(a) When is the special notice to be given? Community water systems that exceed the fluoride 

secondary maximum contaminant level (SMCL) of 2 mg/l as specified in §143.3 (determined by the last 

single sample taken in accordance with §141.23), but do not exceed the maximum contaminant level 

(MCL) of 4 mg/l for fluoride (as specified in §141.62), must provide the public notice in paragraph (c) of 

this section to persons served. Public notice must be provided as soon as practical but no later than 12 

months from the day the water system learns of the exceedance. A copy of the notice must also be sent 

to all new billing units and new customers at the time service begins and to the State public health 

officer. The public water system must repeat the notice at least annually for as long as the SMCL is 

exceeded. If the public notice is posted, the notice must remain in place for as long as the SMCL is 

exceeded, but in no case less than seven days (even if the exceedance is eliminated). On a case-bycase basis, the primacy agency may require an initial notice sooner than 12 months and repeat notices 

more frequently than annually. 

(b) What is the form and manner of the special notice? The form and manner of the public notice 

(including repeat notices) must follow the requirements for a Tier 3 public notice in §141.204(c) and (d)

(1) and (d)(3). 

(c) What mandatory language must be contained in the special notice? The notice must contain the 

following language, including the language necessary to fill in the blanks: 

This is an alert about your drinking water and a cosmetic dental problem that might affect 

children under nine years of age. At low levels, fluoride can help prevent cavities, but children 

drinking water containing more than 2 milligrams per liter (mg/l) of fluoride may develop 

cosmetic discoloration of their permanent teeth (dental fluorosis). The drinking water provided 

by your community water system [ name ] has a fluoride concentration of [ insert value ] mg/l. 

Dental fluorosis, in its moderate or severe forms, may result in a brown staining and/or pitting 

of the permanent teeth. This problem occurs only in developing teeth, before they erupt from 

the gums. Children under nine should be provided with alternative sources of drinking water 

or water that has been treated to remove the fluoride to avoid the possibility of staining and 

pitting of their permanent teeth. You may also want to contact your dentist about proper use 

by young children of fluoride-containing products. Older children and adults may safely drink 

the water. 

Drinking water containing more than 4 mg/L of fluoride (the U.S. Environmental Protection 

Agency's drinking water standard) can increase your risk of developing bone disease. Your 

drinking water does not contain more than 4 mg/l of fluoride, but we're required to notify you 

when we discover that the fluoride levels in your drinking water exceed 2 mg/l because of this 

cosmetic dental problem. 

For more information, please call [name of water system contact] of [name of community 

water system] at [phone number]. Some home water treatment units are also available to 

remove fluoride from drinking water. To learn more about available home water treatment 

units, you may call NSF International at 1–877–8–NSF–HELP.” 

§ 141.209 Special notice for nitrate exceedances above MCL by non-community water 

systems (NCWS), where granted permission by the primacy agency under §141.11(d) 

 top

(a) When is the special notice to be given? The owner or operator of a non-community water system 

granted permission by the primacy agency under §141.11(d) to exceed the nitrate MCL must provide 

notice to persons served according to the requirements for a Tier 1 notice under §141.202(a) and (b). 

(b) What is the form and manner of the special notice? Non-community water systems granted 

permission by the primacy agency to exceed the nitrate MCL under §141.11(d) must provide continuous 

posting of the fact that nitrate levels exceed 10 mg/l and the potential health effects of exposure, 

according to the requirements for Tier 1 notice delivery under §141.202(c) and the content requirements 

under §141.205. 

§ 141.210 Notice by primacy agency on behalf of the public water system. 

 top

(a) May the primacy agency give the notice on behalf of the public water system? The primacy agency 

may give the notice required by this subpart on behalf of the owner and operator of the public water 

system if the primacy agency complies with the requirements of this subpart. 

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(b) What is the responsibility of the public water system when notice is given by the primacy agency? 

The owner or operator of the public water system remains responsible for ensuring that the requirements 

of this subpart are met. 

§ 141.211 Special notice for repeated failure to conduct monitoring of the source 

water for Cryptosporidium and for failure to determine bin classification or mean 

Cryptosporidium level. 

 top

(a) When is the special notice for repeated failure to monitor to be given? The owner or operator of a 

community or non-community water system that is required to monitor source water under §141.701 

must notify persons served by the water system that monitoring has not been completed as specified no 

later than 30 days after the system has failed to collect any 3 months of monitoring as specified in 

§141.701(c). The notice must be repeated as specified in §141.203(b). 

(b) When is the special notice for failure to determine bin classification or mean Cryptosporidium level to 

be given? The owner or operator of a community or non-community water system that is required to 

determine a bin classification under §141.710, or to determine mean Cryptosporidium level under 

§141.712, must notify persons served by the water system that the determination has not been made as 

required no later than 30 days after the system has failed report the determination as specified in 

§141.710(e) or §141.712(a), respectively. The notice must be repeated as specified in §141.203(b). The 

notice is not required if the system is complying with a State-approved schedule to address the violation. 

(c) What is the form and manner of the special notice? The form and manner of the public notice must 

follow the requirements for a Tier 2 public notice prescribed in §141.203(c). The public notice must be 

presented as required in §141.205(c). 

(d) What mandatory language must be contained in the special notice? The notice must contain the 

following language, including the language necessary to fill in the blanks. 

(1) The special notice for repeated failure to conduct monitoring must contain the following language: 

We are required to monitor the source of your drinking water for Cryptosporidium. Results of 

the monitoring are to be used to determine whether water treatment at the (treatment plant 

name) is sufficient to adequately remove Cryptosporidium from your drinking water. We are 

required to complete this monitoring and make this determination by (required bin 

determination date). We “did not monitor or test” or “did not complete all monitoring or testing” 

on schedule and, therefore, we may not be able to determine by the required date what 

treatment modifications, if any, must be made to ensure adequate Cryptosporidium removal. 

Missing this deadline may, in turn, jeopardize our ability to have the required treatment 

modifications, if any, completed by the deadline required, (date). 

For more information, please call (name of water system contact) of (name of water system) 

at (phone number). 

(2) The special notice for failure to determine bin classification or mean Cryptosporidium level must 

contain the following language: 

We are required to monitor the source of your drinking water for Cryptosporidium in order to 

determine by (date) whether water treatment at the (treatment plant name) is sufficient to 

adequately remove Cryptosporidium from your drinking water. We have not made this 

determination by the required date. Our failure to do this may jeopardize our ability to have 

the required treatment modifications, if any, completed by the required deadline of (date). For 

more information, please call (name of water system contact) of (name of water system) at 

(phone number). 

(3) Each special notice must also include a description of what the system is doing to correct the 

violation and when the system expects to return to compliance or resolve the situation. 

[71 FR 768, Jan. 5, 2006] 

Appendix A to Subpart Q of Part 141—NPDWR Violations and Other Situations 

Requiring Public Notice1

 top

Contaminant

MCL/MRDL/TT 

violations2

Monitoring & 

testing 

procedure 

violations

Tier of 

public 

notice 

required Citation

Tier of 

public 

notice 

required Citation

I. Violations of National Primary 

Drinking Water Regulations 

(NPDWR):3

A. Microbiological 

Contaminants

1. Total coliform 2 141.63(a) 3 141.21

(a)–(e)

2. Fecal coliform/E. 

coli

1 141.63(b) 41, 3 141.21

(e)

3. Turbidity MCL 2 141.13(a) 3 141.22

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4. Turbidity MCL 

(average of 2 days' 

samples >5 NTU)

52, 1 141.13(b) 3 141.22

5. Turbidity (for TT 

violations resulting 

from a single 

exceedance of 

maximum allowable 

turbidity level)

62, 1 141.71(a)(2), 

141.71(c)(2)(i), 

141.73(a)(2), 

141.73 (b)(2), 

141.73 (c)(2), 

141.73(d), 

141.173(a)(2), 

141.173(b), 

141.551(b)

3 141.74

(a)(1), 

141.74

(b)(2), 

141.74

(c)(1), 

141.174, 

141.560

(a)–(c), 

141.561.

6. Surface Water 

Treatment Rule 

violations, other than 

violations resulting 

from single 

exceedance of max. 

allowable turbidity 

level (TT)

2 141.70–141.73 3 141.74

7. Interim Enhanced 

Surface Water 

Treatment Rule 

violations, other than 

violations resulting 

from single 

exceedance of max. 

turbidity level (TT)

72 141.170–

141.173, 

141.500–

141.553

3 141.172, 

141.174, 

141.530–

141.544, 

141.560–

141.564.

8. Filter Backwash 

Recycling Rule 

violations

2 141.76(c) 3 141.76

(b), (d)

9. Long Term 1 

Enhanced Surface 

Water Treatment Rule 

violations

2 141.500–

141.553

3 141.530–

141.544, 

141.560–

141.564.

10. LT2ESWTR 

violations

2 141.710–

141.720

222, 3 141.701–

141.705 

and 

141.708–

141.709.

11. Ground Water 

Rule violations

2 141.404 3 141.402

(h),

141.403

(d).

B. Inorganic Chemicals (IOCs)

1. Antimony 2 141.62(b) 3 141.23

(a), (c)

2. Arsenic 2 8141.62(b) 3 11141.23

(a), (c)

3. Asbestos (fibers 

>10 μm)

2 141.62(b) 3 141.23

(a)–(b)

4. Barium 2 141.62(b) 3 141.23

(a), (c)

5. Beryllium 2 141.62(b) 3 141.23

(a), (c)

6. Cadmium 2 141.62(b) 3 141.23

(a), (c)

7. Chromium (total) 2 141.62(b) 3 141.23

(a), (c)

8. Cyanide 2 141.62(b) 3 141.23

(a), (c)

9. Fluoride 2 141.62(b) 3 141.23

(a), (c)

10. Mercury 

(inorganic)

2 141.62(b) 3 141.23

(a), (c)

11. Nitrate 1 141.62(b) 121, 3 141.23

(a), (d), 

141.23(f)

(2)

12. Nitrite 1 141.62(b) 121, 3 141.23

(a), (e), 

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141.23(f)

(2)

13. Total Nitrate and 

Nitrite

1 141.62(b) 3 141.23

(a)

14. Selenium 2 141.62(b) 3 141.23

(a), (c)

15. Thallium 2 141.62(b) 3 141.23

(a), (c)

C. Lead and Copper Rule 

(Action Level for lead is 0.015 

mg/L, for copper is 1.3 mg/L)

1. Lead and Copper 

Rule (TT)

2 141.80–141.85 3 141.86–

141.89

D. Synthetic Organic 

Chemicals (SOCs)

1. 2,4–D 2 141.61(c) 3 141.24

(h)

2. 2,4,5–TP (Silvex) 2 141.61(c) 3 141.24

(h)

3. Alachlor 2 141.61(c) 3 141.24

(h)

4. Atrazine 2 141.61(c) 3 141.24

(h)

5. Benzo(a)pyrene 

(PAHs)

2 141.61(c) 3 141.24

(h)

6. Carbofuran 2 141.61(c) 3 141.24

(h)

7. Chlordane 2 141.61(c) 3 141.24

(h)

8. Dalapon 2 141.61(c) 3 141.24

(h)

9. Di (2-ethylhexyl) 

adipate

2 141.61(c) 3 141.24

(h)

10. Di (2-ethylhexyl) 

phthalate

2 141.61(c) 3 141.24

(h)

11. 

Dibromochloropropane

2 141.61(c) 3 141.24

(h)

12. Dinoseb 2 141.61(c) 3 141.24

(h)

13. Dioxin (2,3,7,8-

TCDD)

2 141.61(c) 3 141.24

(h)

14. Diquat 2 141.61(c) 3 141.24

(h)

15. Endothall 2 141.61(c) 3 141.24

(h)

16. Endrin 2 141.61(c) 3 141.24

(h)

17. Ethylene 

dibromide

2 141.61(c) 3 141.24

(h)

18. Glyphosate 2 141.61(c) 3 141.24

(h)

19. Heptachlor 2 141.61(c) 3 141.24

(h)

20. Heptachlor 

epoxide

2 141.61(c) 3 141.24

(h)

21. 

Hexachlorobenzene

2 141.61(c) 3 141.24

(h)

22. Hexachlorocyclopentadiene2 141.61(c) 3 141.24

(h)

23. Lindane 2 141.61(c) 3 141.24

(h)

24. Methoxychlor 2 141.61(c) 3 141.24

(h)

25. Oxamyl (Vydate) 2 141.61(c) 3 141.24

(h)

26. Pentachlorophenol 2 141.61(c) 3 141.24

(h)

27. Picloram 2 141.61(c) 3 141.24

(h)

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28. Polychlorinated 

biphenyls (PCBs)

2 141.61(c) 3 141.24

(h)

29. Simazine 2 141.61(c) 3 141.24

(h)

30. Toxaphene 2 141.61(c) 3 141.24

(h)

E. Volatile Organic Chemicals 

(VOCs)

1. Benzene 2 141.61(a) 3 141.24(f)

2. Carbon tetrachloride 2 141.61(a) 3 141.24(f)

3. Chlorobenzene 

(monochlorobenzene)

2 141.61(a) 3 141.24(f)

4. o-Dichlorobenzene 2 141.61(a) 3 141.24(f)

5. p-Dichlorobenzene 2 141.61(a) 3 141.24(f)

6. 1,2-Dichloroethane 2 141.61(a) 3 141.24(f)

7. 1,1-

Dichloroethylene

2 141.61(a) 3 141.24(f)

8. cis-1,2-

Dichloroethylene

2 141.61(a) 3 141.24(f)

9. trans-1,2-

Dichloroethylene

2 141.61(a) 3 141.24(f)

10. Dichloromethane 2 141.61(a) 3 141.24(f)

11. 1,2-

Dichloropropane

2 141.61(a) 3 141.24(f)

12. Ethylbenzene 2 141.61(a) 3 141.24(f)

13. Styrene 2 141.61(a) 3 141.24(f)

14. 

Tetrachloroethylene

2 141.61(a) 3 141.24(f)

15. Toluene 2 141.61(a) 3 141.24(f)

16. 1,2,4-

Trichlorobenzene

2 141.61(a) 3 141.24(f)

17. 1,1,1-

Trichloroethane

2 141.61(a) 3 141.24(f)

18. 1,1,2-

Trichloroethane

2 141.61(a) 3 141.24(f)

19. Trichloroethylene 2 141.61(a) 3 141.24(f)

20. Vinyl chloride 2 141.61(a) 3 141.24(f)

21. Xylenes (total) 2 141.61(a) 3 141.24(f)

F. Radioactive Contaminants

1. Beta/photon 

emitters

2 141.66(d) 3 141.25

(a)

141.26

(b)

2. Alpha emitters 2 141.66(c) 3 141.25

(a)

141.26

(a)

3. Combined radium 

(226 and 228)

2 141.66(b) 3 141.25

(a)

141.26

(a)

4. Uranium 92 141.66(e) 103 141.25

(a)

141.26

(a)

G. Disinfection Byproducts 

(DBPs), Byproduct Precursors, 

Disinfectant Residuals. Where 

disinfection is used in the 

treatment of drinking water, 

disinfectants combine with 

organic and inorganic matter 

present in water to form 

chemicals called disinfection 

byproducts (DBPs). EPA sets 

standards for controlling the 

levels of disinfectants and 

DBPs in drinking water, 

including trihalomethanes 

(THMs) and haloacetic acids 

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(HAAs).13

1. Total 

trihalomethanes 

(TTHMs)

2 14141.64(b) 3 141.132

(a)–(b), 

141.600–

141.605, 

141.620–

141.629

2. Haloacetic Acids 

(HAA5)

2 141.64(b) 3 141.132

(a)–(b), 

141.600–

141.605, 

141.620–

141.629

3. Bromate 2 141.64(a) 3 141.132

(a)–(b)

4. Chlorite 2 141.64(a) 3 141.132

(a)–(b)

5. Chlorine (MRDL) 2 141.65(a) 3 141.132

(a), (c)

6. Chloramine (MRDL) 2 141.65(a) 3 141.132

(a), (c)

7. Chlorine dioxide 

(MRDL), where any 2 

consecutive daily 

samples at entrance to 

distribution system 

only are above MRDL

2 141.65(a), 

141.133(c)(3)

215, 3 141.132

(a), (c), 

141.133

(c)(2)

8. Chlorine dioxide 

(MRDL), where 

sample(s) in 

distribution system the 

next day are also 

above MRDL

161 141.65(a), 

141.133(c)(3)

1 141.132

(a), (c), 

141.133

(c)(2)

9. Control of DBP 

precursors—TOC (TT)

2 141.135(a)–(b) 3 141.132

(a), (d)

10. Bench marking 

and disinfection 

profiling

N/A N/A 3 141.172 

141.530–

141.544.

11. Development of 

monitoring plan

N/A N/A 3 141.132

(f)

H. Other Treatment Techniques

1. Acrylamide (TT) 2 141.111 N/A N/A

2. Epichlorohydrin (TT) 2 141.111 N/A N/A

II. Unregulated Contaminant 

Monitoring:17

A. Unregulated contaminants N/A N/A 3 141.40

B. Nickel N/A N/A 3 141.23

(c), (k)

III. Public Notification for 

Variances and Exemptions:

A. Operation under a variance 

or exemption

3 181415, 1416, N/A N/A

B. Violation of conditions of a 

variance or exemption

2 1415, 

1416,19142.307

N/A N/A

IV. Other Situations Requiring 

Public Notification:

A. Fluoride secondary 

maximum contaminant level 

(SMCL) exceedance

3 143.3 N/A N/A

B. Exceedance of nitrate MCL 

for non-community systems, as 

allowed by primacy agency

1 141.11(d) N/A N/A

C. Availability of unregulated 

contaminant monitoring data

3 141.40 N/A N/A

D. Waterborne disease 

outbreak

1 141.2, 141.71

(c)(2)(ii)

N/A N/A

E. Other waterborne 

emergency20

1 N/A N/A N/A

F. Source Water Sample 

Positive for GWR Fecal 

1 141.402(g) N/A N/A

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Appendix A—Endnotes 

1. Violations and other situations not listed in this table (e.g., failure to prepare Consumer Confidence 

Reports), do not require notice, unless otherwise determined by the primary agency. Primacy agencies 

may, at their option, also require a more stringent public notice tier (e.g., Tier 1 instead of Tier 2 or Tier 2 

instead of Tier 3) for specific violations and situations listed in this Appendix, as authorized under 

§141.202(a) and §141.203(a). 

2. MCL—Maximum contaminant level, MRDL—Maximum residual disinfectant level, TT—Treatment 

technique 

3. The term Violations of National Primary Drinking Water Regulations (NPDWR) is used here to include 

violations of MCL, MRDL, treatment technique, monitoring, and testing procedure requirements. 

4. Failure to test for fecal coliform or E. coli is a Tier 1 violation if testing is not done after any repeat 

sample tests positive for coliform. All other total coliform monitoring and testing procedure violations are 

Tier 3. 

5. Systems that violate the turbidity MCL of 5 NTU based on an average of measurements over two 

consecutive days must consult with the primacy agency within 24 hours after learning of the violation. 

Based on this consultation, the primacy agency may subsequently decide to elevate the violation to Tier 

1. If a system is unable to make contact with the primacy agency in the 24-hour period, the violation is 

automatically elevated to Tier 1. 

6. Systems with treatment technique violations involving a single exceedance of a maximum turbidity 

limit under the Surface Water Treatment Rule (SWTR), the Interim Enhanced Surface Water Treatment 

Rule (IESWTR), or the Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) are 

required to consult with the primacy agency within 24 hours after learning of the violation. Based on this 

consultation, the primacy agency may subsequently decide to elevate the violation to Tier 1. If a system 

is unable to make contact with the primacy agency in the 24-hour period, the violation is automatically 

elevated to Tier 1. 

7. Most of the requirements of the Interim Enhanced Surface Water Treatment Rule (63 FR 69477) 

(§§141.170–141.171, 141.173–141.174) become effective January 1, 2002 for Subpart H systems 

(surface water systems and ground water systems under the direct influence of surface water) serving at 

least 10,000 persons. However, §141.172 has some requirements that become effective as early as 

April 16, 1999. The Surface Water Treatment Rule remains in effect for systems serving at least 10,000 

persons even after 2002; the Interim Enhanced Surface Water Treatment Rule adds additional 

requirements and does not in many cases supercede the SWTR. 

8. The arsenic MCL citations are effective January 23, 2006. Until then, the citations are §141.11(b) and 

§141.23(n). 

9. The uranium MCL Tier 2 violation citations are effective December 8, 2003 for all community water 

systems. 

10. The uranium Tier 3 violation citations are effective December 8, 2000 for all community water 

systems. 

11. The arsenic Tier 3 violation MCL citations are effective January 23, 2006. Until then, the citations are 

§141.23(a), (l). 

12. Failure to take a confirmation sample within 24 hours for nitrate or nitrite after an initial sample 

exceeds the MCL is a Tier 1 violation. Other monitoring violations for nitrate are Tier 3. 

13. Subpart H community and non-transient non-community systems serving ≥10,000 must comply with 

new DBP MCLs, disinfectant MRDLs, and related monitoring requirements beginning January 1, 2002. 

All other community and non-transient non-community systems must meet the MCLs and MRDLs 

beginning January 1, 2004. Subpart H transient non-community systems serving 10,000 or more 

persons and using chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide 

MRDL beginning January 1, 2002. Subpart H transient non-community systems serving fewer than 

10,000 persons and using only ground water not under the direct influence of surface water and using 

chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning 

January 1, 2004. 

14. §§141.64(b)(1) 141.132(a)–(b) apply until §§141.620–141.630 take effect under the schedule in 

§141.620(c). 

15. Failure to monitor for chlorine dioxide at the entrance to the distribution system the day after 

exceeding the MRDL at the entrance to the distribution system is a Tier 2 violation. 

16. If any daily sample taken at the entrance to the distribution system exceeds the MRDL for chlorine 

dioxide and one or more samples taken in the distribution system the next day exceed the MRDL, Tier 1 

notification is required. Failure to take the required samples in the distribution system after the MRDL is 

exceeded at the entry point also triggers Tier 1 notification. 

17. Some water systems must monitor for certain unregulated contaminants listed in §141.40. 

18. This citation refers to §§1415 and 1416 of the Safe Drinking Water Act. §§1415 and 1416 require 

that “a schedule prescribed. . . for a public water system granted a variance [or exemption] shall require 

compliance by the system. . .” 

19. In addition to §§1415 and 1416 of the Safe Drinking Water Act, 40 CFR 142.307 specifies the items 

and schedule milestones that must be included in a variance for small systems. 

20. Other waterborne emergencies require a Tier 1 public notice under §141.202(a) for situations that do 

not meet the definition of a waterborne disease outbreak given in 40 CFR 141.2 but that still have the 

indicators: E. coli, enterococci, 

or coliphage

G. Other situations as 

determined by primacy agency

211, 2, 3 N/A N/A N/A

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potential to have serious adverse effects on health as a result of short-term exposure. These could 

include outbreaks not related to treatment deficiencies, as well as situations that have the potential to 

cause outbreaks, such as failures or significant interruption in water treatment processes, natural 

disasters that disrupt the water supply or distribution system, chemical spills, or unexpected loading of 

possible pathogens into the source water. 

21. Primacy agencies may place other situations in any tier they believe appropriate, based on threat to 

public health. 

22. Failure to collect three or more samples for Cryptosporidium analysis is a Tier 2 violation requiring 

special notice as specified in §141.211. All other monitoring and testing procedure violations are Tier 3. 

[65 FR 26035, May 4, 2000, as amended at 65 FR 76750, Dec.7, 2000; 66 FR 7065, Jan. 22, 2001; 66 

FR 31104, June 8, 2001; 67 FR 1836, Jan. 14, 2002; 69 FR 38856, June 29, 2004; 71 FR 483, Jan. 4, 

2006; 71 FR 768, Jan. 5, 2006; 71 FR 65652, Nov. 8, 2006] 

Appendix B to Subpart Q of Part 141—Standard Health Effects Language for Public 

Notification 

 top

Contaminant MCLG1mg/L MCL2mg/L

Standard health effects 

language for public 

notification

National Primary Drinking Water Regulations (NPDWR)

A. Microbiological Contaminants

1a. Total coliform Zero See 

footnote3

Coliforms are bacteria that 

are naturally present in the 

environment and are used 

as an indicator that other, 

potentially-harmful, 

bacteria may be present. 

Coliforms were found in 

more samples than 

allowed and this was a 

warning of potential 

problems.

1b. Fecal coliform/E. coli Zero Zero Fecal coliforms and E. coli 

are bacteria whose 

presence indicates that the 

water may be 

contaminated with human 

or animal wastes. Microbes 

in these wastes can cause 

short-term effects, such as 

diarrhea, cramps, nausea, 

headaches, or other 

symptoms. They may pose 

a special health risk for 

infants, young children, 

some of the elderly, and 

people with severely 

compromised immune 

systems.

1c. Fecal indicators (GWR): 

i. E. coli 

ii. enterococci 

iii. coliphage

Zero 

None 

None

TT 

TT 

TT

Fecal indicators are 

microbes whose presence 

indicates that the water 

may be contaminated with 

human or animal wastes. 

Microbes in these wastes 

can cause short-term 

health effects, such as 

diarrhea, cramps, nausea, 

headaches, or other 

symptoms. They may pose 

a special health risk for 

infants, young children, 

some of the elderly, and 

people with severely 

compromised immune 

systems.

1d. Ground Water Rule 

(GWR) TT violations

None TT Inadequately treated or 

inadequately protected 

water may contain 

disease-causing 

organisms. These 

organisms can cause 

symptoms such as 

diarrhea, nausea, cramps, 

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and associated 

headaches.

2a. Turbidity (MCL)4 None 1 NTU5/5 

NTU

Turbidity has no health 

effects. However, turbidity 

can interfere with 

disinfection and provide a 

medium for microbial 

growth. Turbidity may 

indicate the presence of 

disease-causing 

organisms. These 

organisms include 

bacteria, viruses, and 

parasites that can cause 

symptoms such as nausea, 

cramps, diarrhea and 

associated headaches.

2b. Turbidity (SWTR TT)6 None TT7 Turbidity has no health 

effects. However, turbidity 

can interfere with 

disinfection and provide a 

medium for microbial 

growth. Turbidity may 

indicate the presence of 

disease-causing 

organisms. These 

organisms include 

bacteria, viruses, and 

parasites that can cause 

symptoms such as nausea, 

cramps, diarrhea and 

associated headaches.

2c. Turbidity (IESWTR TT 

and LT1ESWTR TT)8

None TT Turbidity has no health 

effects. However, turbidity 

can interfere with 

disinfection and provide a 

medium for microbial 

growth. Turbidity may 

indicate the presence of 

disease-causing 

organisms. These 

organisms include 

bacteria, viruses, and 

parasites that can cause 

symptoms such as nausea, 

cramps, diarrhea and 

associated headaches.

B. Surface Water Treatment Rule (SWTR), Interim Enhanced Surface Water 

Treatment Rule (IESWTR), Long Term 1 Enhanced Surface Water Treatment Rule 

(LT1ESWTR) and the Filter Backwash Recycling Rule (FBRR) violations

3. Giardia lamblia 

(SWTR/IESWTR/LT1ESWTR)

Zero TT10 Inadequately treated water 

may contain diseasecausing organisms. These 

organisms include 

bacteria, viruses, and 

parasites which can cause 

symptoms such as nausea, 

cramps, diarrhea, and 

associated headaches.

4. Viruses 

(SWTR/IESWTR/LT1ESWTR)

5. Heterotrophic plate count 

(HPC) bacteria9

(SWTR/IESWTR/LT1ESWTR)

6. Legionella 

(SWTR/IESWTR/LT1ESWTR)

7. Cryptosporidium 

(IESWTR/FBRR/LT1ESWTR)

C. Inorganic Chemicals (IOCs)

8. Antimony 0.006 0.006 Some people who drink 

water containing antimony 

well in excess of the MCL 

over many years could 

experience increases in 

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blood cholesterol and 

decreases in blood sugar.

9. Arsenic11 0 0.010 Some people who drink 

water containing arsenic in 

excess of the MCL over 

many years could 

experience skin damage or 

problems with their 

circulatory system, and 

may have an increased 

risk of getting cancer.

10. Asbestos (10 μm) 7 MFL12 7 MFL Some people who drink 

water containing asbestos 

in excess of the MCL over 

many years may have an 

increased risk of 

developing benign 

intestinal polyps.

11. Barium 2 2 Some people who drink 

water containing barium in 

excess of the MCL over 

many years could 

experience an increase in 

their blood pressure.

12. Beryllium 0.004 0.004 Some people who drink 

water containing beryllium 

well in excess of the MCL 

over many years could 

develop intestinal lesions.

13. Cadmium 0.005 0.005 Some people who drink 

water containing cadmium 

in excess of the MCL over 

many years could 

experience kidney 

damage.

14. Chromium (total) 0.1 0.1 Some people who use 

water containing chromium 

well in excess of the MCL 

over many years could 

experience allergic 

dermatitis.

15. Cyanide 0.2 0.2 Some people who drink 

water containing cyanide 

well in excess of the MCL 

over many years could 

experience nerve damage 

or problems with their 

thyroid.

16. Fluoride 4.0 4.0 Some people who drink 

water containing fluoride in 

excess of the MCL over 

many years could get bone 

disease, including pain and 

tenderness of the bones. 

Fluoride in drinking water 

at half the MCL or more 

may cause mottling of 

children's teeth, usually in 

children less than nine 

years old. Mottling, also 

known as dental fluorosis, 

may include brown staining 

and/or pitting of the teeth, 

and occurs only in 

developing teeth before 

they erupt from the gums.

17. Mercury (inorganic) 0.002 0.002 Some people who drink 

water containing inorganic 

mercury well in excess of 

the MCL over many years 

could experience kidney 

damage.

18. Nitrate 10 10 Infants below the age of six 

months who drink water 

containing nitrate in excess 

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of the MCL could become 

seriously ill and, if 

untreated, may die. 

Symptoms include 

shortness of breath and 

blue baby syndrome.

19. Nitrite 1 1 Infants below the age of six 

months who drink water 

containing nitrite in excess 

of the MCL could become 

seriously ill and, if 

untreated, may die. 

Symptoms include 

shortness of breath and 

blue baby syndrome.

20. Total Nitrate and Nitrite 10 10 Infants below the age of six 

months who drink water 

containing nitrate and 

nitrite in excess of the MCL 

could become seriously ill 

and, if untreated, may die. 

Symptoms include 

shortness of breath and 

blue baby syndrome.

21. Selenium 0.05 0.05 Selenium is an essential 

nutrient. However, some 

people who drink water 

containing selenium in 

excess of the MCL over 

many years could 

experience hair or 

fingernail losses, 

numbness in fingers or 

toes, or problems with their 

circulation.

22. Thallium 0.0005 0.002 Some people who drink 

water containing thallium in 

excess of the MCL over 

many years could 

experience hair loss, 

changes in their blood, or 

problems with their 

kidneys, intestines, or liver.

D. Lead and Copper Rule

23. Lead Zero TT13 Infants and children who 

drink water containing lead 

in excess of the action 

level could experience 

delays in their physical or 

mental development. 

Children could show slight 

deficits in attention span 

and learning abilities. 

Adults who drink this water 

over many years could 

develop kidney problems 

or high blood pressure.

24. Copper 1.3 TT14 Copper is an essential 

nutrient, but some people 

who drink water containing 

copper in excess of the 

action level over a 

relatively short amount of 

time could experience 

gastrointestinal distress. 

Some people who drink 

water containing copper in 

excess of the action level 

over many years could 

suffer liver or kidney 

damage. People with 

Wilson's Disease should 

consult their personal 

doctor.

E. Synthetic Organic Chemicals (SOCs)

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25. 2,4–D 0.07 0.07 Some people who drink 

water containing the weed 

killer 2,4–D well in excess 

of the MCL over many 

years could experience 

problems with their 

kidneys, liver, or adrenal 

glands.

26. 2,4,5–TP (Silvex) 0.05 0.05 Some people who drink 

water containing silvex in 

excess of the MCL over 

many years could 

experience liver problems.

27. Alachlor Zero 0.002 Some people who drink 

water containing alachlor in 

excess of the MCL over 

many years could have 

problems with their eyes, 

liver, kidneys, or spleen, or 

experience anemia, and 

may have an increased 

risk of getting cancer.

28. Atrazine 0.003 0.003 Some people who drink 

water containing atrazine 

well in excess of the MCL 

over many years could 

experience problems with 

their cardiovascular system 

or reproductive difficulties.

29. Benzo(a)pyrene (PAHs) Zero 0.0002 Some people who drink 

water containing benzo(a)

pyrene in excess of the 

MCL over many years may 

experience reproductive 

difficulties and may have 

an increased risk of getting 

cancer.

30. Carbofuran 0.04 0.04 Some people who drink 

water containing 

carbofuran in excess of the 

MCL over many years 

could experience problems 

with their blood, or nervous 

or reproductive systems.

31. Chlordane Zero 0.002 Some people who drink 

water containing chlordane 

in excess of the MCL over 

many years could 

experience problems with 

their liver or nervous 

system, and may have an 

increased risk of getting 

cancer.

32. Dalapon 0.2 0.2 Some people who drink 

water containing dalapon 

well in excess of the MCL 

over many years could 

experience minor kidney 

changes.

33. Di(2-ethylhexyl) adipate 0.4 0.4 Some people who drink 

water containing di(2-

ethylhexyl) adipate well in 

excess of the MCL over 

many years could 

experience toxic effects 

such as weight loss, liver 

enlargement or possible 

reproductive difficulties.

34. Di(2-ethylhexyl) phthalate Zero 0.006 Some people who drink 

water containing di(2-

ethylhexyl) phthalate well 

in excess of the MCL over 

many years may have 

problems with their liver, or 

experience reproductive 

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difficulties, and may have 

an increased risk of getting 

cancer.

35. Dibromochloropropane 

(DBCP)

Zero 0.0002 Some people who drink 

water containing DBCP in 

excess of the MCL over 

many years could 

experience reproductive 

difficulties and may have 

an increased risk of getting 

cancer.

36. Dinoseb 0.007 0.007 Some people who drink 

water containing dinoseb 

well in excess of the MCL 

over many years could 

experience reproductive 

difficulties.

37. Dioxin (2,3,7,8-TCDD) Zero 3×10−8 Some people who drink 

water containing dioxin in 

excess of the MCL over 

many years could 

experience reproductive 

difficulties and may have 

an increased risk of getting 

cancer.

38. Diquat 0.02 0.02 Some people who drink 

water containing diquat in 

excess of the MCL over 

many years could get 

cataracts.

39. Endothall 0.1 0.1 Some people who drink 

water containing endothall 

in excess of the MCL over 

many years could 

experience problems with 

their stomach or intestines.

40. Endrin 0.002 0.002 Some people who drink 

water containing endrin in 

excess of the MCL over 

many years could 

experience liver problems.

41. Ethylene dibromide Zero 0.00005 Some people who drink 

water containing ethylene 

dibromide in excess of the 

MCL over many years 

could experience problems 

with their liver, stomach, 

reproductive system, or 

kidneys, and may have an 

increased risk of getting 

cancer.

42. Glyphosate 0.7 0.7 Some people who drink 

water containing 

glyphosate in excess of the 

MCL over many years 

could experience problems 

with their kidneys or 

reproductive difficulties.

43. Heptachlor Zero 0.0004 Some people who drink 

water containing 

heptachlor in excess of the 

MCL over many years 

could experience liver 

damage and may have an 

increased risk of getting 

cancer.

44. Heptachlor epoxide Zero 0.0002 Some people who drink 

water containing 

heptachlor epoxide in 

excess of the MCL over 

many years could 

experience liver damage, 

and may have an 

increased risk of getting 

cancer.

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45. Hexachlorobenzene Zero 0.001 Some people who drink 

water containing 

hexachlorobenzene in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys, or 

adverse reproductive 

effects, and may have an 

increased risk of getting 

cancer.

46. Hexachlorocyclopentadiene0.05 0.05 Some people who drink 

water containing 

hexachlorocyclopentadiene 

well in excess of the MCL 

over many years could 

experience problems with 

their kidneys or stomach.

47. Lindane 0.0002 0.0002 Some people who drink 

water containing lindane in 

excess of the MCL over 

many years could 

experience problems with 

their kidneys or liver.

48. Methoxychlor 0.04 0.04 Some people who drink 

water containing 

methoxychlor in excess of 

the MCL over many years 

could experience 

reproductive difficulties.

49. Oxamyl (Vydate) 0.2 0.2 Some people who drink 

water containing oxamyl in 

excess of the MCL over 

many years could 

experience slight nervous 

system effects.

50. Pentachlorophenol Zero 0.001 Some people who drink 

water containing 

pentachlorophenol in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys, and 

may have an increased 

risk of getting cancer.

51. Picloram 0.5 0.5 Some people who drink 

water containing picloram 

in excess of the MCL over 

many years could 

experience problems with 

their liver.

52. Polychlorinated biphenyls 

(PCBs)

Zero 0.0005 Some people who drink 

water containing PCBs in 

excess of the MCL over 

many years could 

experience changes in 

their skin, problems with 

their thymus gland, 

immune deficiencies, or 

reproductive or nervous 

system difficulties, and 

may have an increased 

risk of getting cancer.

53. Simazine 0.004 0.004 Some people who drink 

water containing simazine 

in excess of the MCL over 

many years could 

experience problems with 

their blood.

54. Toxaphene Zero 0.003 Some people who drink 

water containing 

toxaphene in excess of the 

MCL over many years 

could have problems with 

their kidneys, liver, or 

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thyroid, and may have an 

increased risk of getting 

cancer.

F. Volatile Organic Chemicals (VOCs)

55. Benzene Zero 0.005 Some people who drink 

water containing benzene 

in excess of the MCL over 

many years could 

experience anemia or a 

decrease in blood 

platelets, and may have an 

increased risk of getting 

cancer.

56. Carbon tetrachloride Zero 0.005 Some people who drink 

water containing carbon 

tetrachloride in excess of 

the MCL over many years 

could experience problems 

with their liver and may 

have an increased risk of 

getting cancer.

57. Chlorobenzene 

(monochloro- benzene)

0.1 0.1 Some people who drink 

water containing 

chlorobenzene in excess of 

the MCL over many years 

could experience problems 

with their liver or kidneys.

58. o -Dichlorobenzene 0.6 0.6 Some people who drink 

water containing odichlorobenzene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver, kidneys, or 

circulatory systems.

59. p -Dichlorobenzene 0.075 0.075 Some people who drink 

water containing pdichlorobenzene in excess 

of the MCL over many 

years could experience 

anemia, damage to their 

liver, kidneys, or spleen, or 

changes in their blood.

60. 1,2-Dichloroethane Zero 0.005 Some people who drink 

water containing 1,2-

dichloroethane in excess of 

the MCL over many years 

may have an increased 

risk of getting cancer.

61. 1,1-Dichloroethylene 0.007 0.007 Some people who drink 

water containing 1,1-

dichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver.

62. cis -1,2-Dichloroethylene 0.07 0.07 Some people who drink 

water containing cis-1,2-

dichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver.

63. trans -1,2-

Dichloroethylene

0.1 0.1 Some people who drink 

water containing trans-1,2-

dichloroethylene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver.

64. Dichloromethane Zero 0.005 Some people who drink 

water containing 

dichloromethane in excess 

of the MCL over many 

years could have liver 

problems and may have an 

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increased risk of getting 

cancer.

65. 1,2-Dichloropropane Zero 0.005 Some people who drink 

water containing 1,2-

dichloropropane in excess 

of the MCL over many 

years may have an 

increased risk of getting 

cancer.

66. Ethylbenzene 0.7 0.7 Some people who drink 

water containing 

ethylbenzene well in 

excess of the MCL over 

many years could 

experience problems with 

their liver or kidneys.

67. Styrene 0.1 0.1 Some people who drink 

water containing styrene 

well in excess of the MCL 

over many years could 

have problems with their 

liver, kidneys, or circulatory 

system.

68. Tetrachloroethylene Zero 0.005 Some people who drink 

water containing 

tetrachloroethylene in 

excess of the MCL over 

many years could have 

problems with their liver, 

and may have an 

increased risk of getting 

cancer.

69. Toluene 1 1 Some people who drink 

water containing toluene 

well in excess of the MCL 

over many years could 

have problems with their 

nervous system, kidneys, 

or liver.

70. 1,2,4-Trichlorobenzene 0.07 0.07 Some people who drink 

water containing 1,2,4-

trichlorobenzene well in 

excess of the MCL over 

many years could 

experience changes in 

their adrenal glands.

71. 1,1,1-Trichloroethane 0.2 0.2 Some people who drink 

water containing 1,1,1-

trichloroethane in excess 

of the MCL over many 

years could experience 

problems with their liver, 

nervous system, or 

circulatory system.

72. 1,1,2-Trichloroethane 0.003 0.005 Some people who drink 

water containing 1,1,2-

trichloroethane well in 

excess of the MCL over 

many years could have 

problems with their liver, 

kidneys, or immune 

systems.

73. Trichloroethylene Zero 0.005 Some people who drink 

water containing 

trichloroethylene in excess 

of the MCL over many 

years could experience 

problems with their liver 

and may have an 

increased risk of getting 

cancer.

74. Vinyl chloride Zero 0.002 Some people who drink 

water containing vinyl 

chloride in excess of the 

MCL over many years may 

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have an increased risk of 

getting cancer.

75. Xylenes (total) 10 10 Some people who drink 

water containing xylenes in 

excess of the MCL over 

many years could 

experience damage to their 

nervous system.

G. Radioactive Contaminants

76. Beta/photon emitters Zero 4 

mrem/yr15

Certain minerals are 

radioactive and may emit 

forms of radiation known 

as photons and beta 

radiation. Some people 

who drink water containing 

beta and photon emitters in 

excess of the MCL over 

many years may have an 

increased risk of getting 

cancer.

77. Alpha emitters Zero 17 pCi/L17 Certain minerals are 

radioactive and may emit a 

form of radiation known as 

alpha radiation. Some 

people who drink water 

containing alpha emitters 

in excess of the MCL over 

many years may have an 

increased risk of getting 

cancer.

78. Combined radium (226 & 

228)

Zero 5 pCi/L Some people who drink 

water containing radium 

226 or 228 in excess of the 

MCL over many years may 

have an increased risk of 

getting cancer.

79. Uranium16 Zero 30 μg/L Some people who drink 

water containing uranium 

in excess of the MCL over 

many years may have an 

increased risk of getting 

cancer and kidney toxicity.

H. Disinfection Byproducts (DBPs), Byproduct Precursors, and Disinfectant 

Residuals: Where disinfection is used in the treatment of drinking water, 

disinfectants combine with organic and inorganic matter present in water to form 

chemicals called disinfection byproducts (DBPs). EPA sets standards for controlling 

the levels of disinfectants and DBPs in drinking water, including trihalomethanes 

(THMs) and haloacetic acids (HAAs)18

80. Total trihalomethanes 

(TTHMs)

N/A 0.08019,20 Some people who drink 

water containing 

trihalomethanes in excess 

of the MCL over many 

years may experience 

problems with their liver, 

kidneys, or central nervous 

system, and may have an 

increased risk of getting 

cancer.

81. Haloacetic Acids (HAA) N/A 0.06021 Some people who drink 

water containing haloacetic 

acids in excess of the MCL 

over many years may have 

an increased risk of getting 

cancer.

82. Bromate Zero 0.010 Some people who drink 

water containing bromate 

in excess of the MCL over 

many years may have an 

increased risk of getting 

cancer.

83. Chlorite 0.08 1.0 Some infants and young 

children who drink water 

containing chlorite in 

excess of the MCL could 

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experience nervous 

system effects. Similar 

effects may occur in 

fetuses of pregnant women 

who drink water containing 

chlorite in excess of the 

MCL. Some people may 

experience anemia.

84. Chlorine 4 (MRDLG)

22

4.0 

(MRDL)23

Some people who use 

water containing chlorine 

well in excess of the MRDL 

could experience irritating 

effects to their eyes and 

nose. Some people who 

drink water containing 

chlorine well in excess of 

the MRDL could 

experience stomach 

discomfort.

85. Chloramines 4 (MRDLG) 4.0 

(MRDL)

Some people who use 

water containing 

chloramines well in excess 

of the MRDL could 

experience irritating effects 

to their eyes and nose. 

Some people who drink 

water containing 

chloramines well in excess 

of the MRDL could 

experience stomach 

discomfort or anemia.

86a. Chlorine dioxide, where 

any 2 consecutive daily 

samples taken at the 

entrance to the distribution 

system are above the MRDL

0.8 

(MRDLG)

0.8 

(MRDL)

Some infants and young 

children who drink water 

containing chlorine dioxide 

in excess of the MRDL 

could experience nervous 

system effects. Similar 

effects may occur in 

fetuses of pregnant women 

who drink water containing 

chlorine dioxide in excess 

of the MRDL. Some people 

may experience anemia.

 Add for public notification 

only: The chlorine dioxide 

violations reported today 

are the result of 

exceedances at the 

treatment facility only, not 

within the distribution 

system which delivers 

water to consumers. 

Continued compliance with 

chlorine dioxide levels 

within the distribution 

system minimizes the 

potential risk of these 

violations to consumers.

86b. Chlorine dioxide, where 

one or more distribution 

system samples are above 

the MRDL

0.8 

(MRDLG)

0.8 

(MRDL)

Some infants and young 

children who drink water 

containing chlorine dioxide 

in excess of the MRDL 

could experience nervous 

system effects. Similar 

effects may occur in 

fetuses of pregnant women 

who drink water containing 

chlorine dioxide in excess 

of the MRDL. Some people 

may experience anemia.

 Add for public notification 

only: The chlorine dioxide 

violations reported today 

include exceedances of the 

EPA standard within the 

distribution system which 

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Appendix B—Endnotes 

1. MCLG—Maximum contaminant level goal 

2. MCL—Maximum contaminant level 

3. For water systems analyzing at least 40 samples per month, no more than 5.0 percent of the monthly 

samples may be positive for total coliforms. For systems analyzing fewer than 40 samples per month, no 

more than one sample per month may be positive for total coliforms. 

4. There are various regulations that set turbidity standards for different types of systems, including 40 

CFR 141.13, and the 1989 Surface Water Treatment Rule, the 1998 Interim Enhanced Surface Water 

Treatment Rule and the 2002 Long Term 1 Enhanced Surface Water Treatment Rule. The MCL for the 

monthly turbidity average is 1 NTU; the MCL for the 2-day average is 5 NTU for systems that are 

required to filter but have not yet installed filtration (40 CFR 141.13). 

5. NTU—Nephelometric turbidity unit 

6. There are various regulations that set turbidity standards for different types of systems, including 40 

CFR 141.13, and the 1989 Surface Water Treatment Rule, the 1998 Interim Enhanced Surface Water 

Treatment Rule and the 2001 Long Term 1 Enhanced Surface Water Treatment Rule. Systems subject 

to the Surface Water Treatment Rule (both filtered and unfiltered) may not exceed 5 NTU. In addition, in 

filtered systems, 95 percent of samples each month must not exceed 0.5 NTU in systems using 

conventional or direct filtration and must not exceed 1 NTU in systems using slow sand or diatomaceous 

earth filtration or other filtration technologies approved by the primacy agency. 

7. TT—Treatment technique 

delivers water to 

consumers. Violations of 

the chlorine dioxide 

standard within the 

distribution system may 

harm human health based 

on short-term exposures. 

Certain groups, including 

fetuses, infants, and young 

children, may be especially 

susceptible to nervous 

system effects from 

excessive chlorine dioxide 

exposure.

87. Control of DBP precursors 

(TOC)

None TT Total organic carbon 

(TOC) has no health 

effects. However, total 

organic carbon provides a 

medium for the formation 

of disinfection byproducts. 

These byproducts include 

trihalomethanes (THMs) 

and haloacetic acids 

(HAAs). Drinking water 

containing these 

byproducts in excess of the 

MCL may lead to adverse 

health effects, liver or 

kidney problems, or 

nervous system effects, 

and may lead to an 

increased risk of getting 

cancer.

I. Other Treatment Techniques

88. Acrylamide Zero TT Some people who drink 

water containing high 

levels of acrylamide over a 

long period of time could 

have problems with their 

nervous system or blood, 

and may have an 

increased risk of getting 

cancer.

89. Epichlorohydrin Zero TT Some people who drink 

water containing high 

levels of epichlorohydrin 

over a long period of time 

could experience stomach 

problems, and may have 

an increased risk of getting 

cancer.

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8. There are various regulations that set turbidity standards for different types of systems, including 40 

CFR 141.13, the 1989 Surface Water Treatment Rule (SWTR), the 1998 Interim Enhanced Surface 

Water Treatment Rule (IESWTR) and the 2002 Long Term 1 Enhanced Surface Water Treatment Rule 

(LT1ESWTR). For systems subject to the IESWTR (systems serving at least 10,000 people, using 

surface water or ground water under the direct influence of surface water), that use conventional 

filtration or direct filtration, after January 1, 2002, the turbidity level of a system's combined filter effluent 

may not exceed 0.3 NTU in at least 95 percent of monthly measurements, and the turbidity level of a 

system's combined filter effluent must not exceed 1 NTU at any time. Systems subject to the IESWTR 

using technologies other than conventional, direct, slow sand, or diatomaceous earth filtration must meet 

turbidity limits set by the primacy agency. For systems subject to the LT1ESWTR (systems serving 

fewer than 10,000 people, using surface water or ground water under the direct influence of surface 

water) that use conventional filtration or direct filtration, after January 1, 2005, the turbidity level of a 

system's combined filter effluent may not exceed 0.3 NTU in at least 95 percent of monthly 

measurements, and the turbidity level of a system's combined filter effluent must not exceed 1 NTU at 

any time. Systems subject to the LT1ESWTR using technologies other than conventional, direct, slow 

sand, or diatomaceous earth filtration must meet turbidity limits set by the primacy agency. 

9. The bacteria detected by heterotrophic plate count (HPC) are not necessarily harmful. HPC is simply 

an alternative method of determining disinfectant residual levels. The number of such bacteria is an 

indicator of whether there is enough disinfectant in the distribution system. 

10. SWTR, IESWTR, and LT1ESWTR treatment technique violations that involve turbidity exceedances 

may use the health effects language for turbidity instead. 

11. These arsenic values are effective January 23, 2006. Until then, the MCL is 0.05 mg/L and there is 

no MCLG. 

12. Millions fibers per liter. 

13. Action Level = 0.015 mg/L 

14. Action Level = 1.3 mg/L 

15. Millirems per years 

16. The uranium MCL is effective December 8, 2003 for all community water systems. 

17. Picocuries per liter 

18. Surface water systems and ground water systems under the direct influence of surface water are 

regulated under subpart H of 40 CFR 141. Subpart H community and non-transient non-community 

systems serving ≥10,000 must comply with subpart L DBP MCLs and disinfectant maximum residual 

disinfectant levels (MRDLs) beginning January 1, 2002. All other community and non-transient noncommunity systems must comply with subpart L DBP MCLs and disinfectant MRDLs beginning January 

1, 2004. Subpart H transient non-community systems serving ≥10,000 that use chlorine dioxide as a 

disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning January 1, 2002. All other 

transient non-community systems that use chlorine dioxide as a disinfectant or oxidant must comply with 

the chlorine dioxide MRDL beginning January 1, 2004. 

19. Community and non-transient non-community systems must comply with subpart V TTHM and HAA5 

MCLs of 0.080 mg/L and 0.060 mg/L, respectively (with compliance calculated as a locational running 

annual average) on the schedule in §141.620. 

20. The MCL for total trihalomethanes is the sum of the concentrations of the individual trihalomethanes. 

21. The MCL for haloacetic acids is the sum of the concentrations of the individual haloacetic acids. 

22. MRDLG—Maximum residual disinfectant level goal. 

23. MRDL—Maximum residual disinfectant level. 

[65 FR 26043, May 4, 2000; 65 FR 38629, June 21, 2000; 65 FR 40521, 40522, June 30, 2000, as 

amended at 65 FR 76751, Dec. 7, 2000; 66 FR 7065, Jan. 22, 2001; 66 FR 31104, June 8, 2001; 67 FR 

1838, Jan. 14, 2002; 67 FR 70857, Nov. 27, 2002; 68 FR 14507, Mar. 25, 2003; 69 FR 38856, June 29, 

2004; 71 FR 483, Jan. 4, 2006; 71 FR 65653, Nov. 8, 2006] 

Appendix C to Subpart Q of Part 141—List of Acronyms Used in Public Notification 

Regulation 

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CCR Consumer Confidence Report 

CWS Community Water System 

DBP Disinfection Byproduct 

EPA Environmental Protection Agency 

GWR Ground Water Rule 

HPC Heterotrophic Plate Count 

IESWTR Interim Enhanced Surface Water Treatment Rule 

IOC Inorganic Chemical 

LCR Lead and Copper Rule 

MCL Maximum Contaminant Level 

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MCLG Maximum Contaminant Level Goal 

MRDL Maximum Residual Disinfectant Level 

MRDLG Maximum Residual Disinfectant Level Goal 

NCWS Non-Community Water System 

NPDWR National Primary Drinking Water Regulation 

NTNCWS Non-Transient Non-Community Water System 

NTU Nephelometric Turbidity Unit 

OGWDW Office of Ground Water and Drinking Water 

OW Office of Water 

PN Public Notification 

PWS Public Water System 

SDWA Safe Drinking Water Act 

SMCL Secondary Maximum Contaminant Level 

SOC Synthetic Organic Chemical 

SWTR Surface Water Treatment Rule 

TCR Total Coliform Rule 

TT Treatment Technique 

TWS Transient Non-Community Water System 

VOC Volatile Organic Chemical 

[65 FR 26035, May 4, 2000, as amended at 71 FR 65653, Nov. 8, 2006] 

Subpart R [Reserved] 

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Subpart S—Ground Water Rule 

 top

Source: 71 FR 65653, Nov. 8, 2006, unless otherwise noted. 

§ 141.400 General requirements and applicability. 

 top

(a) Scope of this subpart. The requirements of this subpart S constitute National Primary Drinking Water 

Regulations. 

(b) Applicability. This subpart applies to all public water systems that use ground water except that it 

does not apply to public water systems that combine all of their ground water with surface water or with 

ground water under the direct influence of surface water prior to treatment under subpart H. For the 

purposes of this subpart, “ground water system” is defined as any public water system meeting this 

applicability statement, including consecutive systems receiving finished ground water. 

(c) General requirements. Systems subject to this subpart must comply with the following requirements: 

(1) Sanitary survey information requirements for all ground water systems as described in §141.401. 

(2) Microbial source water monitoring requirements for ground water systems that do not treat all of their 

ground water to at least 99.99 percent (4-log) treatment of viruses (using inactivation, removal, or a 

State-approved combination of 4-log virus inactivation and removal) before or at the first customer as 

described in §141.402. 

(3) Treatment technique requirements, described in §141.403, that apply to ground water systems that 

have fecally contaminated source waters, as determined by source water monitoring conducted under 

§141.402, or that have significant deficiencies that are identified by the State or that are identified by 

EPA under SDWA section 1445. A ground water system with fecally contaminated source water or with 

significant deficiencies subject to the treatment technique requirements of this subpart must implement 

one or more of the following corrective action options: correct all significant deficiencies; provide an 

alternate source of water; eliminate the source of contamination; or provide treatment that reliably 

achieves at least 4-log treatment of viruses (using inactivation, removal, or a State-approved 

combination of 4-log virus inactivation and removal) before or at the first customer. 

(4) Ground water systems that provide at least 4-log treatment of viruses (using inactivation, removal, or 

a State-approved combination of 4-log virus inactivation and removal) before or at the first customer are 

required to conduct compliance monitoring to demonstrate treatment effectiveness, as described in 

§141.403(b). 

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(5) If requested by the State, ground water systems must provide the State with any existing information 

that will enable the State to perform a hydrogeologic sensitivity assessment. For the purposes of this 

subpart, “hydrogeologic sensitivity assessment” is a determination of whether ground water systems 

obtain water from hydrogeologically sensitive settings. 

(d) Compliance date. Ground water systems must comply, unless otherwise noted, with the 

requirements of this subpart beginning December 1, 2009. 

§ 141.401 Sanitary surveys for ground water systems. 

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(a) Ground water systems must provide the State, at the State's request, any existing information that 

will enable the State to conduct a sanitary survey. 

(b) For the purposes of this subpart, a “sanitary survey,” as conducted by the State, includes but is not 

limited to, an onsite review of the water source(s) (identifying sources of contamination by using results 

of source water assessments or other relevant information where available), facilities, equipment, 

operation, maintenance, and monitoring compliance of a public water system to evaluate the adequacy 

of the system, its sources and operations and the distribution of safe drinking water. 

(c) The sanitary survey must include an evaluation of the applicable components listed in paragraphs (c)

(1) through (8) of this section: 

(1) Source, 

(2) Treatment, 

(3) Distribution system, 

(4) Finished water storage, 

(5) Pumps, pump facilities, and controls, 

(6) Monitoring, reporting, and data verification, 

(7) System management and operation, and 

(8) Operator compliance with State requirements. 

§ 141.402 Ground water source microbial monitoring and analytical methods. 

 top

(a) Triggered source water monitoring —(1) General requirements. A ground water system must conduct 

triggered source water monitoring if the conditions identified in paragraphs (a)(1)(i) and (a)(1)(ii) of this 

section exist. 

(i) The system does not provide at least 4-log treatment of viruses (using inactivation, removal, or a 

State-approved combination of 4-log virus inactivation and removal) before or at the first customer for 

each ground water source; and 

(ii) The system is notified that a sample collected under §141.21(a) is total coliform-positive and the 

sample is not invalidated under §141.21(c). 

(2) Sampling requirements. A ground water system must collect, within 24 hours of notification of the 

total coliform-positive sample, at least one ground water source sample from each ground water source 

in use at the time the total coliform-positive sample was collected under §141.21(a), except as provided 

in paragraph (a)(2)(ii) of this section. 

(i) The State may extend the 24-hour time limit on a case-by-case basis if the system cannot collect the 

ground water source water sample within 24 hours due to circumstances beyond its control. In the case 

of an extension, the State must specify how much time the system has to collect the sample. 

(ii) If approved by the State, systems with more than one ground water source may meet the 

requirements of this paragraph (a)(2) by sampling a representative ground water source or sources. If 

directed by the State, systems must submit for State approval a triggered source water monitoring plan 

that identifies one or more ground water sources that are representative of each monitoring site in the 

system's sample siting plan under §141.21(a) and that the system intends to use for representative 

sampling under this paragraph. 

(iii) A ground water system serving 1,000 people or fewer may use a repeat sample collected from a 

ground water source to meet both the requirements of §141.21(b) and to satisfy the monitoring 

requirements of paragraph (a)(2) of this section for that ground water source only if the State approves 

the use of E. coli as a fecal indicator for source water monitoring under this paragraph (a). If the repeat 

sample collected from the ground water source is E.coli positive, the system must comply with 

paragraph (a)(3) of this section. 

(3) Additional requirements. If the State does not require corrective action under §141.403(a)(2) for a 

fecal indicator-positive source water sample collected under paragraph (a)(2) of this section that is not 

invalidated under paragraph (d) of this section, the system must collect five additional source water 

samples from the same source within 24 hours of being notified of the fecal indicator-positive sample. 

(4) Consecutive and wholesale systems —(i) In addition to the other requirements of this paragraph (a), 

a consecutive ground water system that has a total coliform-positive sample collected under §141.21(a) 

must notify the wholesale system(s) within 24 hours of being notified of the total coliform-positive 

sample. 

(ii) In addition to the other requirements of this paragraph (a), a wholesale ground water system must 

comply with paragraphs (a)(4)(ii)(A) and (a)(4)(ii)(B) of this section. 

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(A) A wholesale ground water system that receives notice from a consecutive system it serves that a 

sample collected under §141.21(a) is total coliform-positive must, within 24 hours of being notified, 

collect a sample from its ground water source(s) under paragraph (a)(2) of this section and analyze it for 

a fecal indicator under paragraph (c) of this section. 

(B) If the sample collected under paragraph (a)(4)(ii)(A) of this section is fecal indicator-positive, the 

wholesale ground water system must notify all consecutive systems served by that ground water source 

of the fecal indicator source water positive within 24 hours of being notified of the ground water source 

sample monitoring result and must meet the requirements of paragraph (a)(3) of this section. 

(5) Exceptions to the triggered source water monitoring requirements. A ground water system is not 

required to comply with the source water monitoring requirements of paragraph (a) of this section if 

either of the following conditions exists: 

(i) The State determines, and documents in writing, that the total coliform-positive sample collected 

under §141.21(a) is caused by a distribution system deficiency; or 

(ii) The total coliform-positive sample collected under §141.21(a) is collected at a location that meets 

State criteria for distribution system conditions that will cause total coliform-positive samples. 

(b) Assessment source water monitoring. If directed by the State, ground water systems must conduct 

assessment source water monitoring that meets State-determined requirements for such monitoring. A 

ground water system conducting assessment source water monitoring may use a triggered source water 

sample collected under paragraph (a)(2) of this section to meet the requirements of paragraph (b) of this 

section. State-determined assessment source water monitoring requirements may include: 

(1) Collection of a total of 12 ground water source samples that represent each month the system 

provides ground water to the public, 

(2) Collection of samples from each well unless the system obtains written State approval to conduct 

monitoring at one or more wells within the ground water system that are representative of multiple wells 

used by that system and that draw water from the same hydrogeologic setting, 

(3) Collection of a standard sample volume of at least 100 mL for fecal indicator analysis regardless of 

the fecal indicator or analytical method used, 

(4) Analysis of all ground water source samples using one of the analytical methods listed in the in 

paragraph (c)(2) of this section for the presence of E. coli , enterococci, or coliphage, 

(5) Collection of ground water source samples at a location prior to any treatment of the ground water 

source unless the State approves a sampling location after treatment, and 

(6) Collection of ground water source samples at the well itself unless the system's configuration does 

not allow for sampling at the well itself and the State approves an alternate sampling location that is 

representative of the water quality of that well. 

(c) Analytical methods. (1) A ground water system subject to the source water monitoring requirements 

of paragraph (a) of this section must collect a standard sample volume of at least 100 mL for fecal 

indicator analysis regardless of the fecal indicator or analytical method used. 

(2) A ground water system must analyze all ground water source samples collected under paragraph (a) 

of this section using one of the analytical methods listed in the following table in paragraph (c)(2) of this 

section or one of the alternative methods listed in appendix A to subpart C of this part for the presence 

of E. coli , enterococci, or coliphage: 

Analytical Methods for Source Water Monitoring 

Analyses must be conducted in accordance with the documents listed below. The Director of the Federal 

Register approves the incorporation by reference of the documents listed in footnotes 2–11 in 

accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the documents may be obtained from the 

sources listed below. Copies may be inspected at EPA's Drinking Water Docket, EPA West, 1301 

Fecal 

indicator1 Methodology Method citation

E. coli Colilert3 9223 B.2

 Colisure3 9223 B.2

 Membrane Filter Method with MI Agar EPA Method 

1604.4

 m-ColiBlue24 Test5

 E*Colite Test6

 EC–MUG7 9221 F.2

 NA–MUG7 9222 G.2

Enterococci Multiple-Tube Technique 9230B.2

 Membrane Filter Technique 9230C.2

 Membrane Filter Technique EPA Method 

1600.8

 Enterolert9

Coliphage Two-Step Enrichment Presence-Absence 

Procedure

EPA Method 

1601.10

 Single Agar Layer Procedure EPA Method 

1602.11

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Constitution Avenue, NW., EPA West, Room B102, Washington DC 20460 (Telephone: 202–566–2426); 

or at the National Archives and Records Administration (NARA). For information on the availability of this 

material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. 

1The time from sample collection to initiation of analysis may not exceed 30 hours. The ground water 

system is encouraged but is not required to hold samples below 10 °C during transit. 

2Methods are described in Standard Methods for the Examination of Water and Wastewater 20th edition 

(1998) and copies may be obtained from the American Public Health Association, 1015 Fifteenth Street, 

NW., Washington, DC 20005–2605. 

3Medium is available through IDEXX Laboratories, Inc., One IDEXX Drive, Westbrook, Maine 04092.

4EPA Method 1604: Total Coliforms and Escherichia coli in Water by Membrane Filtration Using a 

Simultaneous Detection Technique (MI Medium); September 2002, EPA 821–R–02–024. Method is 

available at http://www.epa.gov/nerlcwww/1604sp02.pdf or from EPA's Water Resource Center (RC–

4100T), 1200 Pennsylvania Avenue, NW., Washington, DC 20460. 

5A description of the m-ColiBlue24 Test, “Total Coliforms and E. coli Membrane Filtration Method with 

m-ColiBlue24®Broth,” Method No. 10029 Revision 2, August 17, 1999, is available from Hach Company, 

100 Dayton Ave., Ames, IA 50010 or from EPA's Water Resource Center (RC–4100T), 1200 

Pennsylvania Avenue, NW., Washington, DC 20460. 

6A description of the E*Colite Test, “Charm E*Colite Presence/Absence Test for Detection and 

Identification of Coliform Bacteria and Escherichia coli in Drinking Water, January 9, 1998, is available 

from Charm Sciences, Inc., 659 Andover St., Lawrence, MA 01843–1032 or from EPA's Water Resource 

Center (RC–4100T), 1200 Pennsylvania Avenue, NW., Washington, DC 20460. 

7EC–MUG (Method 9221F) or NA–MUG (Method 9222G) can be used for E. coli testing step as 

described in §141.21(f)(6)(i) or (ii) after use of Standard Methods 9221 B, 9221 D, 9222 B, or 9222 C. 

8EPA Method 1600: Enterococci in Water by Membrane Filtration Using membrane-Enterococcus 

Indoxyl–β–D–Glucoside Agar (mEI) EPA 821–R–02–022 (September 2002) is an approved variation of 

Standard Method 9230C. The method is available at http://www.epa.gov/nerlcwww/1600sp02.pdf or 

from EPA's Water Resource Center (RC–4100T), 1200 Pennsylvania Avenue, NW., Washington, DC 

20460. The holding time and temperature for ground water samples are specified in footnote 1 above, 

rather than as specified in Section 8 of EPA Method 1600. 

9Medium is available through IDEXX Laboratories, Inc., One IDEXX Drive, Westbrook, Maine 04092. 

Preparation and use of the medium is set forth in the article “Evaluation of Enterolert for Enumeration of 

Enterococci in Recreational Waters,” by Budnick, G.E., Howard, R.T., and Mayo, D.R., 1996, Applied 

and Environmental Microbiology, 62:3881–3884. 

10EPA Method 1601: Male-specific (F+) and Somatic Coliphage in Water by Two-step Enrichment 

Procedure; April 2001, EPA 821–R–01–030. Method is available at 

http://www.epa.gov/nerlcwww/1601ap01.pdf or from EPA's Water Resource Center (RC–4100T), 1200 

Pennsylvania Avenue, NW., Washington, DC 20460. 

11EPA Method 1602: Male-specific (F+) and Somatic Coliphage in Water by Single Agar Layer (SAL) 

Procedure; April 2001, EPA 821–R–01–029. Method is available at 

http://www.epa.gov/nerlcwww/1602ap01.pdf or from EPA's Water Resource Center (RC–4100T), 1200 

Pennsylvania Avenue, NW., Washington, DC 20460. 

(d) Invalidation of a fecal indicator-positive ground water source sample . (1) A ground water system 

may obtain State invalidation of a fecal indicator-positive ground water source sample collected under 

paragraph (a) of this section only under the conditions specified in paragraphs (d)(1)(i) and (ii) of this 

section. 

(i) The system provides the State with written notice from the laboratory that improper sample analysis 

occurred; or 

(ii) The State determines and documents in writing that there is substantial evidence that a fecal 

indicator-positive ground water source sample is not related to source water quality. 

(2) If the State invalidates a fecal indicator-positive ground water source sample, the ground water 

system must collect another source water sample under paragraph (a) of this section within 24 hours of 

being notified by the State of its invalidation decision and have it analyzed for the same fecal indicator 

using the analytical methods in paragraph (c) of this section. The State may extend the 24-hour time 

limit on a case-by-case basis if the system cannot collect the source water sample within 24 hours due 

to circumstances beyond its control. In the case of an extension, the State must specify how much time 

the system has to collect the sample. 

(e) Sampling location. (1) Any ground water source sample required under paragraph (a) of this section 

must be collected at a location prior to any treatment of the ground water source unless the State 

approves a sampling location after treatment. 

(2) If the system's configuration does not allow for sampling at the well itself, the system may collect a 

sample at a State-approved location to meet the requirements of paragraph (a) of this section if the 

sample is representative of the water quality of that well. 

(f) New sources. If directed by the State, a ground water system that places a new ground water source 

into service after November 30, 2009, must conduct assessment source water monitoring under 

paragraph (b) of this section. If directed by the State, the system must begin monitoring before the 

ground water source is used to provide water to the public. 

(g) Public notification. A ground water system with a ground water source sample collected under 

paragraph (a) or (b) of this section that is fecal indicator-positive and that is not invalidated under 

paragraph (d) of this section, including consecutive systems served by the ground water source, must 

conduct public notification under §141.202. 

(h) Monitoring violations. Failure to meet the requirements of paragraphs (a)–(f) of this section is a 

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monitoring violation and requires the ground water system to provide public notification under §141.204. 

[71 FR 65653, Nov. 8, 2006; 71 FR 67427, Nov. 21, 2006, as amended at 74 FR 30958, June 29, 2009] 

§ 141.403 Treatment technique requirements for ground water systems. 

 top

(a) Ground water systems with significant deficiencies or source water fecal contamination. (1) The 

treatment technique requirements of this section must be met by ground water systems when a 

significant deficiency is identified or when a ground water source sample collected under §141.402(a)(3) 

is fecal indicator-positive. 

(2) If directed by the State, a ground water system with a ground water source sample collected under 

§141.402(a)(2), §141.402(a)(4), or §141.402(b) that is fecal indicator-positive must comply with the 

treatment technique requirements of this section. 

(3) When a significant deficiency is identified at a Subpart H public water system that uses both ground 

water and surface water or ground water under the direct influence of surface water, the system must 

comply with provisions of this paragraph except in cases where the State determines that the significant 

deficiency is in a portion of the distribution system that is served solely by surface water or ground water 

under the direct influence of surface water. 

(4) Unless the State directs the ground water system to implement a specific corrective action, the 

ground water system must consult with the State regarding the appropriate corrective action within 30 

days of receiving written notice from the State of a significant deficiency, written notice from a laboratory 

that a ground water source sample collected under §141.402(a)(3) was found to be fecal indicatorpositive, or direction from the State that a fecal indicator'positive collected under §141.402(a)(2), 

§141.402(a)(4), or §141.402(b) requires corrective action. For the purposes of this subpart, significant 

deficiencies include, but are not limited to, defects in design, operation, or maintenance, or a failure or 

malfunction of the sources, treatment, storage, or distribution system that the State determines to be 

causing, or have potential for causing, the introduction of contamination into the water delivered to 

consumers. 

(5) Within 120 days (or earlier if directed by the State) of receiving written notification from the State of a 

significant deficiency, written notice from a laboratory that a ground water source sample collected under 

§141.402(a)(3) was found to be fecal indicator-positive, or direction from the State that a fecal indicatorpositive sample collected under §141.402(a)(2), §141.402(a)(4), or §141.402(b) requires corrective 

action, the ground water system must either: 

(i) Have completed corrective action in accordance with applicable State plan review processes or other 

State guidance or direction, if any, including State-specified interim measures; or 

(ii) Be in compliance with a State-approved corrective action plan and schedule subject to the conditions 

specified in paragraphs (a)(5)(ii)(A) and (a)(5)(ii)(B) of this section. 

(A) Any subsequent modifications to a State-approved corrective action plan and schedule must also be 

approved by the State. 

(B) If the State specifies interim measures for protection of the public health pending State approval of 

the corrective action plan and schedule or pending completion of the corrective action plan, the system 

must comply with these interim measures as well as with any schedule specified by the State. 

(6) Corrective action alternatives. Ground water systems that meet the conditions of paragraph (a)(1) or 

(a)(2) of this section must implement one or more of the following corrective action alternatives: 

(i) Correct all significant deficiencies; 

(ii) Provide an alternate source of water; 

(iii) Eliminate the source of contamination; or 

(iv) Provide treatment that reliably achieves at least 4-log treatment of viruses (using inactivation, 

removal, or a State-approved combination of 4-log virus inactivation and removal) before or at the first 

customer for the ground water source. 

(7) Special notice to the public of significant deficiencies or source water fecal contamination. (i) In 

addition to the applicable public notification requirements of §141.202, a community ground water 

system that receives notice from the State of a significant deficiency or notification of a fecal indicatorpositive ground water source sample that is not invalidated by the State under §141.402(d) must inform 

the public served by the water system under §141.153(h)(6) of the fecal indicator-positive source sample 

or of any significant deficiency that has not been corrected. The system must continue to inform the 

public annually until the significant deficiency is corrected or the fecal contamination in the ground water 

source is determined by the State to be corrected under paragraph (a)(5) of this section. 

(ii) In addition to the applicable public notification requirements of §141.202, a non-community ground 

water system that receives notice from the State of a significant deficiency must inform the public served 

by the water system in a manner approved by the State of any significant deficiency that has not been 

corrected within 12 months of being notified by the State, or earlier if directed by the State. The system 

must continue to inform the public annually until the significant deficiency is corrected. The information 

must include: 

(A) The nature of the significant deficiency and the date the significant deficiency was identified by the 

State; 

(B) The State-approved plan and schedule for correction of the significant deficiency, including interim 

measures, progress to date, and any interim measures completed; and 

(C) For systems with a large proportion of non-English speaking consumers, as determined by the State, 

information in the appropriate language(s) regarding the importance of the notice or a telephone number 

or address where consumers may contact the system to obtain a translated copy of the notice or 

assistance in the appropriate language. 

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(iii) If directed by the State, a non-community water system with significant deficiencies that have been 

corrected must inform its customers of the significant deficiencies, how the deficiencies were corrected, 

and the dates of correction under paragraph (a)(7)(ii) of this section. 

(b) Compliance monitoring —(1) Existing ground water sources. A ground water system that is not 

required to meet the source water monitoring requirements of this subpart for any ground water source 

because it provides at least 4-log treatment of viruses (using inactivation, removal, or a State-approved 

combination of 4-log virus inactivation and removal) before or at the first customer for any ground water 

source before December 1, 2009, must notify the State in writing that it provides at least 4-log treatment 

of viruses (using inactivation, removal, or a State-approved combination of 4-log virus inactivation and 

removal) before or at the first customer for the specified ground water source and begin compliance 

monitoring in accordance with paragraph (b)(3) of this section by December 1, 2009. Notification to the 

State must include engineering, operational, or other information that the State requests to evaluate the 

submission. If the system subsequently discontinues 4-log treatment of viruses (using inactivation, 

removal, or a State-approved combination of 4-log virus inactivation and removal) before or at the first 

customer for a ground water source, the system must conduct ground water source monitoring as 

required under §141.402. 

(2) New ground water sources. A ground water system that places a ground water source in service 

after November 30, 2009, that is not required to meet the source water monitoring requirements of this 

subpart because the system provides at least 4-log treatment of viruses (using inactivation, removal, or 

a State-approved combination of 4-log virus inactivation and removal) before or at the first customer for 

the ground water source must comply with the requirements of paragraphs (b)(2)(i), (b)(2)(ii) and (b)(2)

(iii) of this section. 

(i) The system must notify the State in writing that it provides at least 4-log treatment of viruses (using 

inactivation, removal, or a State-approved combination of 4-log virus inactivation and removal) before or 

at the first customer for the ground water source. Notification to the State must include engineering, 

operational, or other information that the State requests to evaluate the submission. 

(ii) The system must conduct compliance monitoring as required under §141.403(b)(3) of this subpart 

within 30 days of placing the source in service. 

(iii) The system must conduct ground water source monitoring under §141.402 if the system 

subsequently discontinues 4-log treatment of viruses (using inactivation, removal, or a State-approved 

combination of 4-log virus inactivation and removal) before or at the first customer for the ground water 

source. 

(3) Monitoring requirements. A ground water system subject to the requirements of paragraphs (a), (b)

(1) or (b)(2) of this section must monitor the effectiveness and reliability of treatment for that ground 

water source before or at the first customer as follows: 

(i) Chemical disinfection —(A) Ground water systems serving greater than 3,300 people. A ground water 

system that serves greater than 3,300 people must continuously monitor the residual disinfectant 

concentration using analytical methods specified in §141.74(a)(2) at a location approved by the State 

and must record the lowest residual disinfectant concentration each day that water from the ground 

water source is served to the public. The ground water system must maintain the State-determined 

residual disinfectant concentration every day the ground water system serves water from the ground 

water source to the public. If there is a failure in the continuous monitoring equipment, the ground water 

system must conduct grab sampling every four hours until the continuous monitoring equipment is 

returned to service. The system must resume continuous residual disinfectant monitoring within 14 days. 

(B) Ground water systems serving 3,300 or fewer people. A ground water system that serves 3,300 or 

fewer people must monitor the residual disinfectant concentration using analytical methods specified in 

§141.74(a)(2) at a location approved by the State and record the residual disinfection concentration 

each day that water from the ground water source is served to the public. The ground water system 

must maintain the State-determined residual disinfectant concentration every day the ground water 

system serves water from the ground water source to the public. The ground water system must take a 

daily grab sample during the hour of peak flow or at another time specified by the State. If any daily grab 

sample measurement falls below the State-determined residual disinfectant concentration, the ground 

water system must take follow-up samples every four hours until the residual disinfectant concentration 

is restored to the State-determined level. Alternatively, a ground water system that serves 3,300 or fewer 

people may monitor continuously and meet the requirements of paragraph (b)(3)(i)(A) of this section. 

(ii) Membrane filtration. A ground water system that uses membrane filtration to meet the requirements 

of this subpart must monitor the membrane filtration process in accordance with all State-specified 

monitoring requirements and must operate the membrane filtration in accordance with all State-specified 

compliance requirements. A ground water system that uses membrane filtration is in compliance with the 

requirement to achieve at least 4-log removal of viruses when: 

(A) The membrane has an absolute molecular weight cut-off (MWCO), or an alternate parameter that 

describes the exclusion characteristics of the membrane, that can reliably achieve at least 4-log removal 

of viruses; 

(B) The membrane process is operated in accordance with State-specified compliance requirements; 

and 

(C) The integrity of the membrane is intact. 

(iii) Alternative treatment. A ground water system that uses a State-approved alternative treatment to 

meet the requirements of this subpart by providing at least 4-log treatment of viruses (using inactivation, 

removal, or a State-approved combination of 4-log virus inactivation and removal) before or at the first 

customer must: 

(A) Monitor the alternative treatment in accordance with all State-specified monitoring requirements; and 

(B) Operate the alternative treatment in accordance with all compliance requirements that the State 

determines to be necessary to achieve at least 4-log treatment of viruses. 

(c) Discontinuing treatment. A ground water system may discontinue 4-log treatment of viruses (using 

inactivation, removal, or a State-approved combination of 4-log virus inactivation and removal) before or 

at the first customer for a ground water source if the State determines and documents in writing that 4-

log treatment of viruses is no longer necessary for that ground water source. A system that discontinues 

4-log treatment of viruses is subject to the source water monitoring and analytical methods requirements 

of §141.402 of this subpart. 

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(d) Failure to meet the monitoring requirements of paragraph (b) of this section is a monitoring violation 

and requires the ground water system to provide public notification under §141.204. 

§ 141.404 Treatment technique violations for ground water systems. 

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(a) A ground water system with a significant deficiency is in violation of the treatment technique 

requirement if, within 120 days (or earlier if directed by the State) of receiving written notice from the 

State of the significant deficiency, the system: 

(1) Does not complete corrective action in accordance with any applicable State plan review processes 

or other State guidance and direction, including State specified interim actions and measures, or 

(2) Is not in compliance with a State-approved corrective action plan and schedule. 

(b) Unless the State invalidates a fecal indicator-positive ground water source sample under §141.402

(d), a ground water system is in violation of the treatment technique requirement if, within 120 days (or 

earlier if directed by the State) of meeting the conditions of §141.403(a)(1) or §141.403(a)(2), the 

system: 

(1) Does not complete corrective action in accordance with any applicable State plan review processes 

or other State guidance and direction, including State-specified interim measures, or 

(2) Is not in compliance with a State-approved corrective action plan and schedule. 

(c) A ground water system subject to the requirements of §141.403(b)(3) that fails to maintain at least 4-

log treatment of viruses (using inactivation, removal, or a State-approved combination of 4-log virus 

inactivation and removal) before or at the first customer for a ground water source is in violation of the 

treatment technique requirement if the failure is not corrected within four hours of determining the 

system is not maintaining at least 4-log treatment of viruses before or at the first customer. 

(d) Ground water system must give public notification under §141.203 for the treatment technique 

violations specified in paragraphs (a), (b) and (c) of this section. 

§ 141.405 Reporting and recordkeeping for ground water systems. 

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(a) Reporting. In addition to the requirements of §141.31, a ground water system regulated under this 

subpart must provide the following information to the State: 

(1) A ground water system conducting compliance monitoring under §141.403(b) must notify the State 

any time the system fails to meet any State-specified requirements including, but not limited to, minimum 

residual disinfectant concentration, membrane operating criteria or membrane integrity, and alternative 

treatment operating criteria, if operation in accordance with the criteria or requirements is not restored 

within four hours. The ground water system must notify the State as soon as possible, but in no case 

later than the end of the next business day. 

(2) After completing any corrective action under §141.403(a), a ground water system must notify the 

State within 30 days of completion of the corrective action. 

(3) If a ground water system subject to the requirements of §141.402(a) does not conduct source water 

monitoring under §141.402(a)(5)(ii), the system must provide documentation to the State within 30 days 

of the total coliform positive sample that it met the State criteria. 

(b) Recordkeeping. In addition to the requirements of §141.33, a ground water system regulated under 

this subpart must maintain the following information in its records: 

(1) Documentation of corrective actions. Documentation shall be kept for a period of not less than ten 

years. 

(2) Documentation of notice to the public as required under §141.403(a)(7). Documentation shall be kept 

for a period of not less than three years. 

(3) Records of decisions under §141.402(a)(5)(ii) and records of invalidation of fecal indicator-positive 

ground water source samples under §141.402(d). Documentation shall be kept for a period of not less 

than five years. 

(4) For consecutive systems, documentation of notification to the wholesale system(s) of total-coliform 

positive samples that are not invalidated under §141.21(c). Documentation shall be kept for a period of 

not less than five years. 

(5) For systems, including wholesale systems, that are required to perform compliance monitoring under 

§141.403(b): 

(i) Records of the State-specified minimum disinfectant residual. Documentation shall be kept for a 

period of not less than ten years. 

(ii) Records of the lowest daily residual disinfectant concentration and records of the date and duration of 

any failure to maintain the State-prescribed minimum residual disinfectant concentration for a period of 

more than four hours. Documentation shall be kept for a period of not less than five years. 

(iii) Records of State-specified compliance requirements for membrane filtration and of parameters 

specified by the State for State-approved alternative treatment and records of the date and duration of 

any failure to meet the membrane operating, membrane integrity, or alternative treatment operating 

requirements for more than four hours. Documentation shall be kept for a period of not less than five 

years. 

Subpart T—Enhanced Filtration and Disinfection—Systems Serving Fewer Than 10,000 

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People 

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Source: 67 FR 1839, Jan. 14, 2002, unless otherwise noted. 

General Requirements 

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§ 141.500 General requirements. 

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The requirements of this subpart constitute national primary drinking water regulations. These 

regulations establish requirements for filtration and disinfection that are in addition to criteria under which 

filtration and disinfection are required under subpart H of this part. The regulations in this subpart 

establish or extend treatment technique requirements in lieu of maximum contaminant levels for the 

following contaminants: Giardia lamblia, viruses, heterotrophic plate count bacteria, Legionella, 

Cryptosporidium and turbidity. The treatment technique requirements consist of installing and properly 

operating water treatment processes which reliably achieve: 

(a) At least 99 percent (2 log) removal of Cryptosporidium between a point where the raw water is not 

subject to recontamination by surface water runoff and a point downstream before or at the first 

customer for filtered systems, or Cryptosporidium control under the watershed control plan for unfiltered 

systems; and 

(b) Compliance with the profiling and benchmark requirements in §§141.530 through 141.544. 

§ 141.501 Who is subject to the requirements of subpart T? 

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You are subject to these requirements if your system: 

(a) Is a public water system; 

(b) Uses surface water or GWUDI as a source; and 

(c) Serves fewer than 10,000 persons. 

§ 141.502 When must my system comply with these requirements? 

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You must comply with these requirements in this subpart beginning January 1, 2005, except where 

otherwise noted. 

[69 FR 38856, June 29, 2004] 

§ 141.503 What does subpart T require? 

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There are seven requirements of this subpart, and you must comply with all requirements that are 

applicable to your system. These requirements are: 

(a) You must cover any finished water reservoir that you began to construct on or after March 15, 2002 

as described in §§141.510 and 141.511; 

(b) If your system is an unfiltered system, you must comply with the updated watershed control 

requirements described in §§141.520–141.522; 

(c) If your system is a community or non-transient non-community water systems you must develop a 

disinfection profile as described in §§141.530–141.536; 

(d) If your system is considering making a significant change to its disinfection practices, you must 

develop a disinfection benchmark and consult with the State for approval of the change as described in 

§§141.540–141.544; 

(e) If your system is a filtered system, you must comply with the combined filter effluent requirements as 

described in §§141.550–141.553; 

(f) If your system is a filtered system that uses conventional or direct filtration, you must comply with the 

individual filter turbidity requirements as described in §§141.560–141.564; and 

(g) You must comply with the applicable reporting and recordkeeping requirements as described in 

§§141.570 and 141.571. 

Finished Water Reservoirs 

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§ 141.510 Is my system subject to the new finished water reservoir requirements? 

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All subpart H systems which serve fewer than 10,000 are subject to this requirement. 

§ 141.511 What is required of new finished water reservoirs? 

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If your system begins construction of a finished water reservoir on or after March 15, 2002 the reservoir 

must be covered. Finished water reservoirs for which your system began construction prior to March 15, 

2002 are not subject to this requirement. 

Additional Watershed Control Requirements for Unfiltered Systems 

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§ 141.520 Is my system subject to the updated watershed control requirements? 

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If you are a subpart H system serving fewer than 10,000 persons which does not provide filtration, you 

must continue to comply with all of the filtration avoidance criteria in §141.71, as well as the additional 

watershed control requirements in §141.521. 

§ 141.521 What updated watershed control requirements must my unfiltered system 

implement to continue to avoid filtration? 

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Your system must take any additional steps necessary to minimize the potential for contamination by 

Cryptosporidium oocysts in the source water. Your system's watershed control program must, for 

Cryptosporidium : 

(a) Identify watershed characteristics and activities which may have an adverse effect on source water 

quality; and 

(b) Monitor the occurrence of activities which may have an adverse effect on source water quality. 

§ 141.522 How does the State determine whether my system's watershed control 

requirements are adequate? 

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During an onsite inspection conducted under the provisions of §141.71(b)(3), the State must determine 

whether your watershed control program is adequate to limit potential contamination by Cryptosporidium 

oocysts. The adequacy of the program must be based on the comprehensiveness of the watershed 

review; the effectiveness of your program to monitor and control detrimental activities occurring in the 

watershed; and the extent to which your system has maximized land ownership and/or controlled land 

use within the watershed. 

Disinfection Profile 

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§ 141.530 What is a disinfection profile and who must develop one? 

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A disinfection profile is a graphical representation of your system's level of Giardia lamblia or virus 

inactivation measured during the course of a year. If you are a subpart H community or non-transient 

non-community water system which serves fewer than 10,000 persons, your system must develop a 

disinfection profile unless your State determines that your system's profile is unnecessary. Your State 

may approve the use of a more representative data set for disinfection profiling than the data set 

required under §§141.532–141.536. 

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004] 

§ 141.531 What criteria must a State use to determine that a profile is unnecessary? 

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States may only determine that a system's profile is unnecessary if a system's TTHM and HAA5 levels 

are below 0.064 mg/L and 0.048 mg/L, respectively. To determine these levels, TTHM and HAA5 

samples must be collected after January 1, 1998, during the month with the warmest water temperature, 

and at the point of maximum residence time in your distribution system. Your State may approve a more 

representative TTHM and HAA5 data set to determine these levels. 

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004] 

§ 141.532 How does my system develop a disinfection profile and when must it begin? 

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A disinfection profile consists of three steps: 

(a) First, your system must collect data for several parameters from the plant as discussed in §141.533 

over the course of 12 months. If your system serves between 500 and 9,999 persons you must begin to 

collect data no later than July 1, 2003. If your system serves fewer than 500 persons you must begin to 

collect data no later than January 1, 2004. 

(b) Second, your system must use this data to calculate weekly log inactivation as discussed in 

§§141.534 and 141.535; and 

(c) Third, your system must use these weekly log inactivations to develop a disinfection profile as 

specified in §141.536. 

§ 141.533 What data must my system collect to calculate a disinfection profile? 

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Your system must monitor the following parameters to determine the total log inactivation using the 

analytical methods in §141.74 (a), once per week on the same calendar day, over 12 consecutive 

months: 

(a) The temperature of the disinfected water at each residual disinfectant concentration sampling point 

during peak hourly flow; 

(b) If your system uses chlorine, the pH of the disinfected water at each residual disinfectant 

concentration sampling point during peak hourly flow; 

(c) The disinfectant contact time(s) (“T”) during peak hourly flow; and 

(d) The residual disinfectant concentration(s) (“C”) of the water before or at the first customer and prior 

to each additional point of disinfection during peak hourly flow. 

§ 141.534 How does my system use this data to calculate an inactivation ratio? 

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Use the tables in §141.74(b)(3)(v) to determine the appropriate CT99.9 value. Calculate the total 

inactivation ratio as follows, and multiply the value by 3.0 to determine log inactivation of Giardia lamblia: 

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004] 

§ 141.535 What if my system uses chloramines, ozone, or chlorine dioxide for primary 

disinfection? 

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If your system uses chloramines, ozone, or chlorine dioxide for primary disinfection, you must also 

calculate the logs of inactivation for viruses and develop an additional disinfection profile for viruses 

using methods approved by the State. 

§ 141.536 My system has developed an inactivation ratio; what must we do now? 

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Each log inactivation serves as a data point in your disinfection profile. Your system will have obtained 

52 measurements (one for every week of the year). This will allow your system and the State the 

opportunity to evaluate how microbial inactivation varied over the course of the year by looking at all 52 

measurements (your Disinfection Profile). Your system must retain the Disinfection Profile data in 

graphic form, such as a spreadsheet, which must be available for review by the State as part of a 

sanitary survey. Your system must use this data to calculate a benchmark if you are considering 

changes to disinfection practices. 

If your system 

 * * * Your system must determine * * *

(a) Uses only one 

point of 

disinfectant 

application

(1) One inactivation ratio (CTcalc/CT99.9) before or at the 

first customer during peak hourly flow 

 or

 (2) Successive CTcalc/CT99.9values, representing 

sequential inactivation ratios, between the point of 

disinfectant application and a point before or at the first 

customer during peak hourly flow. Under this alternative, 

your system must calculate the total inactivation ratio by 

determining (CTcalc/CT99.9) for each sequence and then 

adding the (CTcalc/CT99.9) values together to determine 

(ΣCTcalc/CT99.9).

(b) Uses more 

than one point of 

disinfectant 

application before 

the first customer

The (CTcalc/CT99.9) value of each disinfection segment 

immediately prior to the next point of disinfectant 

application, or for the final segment, before or at the first 

customer, during peak hourly flow using the procedure 

specified in paragraph (a)(2) of this section.

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Disinfection Benchmark 

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§ 141.540 Who has to develop a disinfection benchmark? 

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If you are a subpart H system required to develop a disinfection profile under §§141.530 through 

141.536, your system must develop a Disinfection Benchmark if you decide to make a significant change 

to your disinfection practice. Your system must consult with the State for approval before you can 

implement a significant disinfection practice change. 

§ 141.541 What are significant changes to disinfection practice? 

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Significant changes to disinfection practice include: 

(a) Changes to the point of disinfection; 

(b) Changes to the disinfectant(s) used in the treatment plant; 

(c) Changes to the disinfection process; or 

(d) Any other modification identified by the State. 

§ 141.542 What must my system do if we are considering a significant change to 

disinfection practices? 

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If your system is considering a significant change to its disinfection practice, your system must calculate 

a disinfection benchmark(s) as described in §§141.543 and 141.544 and provide the benchmark(s) to 

your State. Your system may only make a significant disinfection practice change after consulting with 

the State for approval. Your system must submit the following information to the State as part of the 

consultation and approval process: 

(a) A description of the proposed change; 

(b) The disinfection profile for Giardia lamblia (and, if necessary, viruses) and disinfection benchmark; 

(c) An analysis of how the proposed change will affect the current levels of disinfection; and 

(d) Any additional information requested by the State. 

§ 141.543 How is the disinfection benchmark calculated? 

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If your system is making a significant change to its disinfection practice, it must calculate a disinfection 

benchmark using the procedure specified in the following table. 

§ 141.544 What if my system uses chloramines, ozone, or chlorine dioxide for primary 

disinfection? 

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If your system uses chloramines, ozone or chlorine dioxide for primary disinfection your system must 

calculate the disinfection benchmark from the data your system collected for viruses to develop the 

disinfection profile in addition to the Giardia lamblia disinfection benchmark calculated under §141.543. 

This viral benchmark must be calculated in the same manner used to calculate the Giardia lamblia 

disinfection benchmark in §141.543. 

Combined Filter Effluent Requirements 

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§ 141.550 Is my system required to meet subpart T combined filter effluent turbidity 

limits? 

To calculate a disinfection benchmark your system must perform the 

following steps

Step 1: Using the data your system collected to develop the Disinfection 

Profile, determine the average Giardia lamblia inactivation for each calendar 

month by dividing the sum of all Giardia lamblia inactivations for that month 

by the number of values calculated for that month.

Step 2: Determine the lowest monthly average value out of the twelve values. 

This value becomes the disinfection benchmark.

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All subpart H systems which serve populations fewer than 10,000, are required to filter, and utilize 

filtration other than slow sand filtration or diatomaceous earth filtration must meet the combined filter 

effluent turbidity requirements of §§141.551–141.553 . If your system uses slow sand or diatomaceous 

earth filtration you are not required to meet the combined filter effluent turbidity limits of subpart T, but 

you must continue to meet the combined filter effluent turbidity limits in §141.73. 

§ 141.551 What strengthened combined filter effluent turbidity limits must my system 

meet? 

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Your system must meet two strengthened combined filter effluent turbidity limits. 

(a) The first combined filter effluent turbidity limit is a “95th percentile” turbidity limit that your system 

must meet in at least 95 percent of the turbidity measurements taken each month. Measurements must 

continue to be taken as described in §141.74(a) and (c). Monthly reporting must be completed according 

to §141.570. The following table describes the required limits for specific filtration technologies. 

(b) The second combined filter effluent turbidity limit is a “maximum” turbidity limit which your system 

may at no time exceed during the month. Measurements must continue to be taken as described in 

§141.74(a) and (c). Monthly reporting must be completed according to §141.570. The following table 

describes the required limits for specific filtration technologies. 

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004] 

§ 141.552 My system consists of “alternative filtration” and is required to conduct a 

demonstration—what is required of my system and how does the State establish my 

turbidity limits? 

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(a) If your system consists of alternative filtration(filtration other than slow sand filtration, diatomaceous 

earth filtration, conventional filtration, or direct filtration) you are required to conduct a demonstration 

(see tables in §141.551). Your system must demonstrate to the State, using pilot plant studies or other 

means, that your system's filtration, in combination with disinfection treatment, consistently achieves: 

(1) 99 percent removal of Cryptosporidium oocysts; 

(2) 99.9 percent removal and/or inactivation of Giardia lamblia cysts; and 

(3) 99.99 percent removal and/or inactivation of viruses. 

(b) [Reserved] 

§ 141.553 My system practices lime softening—is there any special provision 

regarding my combined filter effluent? 

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If your system practices lime softening, you may acidify representative combined filter effluent turbidity 

samples prior to analysis using a protocol approved by the State. 

Individual Filter Turbidity Requirements 

 top

§ 141.560 Is my system subject to individual filter turbidity requirements? 

 top

If your system consists 

of * * * Your 95th percentile turbidity value is * * *

(1) Conventional 

Filtration or Direct 

Filtration

0.3 NTU.

(2) All other “Alternative” 

Filtration

A value determined by the State (not to exceed 1 

NTU) based on the demonstration described in 

§141.552.

If your system consists 

of * * * Your maximum turbidity value is * * *

(1) Conventional 

Filtration or Direct 

Filtration

1 NTU.

(2) All other “Alternative 

Filtration”

A value determined by the State (not to exceed 5 

NTU) based on the demonstration as described in 

§141.552.

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If your system is a subpart H system serving fewer than 10,000 people and utilizing conventional 

filtration or direct filtration, you must conduct continuous monitoring of turbidity for each individual filter at 

your system. The following requirements apply to continuous turbidity monitoring: 

(a) Monitoring must be conducted using an approved method in §141.74(a); 

(b) Calibration of turbidimeters must be conducted using procedures specified by the manufacturer; 

(c) Results of turbidity monitoring must be recorded at least every 15 minutes; 

(d) Monthly reporting must be completed according to §141.570; and 

(e) Records must be maintained according to §141.571. 

§ 141.561 What happens if my system's turbidity monitoring equipment fails? 

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If there is a failure in the continuous turbidity monitoring equipment, your system must conduct grab 

sampling every four hours in lieu of continuous monitoring until the turbidimeter is back on-line. Your 

system has 14 days to resume continuous monitoring before a violation is incurred. 

§ 141.562 My system only has two or fewer filters—is there any special provision 

regarding individual filter turbidity monitoring? 

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Yes, if your system only consists of two or fewer filters, you may conduct continuous monitoring of 

combined filter effluent turbidity in lieu of individual filter effluent turbidity monitoring. Continuous 

monitoring must meet the same requirements set forth in §141.560(a) through (d) and §141.561. 

§ 141.563 What follow-up action is my system required to take based on continuous 

turbidity monitoring? 

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Follow-up action is required according to the following tables: 

If * * * Your system must * * *

(a) The turbidity of an individual filter 

(or the turbidity of combined filter 

effluent (CFE) for systems with 2 

filters that monitor CFE in lieu of 

individual filters) exceeds 1.0 NTU in 

two consecutive recordings 15 

minutes apart

Report to the State by the 10th of the 

following month and include the filter 

number(s), corresponding date(s), 

turbidity value(s) which exceeded 1.0 

NTU, and the cause (if known) for the 

exceedance(s).

If a system was 

required to report to 

the State * * * Your system must * * *

(b) For three months 

in a row and turbidity 

exceeded 1.0 NTU in 

two consecutive 

recordings 15 minutes 

apart at the same 

filter (or CFE for 

systems with 2 filters 

that monitor CFE in 

lieu of individual 

filters)

Conduct a self-assessment of the filter(s) within 14 

days of the day the filter exceeded 1.0 NTU in two 

consecutive measurements for the third straight month 

unless a CPE as specified in paragraph (c) of this 

section was required. Systems with 2 filters that 

monitor CFE in lieu of individual filters must conduct a 

self assessment on both filters. The self-assessment 

must consist of at least the following components: 

assessment of filter performance; development of a 

filter profile; identification and prioritization of factors 

limiting filter performance; assessment of the 

applicability of corrections; and preparation of a filter 

self-assessment report.

(c) For two months in 

a row and turbidity 

exceeded 2.0 NTU in 

2 consecutive 

recordings 15 minutes 

apart at the same 

filter (or CFE for 

systems with 2 filters 

that monitor CFE in 

lieu of individual 

filters)

Arrange to have a comprehensive performance 

evaluation (CPE) conducted by the State or a third 

party approved by the State not later than 60 days 

following the day the filter exceeded 2.0 NTU in two 

consecutive measurements for the second straight 

month. If a CPE has been completed by the State or a 

third party approved by the State within the 12 prior 

months or the system and State are jointly 

participating in an ongoing Comprehensive Technical 

Assistance (CTA) project at the system, a new CPE is 

not required. If conducted, a CPE must be completed 

and submitted to the State no later than 120 days 

following the day the filter exceeded 2.0 NTU in two 

consecutive measurements for the second straight 

month.

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[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004] 

§ 141.564 My system practices lime softening—is there any special provision 

regarding my individual filter turbidity monitoring? 

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If your system utilizes lime softening, you may apply to the State for alternative turbidity exceedance 

levels for the levels specified in the table in §141.563. You must be able to demonstrate to the State that 

higher turbidity levels are due to lime carryover only, and not due to degraded filter performance. 

Reporting and Recordkeeping Requirements 

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§ 141.570 What does subpart T require that my system report to the State? 

 top

This subpart T requires your system to report several items to the State. The following table describes 

the items which must be reported and the frequency of reporting. Your system is required to report the 

information described in the following table, if it is subject to the specific requirement shown in the first 

column. 

Corresponding 

requirement

Description of information to 

report Frequency

(a) Combined 

Filter Effluent 

Requirements 

(§§141.550–

141.553)

(1) The total number of filtered 

water turbidity measurements 

taken during the month

By the 10th of the 

following month.

 (2) The number and percentage 

of filtered water turbidity 

measurements taken during the 

month which are less than or 

equal to your system's required 

95th percentile limit

By the 10th of the 

following month.

 (3) The date and value of any 

turbidity measurements taken 

during the month which exceed 

the maximum turbidity value for 

your filtration system

By the 10th of the 

following month.

(b) Individual 

Turbidity 

Requirements 

(§§141.560–

141.564)

(1) That your system conducted 

individual filter turbidity 

monitoring during the month

By the 10th of the 

following month.

 (2) The filter number(s), 

corresponding date(s), and the 

turbidity value(s) which exceeded 

1.0 NTU during the month, and 

the cause (if known) for the 

exceedance(s), but only if 2 

consecutive measurements 

exceeded 1.0 NTU

By the 10th of the 

following month.

 (3) If a self-assessment is 

required, the date that it was 

triggered and the date that it was 

completed

By the 10th of the 

following month (or 14 

days after the selfassessment was 

triggered only if the selfassessment was 

triggered during the last 

four days of the month)

 (4) If a CPE is required, that the 

CPE is required and the date that 

it was triggered

By the 10th of the 

following month.

 (5) Copy of completed CPE 

report

Within 120 days after 

the CPE was triggered.

(c) Disinfection 

Profiling 

(§§141.530–

141.536)

(1) Results of optional monitoring 

which show TTHM levels <0.064 

mg/l and HAA5 levels <0.048 

mg/l (Only if your system wishes 

to forgo profiling) or that your 

system has begun disinfection 

profiling

(i) For systems serving 

500–9,999 by July 1, 

2003; 

(ii) For systems serving 

fewer than 500 by 

January 1, 2004.

(d) Disinfection (1) A description of the proposed Anytime your system is 

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[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38857, June 29, 2004] 

§ 141.571 What records does subpart T require my system to keep? 

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Your system must keep several types of records based on the requirements of subpart T, in addition to 

recordkeeping requirements under §141.75. The following table describes the necessary records, the 

length of time these records must be kept, and for which requirement the records pertain. Your system is 

required to maintain records described in this table, if it is subject to the specific requirement shown in 

the first column. 

Subpart U—Initial Distribution System Evaluations 

 top

Source: 71 FR 483, Jan. 4, 2006, unless otherwise noted. 

§ 141.600 General requirements. 

 top

(a) The requirements of subpart U of this part constitute national primary drinking water regulations. The 

regulations in this subpart establish monitoring and other requirements for identifying subpart V 

compliance monitoring locations for determining compliance with maximum contaminant levels for total 

trihalomethanes (TTHM) and haloacetic acids (five)(HAA5). You must use an Initial Distribution System 

Evaluation (IDSE) to determine locations with representative high TTHM and HAA5 concentrations 

throughout your distribution system. IDSEs are used in conjunction with, but separate from, subpart L 

compliance monitoring, to identify and select subpart V compliance monitoring locations. 

(b) Applicability. You are subject to these requirements if your system is a community water system that 

uses a primary or residual disinfectant other than ultraviolet light or delivers water that has been treated 

with a primary or residual disinfectant other than ultraviolet light; or if your system is a nontransient 

noncommunity water system that serves at least 10,000 people and uses a primary or residual 

disinfectant other than ultraviolet light or delivers water that has been treated with a primary or residual 

disinfectant other than ultraviolet light. 

(c) Schedule. (1) You must comply with the requirements of this subpart on the schedule in the table in 

this paragraph (c)(1). 

Benchmarking 

(§§141.540–

141.544)

change in disinfection, your 

system's disinfection profile for 

Giardia lamblia (and, if 

necessary, viruses) and 

disinfection benchmark, and an 

analysis of how the proposed 

change will affect the current 

levels of disinfection

considering a significant 

change to its 

disinfection practice.

Corresponding 

requirement

Description of necessary 

records

Duration of time 

records must be 

kept

(a) Individual Filter 

Turbidity Requirements 

(§§141.560–141.564)

Results of individual filter 

monitoring

At least 3 years.

(b) Disinfection Profiling 

(§§141.530–141.536)

Results of Profile 

(including raw data and 

analysis)

Indefinitely.

(c) Disinfection 

Benchmarking 

(§§141.540–141.544)

Benchmark (including raw 

data and analysis)

Indefinitely.

If you serve 

this 

population

You must submit your 

standard monitoring 

plan or system specific 

study plan1or 40/30 

certification2to the State 

by or receive very small 

system waiver from 

State

You must 

complete your 

standard 

monitoring or 

system specific 

study by

You must 

submit your 

IDSE report to 

the State by3

Systems that are not part of a combined distribution system and 

systems that serve the largest population in the combined distribution 

system

(i) ≥100,000 October 1, 2006 September 30, 

2008

January 1, 2009.

(ii) 50,000–

99,999

April 1, 2007 March 31, 2009 July 1, 2009.

(iii) 10,000– October 1, 2007 September 30, January 1, 2010.

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1If, within 12 months after the date identified in this column, the State does not approve your plan or 

notify you that it has not yet completed its review, you may consider the plan that you submitted as 

approved. You must implement that plan and you must complete standard monitoring or a system 

specific study no later than the date identified in the third column. 

2You must submit your 40/30 certification under §141.603 by the date indicated.

3If, within three months after the date identified in this column (nine months after the date identified in 

this column if you must comply on the schedule in paragraph (c)(1)(iii) of this section), the State does not 

approve your IDSE report or notify you that it has not yet completed its review, you may consider the 

report that you submitted as approved and you must implement the recommended subpart V monitoring 

as required. 

(2) For the purpose of the schedule in paragraph (c)(1) of this section, the State may determine that the 

combined distribution system does not include certain consecutive systems based on factors such as 

receiving water from a wholesale system only on an emergency basis or receiving only a small 

percentage and small volume of water from a wholesale system. The State may also determine that the 

combined distribution system does not include certain wholesale systems based on factors such as 

delivering water to a consecutive system only on an emergency basis or delivering only a small 

percentage and small volume of water to a consecutive system. 

(d) You must conduct standard monitoring that meets the requirements in §141.601, or a system specific 

study that meets the requirements in §141.602, or certify to the State that you meet 40/30 certification 

criteria under §141.603, or qualify for a very small system waiver under §141.604. 

(1) You must have taken the full complement of routine TTHM and HAA5 compliance samples required 

of a system with your population and source water under subpart L of this part (or you must have taken 

the full complement of reduced TTHM and HAA5 compliance samples required of a system with your 

population and source water under subpart L if you meet reduced monitoring criteria under subpart L of 

this part) during the period specified in §141.603(a) to meet the 40/30 certification criteria in §141.603. 

You must have taken TTHM and HAA5 samples under §§141.131 and 141.132 to be eligible for the very 

small system waiver in §141.604. 

(2) If you have not taken the required samples, you must conduct standard monitoring that meets the 

requirements in §141.601, or a system specific study that meets the requirements in §141.602. 

(e) You must use only the analytical methods specified in §141.131, or otherwise approved by EPA for 

monitoring under this subpart, to demonstrate compliance with the requirements of this subpart. 

(f) IDSE results will not be used for the purpose of determining compliance with MCLs in §141.64. 

§ 141.601 Standard monitoring. 

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(a) Standard monitoring plan. Your standard monitoring plan must comply with paragraphs (a)(1) 

through (a)(4) of this section. You must prepare and submit your standard monitoring plan to the State 

according to the schedule in §141.600(c). 

(1) Your standard monitoring plan must include a schematic of your distribution system (including 

distribution system entry points and their sources, and storage facilities), with notes indicating locations 

and dates of all projected standard monitoring, and all projected subpart L compliance monitoring. 

(2) Your standard monitoring plan must include justification of standard monitoring location selection and 

a summary of data you relied on to justify standard monitoring location selection. 

(3) Your standard monitoring plan must specify the population served and system type (subpart H or 

ground water). 

(4) You must retain a complete copy of your standard monitoring plan submitted under this paragraph 

(a), including any State modification of your standard monitoring plan, for as long as you are required to 

retain your IDSE report under paragraph (c)(4) of this section. 

(b) Standard monitoring. (1) You must monitor as indicated in the table in this paragraph (b)(1). You 

must collect dual sample sets at each monitoring location. One sample in the dual sample set must be 

analyzed for TTHM. The other sample in the dual sample set must be analyzed for HAA5. You must 

conduct one monitoring period during the peak historical month for TTHM levels or HAA5 levels or the 

month of warmest water temperature. You must review available compliance, study, or operational data 

to determine the peak historical month for TTHM or HAA5 levels or warmest water temperature. 

49,999 2009

(iv) <10,000 

(CWS Only)

April 1, 2008 March 31, 2010 July 1, 2010.

Other systems that are part of a combined distribution system

(v) Wholesale 

system or 

consecutive 

system

—at the same time as the 

system with the earliest 

compliance date in the 

combined distribution 

system

—at the same 

time as the 

system with the 

earliest 

compliance date 

in the combined 

distribution 

system

—at the same 

time as the 

system with the 

earliest 

compliance date 

in the combined 

distribution 

system.

Source Population 

Monitoring 

periods 

and 

frequency 

Distribution system monitoring locations1

Total per Near Average High High 

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1A dual sample set ( i.e. , a TTHM and an HAA5 sample) must be taken at each monitoring location 

during each monitoring period. 

2The peak historical month is the month with the highest TTHM or HAA5 levels or the warmest water 

temperature. 

(2) You must take samples at locations other than the existing subpart L monitoring locations. Monitoring 

locations must be distributed throughout the distribution system. 

(3) If the number of entry points to the distribution system is fewer than the specified number of entry 

point monitoring locations, excess entry point samples must be replaced equally at high TTHM and 

HAA5 locations. If there is an odd extra location number, you must take a sample at a high TTHM 

location. If the number of entry points to the distribution system is more than the specified number of 

entry point monitoring locations, you must take samples at entry points to the distribution system having 

the highest annual water flows. 

(4) Your monitoring under this paragraph (b) may not be reduced under the provisions of §141.29 and 

the State may not reduce your monitoring using the provisions of §142.16(m). 

(c) IDSE report. Your IDSE report must include the elements required in paragraphs (c)(1) through (c)(4) 

of this section. You must submit your IDSE report to the State according to the schedule in §141.600(c). 

(1) Your IDSE report must include all TTHM and HAA5 analytical results from subpart L compliance 

monitoring and all standard monitoring conducted during the period of the IDSE as individual analytical 

results and LRAAs presented in a tabular or spreadsheet format acceptable to the State. If changed 

from your standard monitoring plan submitted under paragraph (a) of this section, your report must also 

include a schematic of your distribution system, the population served, and system type (subpart H or 

ground water). 

(2) Your IDSE report must include an explanation of any deviations from your approved standard 

monitoring plan. 

water 

type

size 

category

of 

sampling

monitoring 

period

entry 

points

residence

time

TTHM 

locations

HAA5 

locations

Subpart 

H

<500 

consecutive 

systems

one (during 

peak 

historical 

month)2

21 1

<500 nonconsecutive 

systems

2 11

500–3,300 

consecutive 

systems

four (every 

90 days)

21 1

500–3,300 

nonconsecutive 

systems

2 11

3,301–

9,999

4 121

10,000–

49,999

six (every 

60 days)

81 2 3 2

50,000–

249,999

16 3 4 5 4

250,000–

999,999

24 4 6 8 6

1,000,000–

4,999,999

32 6 8 10 8

≥5,000,000 40 8 10 12 10

Ground 

Water

<500 

consecutive 

systems

one (during 

peak 

historical 

month)2

21 1

<500 nonconsecutive 

systems

2 11

500–9,999 four (every 

90 days)

2 11

10,000–

99,999

61 1 2 2

100,000–

499,999

81 1 3 3

≥500,000 12 2 2 4 4

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(3) You must recommend and justify subpart V compliance monitoring locations and timing based on the 

protocol in §141.605. 

(4) You must retain a complete copy of your IDSE report submitted under this section for 10 years after 

the date that you submitted your report. If the State modifies the subpart V monitoring requirements that 

you recommended in your IDSE report or if the State approves alternative monitoring locations, you 

must keep a copy of the State's notification on file for 10 years after the date of the State's notification. 

You must make the IDSE report and any State notification available for review by the State or the public. 

§ 141.602 System specific studies. 

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(a) System specific study plan. Your system specific study plan must be based on either existing 

monitoring results as required under paragraph (a)(1) of this section or modeling as required under 

paragraph (a)(2) of this section. You must prepare and submit your system specific study plan to the 

State according to the schedule in §141.600(c). 

(1) Existing monitoring results. You may comply by submitting monitoring results collected before you 

are required to begin monitoring under §141.600(c). The monitoring results and analysis must meet the 

criteria in paragraphs (a)(1)(i) and (a)(1)(ii) of this section. 

(i) Minimum requirements. (A) TTHM and HAA5 results must be based on samples collected and 

analyzed in accordance with §141.131. Samples must be collected no earlier than five years prior to the 

study plan submission date. 

(B) The monitoring locations and frequency must meet the conditions identified in this paragraph (a)(1)(i)

(B). Each location must be sampled once during the peak historical month for TTHM levels or HAA5 

levels or the month of warmest water temperature for every 12 months of data submitted for that 

location. Monitoring results must include all subpart L compliance monitoring results plus additional 

monitoring results as necessary to meet minimum sample requirements. 

(ii) Reporting monitoring results. You must report the information in this paragraph (a)(1)(ii). 

(A) You must report previously collected monitoring results and certify that the reported monitoring 

results include all compliance and non-compliance results generated during the time period beginning 

with the first reported result and ending with the most recent subpart L results. 

(B) You must certify that the samples were representative of the entire distribution system and that 

treatment, and distribution system have not changed significantly since the samples were collected. 

(C) Your study monitoring plan must include a schematic of your distribution system (including 

distribution system entry points and their sources, and storage facilities), with notes indicating the 

locations and dates of all completed or planned system specific study monitoring. 

(D) Your system specific study plan must specify the population served and system type (subpart H or 

ground water). 

(E) You must retain a complete copy of your system specific study plan submitted under this paragraph 

(a)(1), including any State modification of your system specific study plan, for as long as you are 

required to retain your IDSE report under paragraph (b)(5) of this section. 

(F) If you submit previously collected data that fully meet the number of samples required under 

paragraph (a)(1)(i)(B) of this section and the State rejects some of the data, you must either conduct 

additional monitoring to replace rejected data on a schedule the State approves or conduct standard 

monitoring under §141.601. 

(2) Modeling. You may comply through analysis of an extended period simulation hydraulic model. The 

extended period simulation hydraulic model and analysis must meet the criteria in this paragraph (a)(2). 

(i) Minimum requirements. (A) The model must simulate 24 hour variation in demand and show a 

consistently repeating 24 hour pattern of residence time. 

System 

Type

Population size 

category

Number of 

monitoring 

locations

Number of 

samples

TTHM HAA5

Subpart H:

 <500 3 3 3

 500–3,300 3 9 9

 3,301–9,999 6 36 36

 10,000–49,999 12 72 72

 50,000–249,999 24 144 144

 250,000–999,999 36 216 216

 1,000,000–

4,999,999

48 288 288

 ≥ 5,000,000 60 360 360

Ground 

Water:

 <500 3 3 3

 500–9,999 3 9 9

 10,000–99,999 12 48 48

 100,000–499,999 18 72 72

 ≥ 500,000 24 96 96

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(B) The model must represent the criteria listed in paragraphs (a)(2)(i)(B)(1) through (9) of this section. 

(1) 75% of pipe volume; 

(2) 50% of pipe length; 

(3) All pressure zones; 

(4) All 12-inch diameter and larger pipes; 

(5) All 8-inch and larger pipes that connect pressure zones, influence zones from different sources, 

storage facilities, major demand areas, pumps, and control valves, or are known or expected to be 

significant conveyors of water; 

(6) All 6-inch and larger pipes that connect remote areas of a distribution system to the main portion of 

the system; 

(7) All storage facilities with standard operations represented in the model; and 

(8) All active pump stations with controls represented in the model; and 

(9) All active control valves. 

(C) The model must be calibrated, or have calibration plans, for the current configuration of the 

distribution system during the period of high TTHM formation potential. All storage facilities must be 

evaluated as part of the calibration process. All required calibration must be completed no later than 12 

months after plan submission. 

(ii) Reporting modeling. Your system specific study plan must include the information in this paragraph 

(a)(2)(ii). 

(A) Tabular or spreadsheet data demonstrating that the model meets requirements in paragraph (a)(2)(i)

(B) of this section. 

(B) A description of all calibration activities undertaken, and if calibration is complete, a graph of 

predicted tank levels versus measured tank levels for the storage facility with the highest residence time 

in each pressure zone, and a time series graph of the residence time at the longest residence time 

storage facility in the distribution system showing the predictions for the entire simulation period ( i.e. , 

from time zero until the time it takes to for the model to reach a consistently repeating pattern of 

residence time). 

(C) Model output showing preliminary 24 hour average residence time predictions throughout the 

distribution system. 

(D) Timing and number of samples representative of the distribution system planned for at least one 

monitoring period of TTHM and HAA5 dual sample monitoring at a number of locations no less than 

would be required for the system under standard monitoring in §141.601 during the historical month of 

high TTHM. These samples must be taken at locations other than existing subpart L compliance 

monitoring locations. 

(E) Description of how all requirements will be completed no later than 12 months after you submit your 

system specific study plan. 

(F) Schematic of your distribution system (including distribution system entry points and their sources, 

and storage facilities), with notes indicating the locations and dates of all completed system specific 

study monitoring (if calibration is complete) and all subpart L compliance monitoring. 

(G) Population served and system type (subpart H or ground water). 

(H) You must retain a complete copy of your system specific study plan submitted under this paragraph 

(a)(2), including any State modification of your system specific study plan, for as long as you are 

required to retain your IDSE report under paragraph (b)(7) of this section. 

(iii) If you submit a model that does not fully meet the requirements under paragraph (a)(2) of this 

section, you must correct the deficiencies and respond to State inquiries concerning the model. If you fail 

to correct deficiencies or respond to inquiries to the State's satisfaction, you must conduct standard 

monitoring under §141.601. 

(b) IDSE report. Your IDSE report must include the elements required in paragraphs (b)(1) through (b)(6) 

of this section. You must submit your IDSE report according to the schedule in §141.600(c). 

(1) Your IDSE report must include all TTHM and HAA5 analytical results from subpart L compliance 

monitoring and all system specific study monitoring conducted during the period of the system specific 

study presented in a tabular or spreadsheet format acceptable to the State. If changed from your system 

specific study plan submitted under paragraph (a) of this section, your IDSE report must also include a 

schematic of your distribution system, the population served, and system type (subpart H or ground 

water). 

(2) If you used the modeling provision under paragraph (a)(2) of this section, you must include final 

information for the elements described in paragraph (a)(2)(ii) of this section, and a 24-hour time series 

graph of residence time for each subpart V compliance monitoring location selected. 

(3) You must recommend and justify subpart V compliance monitoring locations and timing based on the 

protocol in §141.605. 

(4) Your IDSE report must include an explanation of any deviations from your approved system specific 

study plan. 

(5) Your IDSE report must include the basis (analytical and modeling results) and justification you used 

to select the recommended subpart V monitoring locations. 

(6) You may submit your IDSE report in lieu of your system specific study plan on the schedule identified 

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in §141.600(c) for submission of the system specific study plan if you believe that you have the 

necessary information by the time that the system specific study plan is due. If you elect this approach, 

your IDSE report must also include all information required under paragraph (a) of this section. 

(7) You must retain a complete copy of your IDSE report submitted under this section for 10 years after 

the date that you submitted your IDSE report. If the State modifies the subpart V monitoring 

requirements that you recommended in your IDSE report or if the State approves alternative monitoring 

locations, you must keep a copy of the State's notification on file for 10 years after the date of the State's 

notification. You must make the IDSE report and any State notification available for review by the State 

or the public. 

§ 141.603 40/30 certification. 

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(a) Eligibility. You are eligible for 40/30 certification if you had no TTHM or HAA5 monitoring violations 

under subpart L of this part and no individual sample exceeded 0.040 mg/L for TTHM or 0.030 mg/L for 

HAA5 during an eight consecutive calendar quarter period beginning no earlier than the date specified in 

this paragraph (a). 

1Unless you are on reduced monitoring under subpart L of this part and were not required to monitor 

during the specified period. If you did not monitor during the specified period, you must base your 

eligibility on compliance samples taken during the 12 months preceding the specified period. 

(b) 40/30 certification. (1) You must certify to your State that every individual compliance sample taken 

under subpart L of this part during the periods specified in paragraph (a) of this section were ≤0.040 

mg/L for TTHM and ≤0.030 mg/L for HAA5, and that you have not had any TTHM or HAA5 monitoring 

violations during the period specified in paragraph (a) of this section. 

(2) The State may require you to submit compliance monitoring results, distribution system schematics, 

and/or recommended subpart V compliance monitoring locations in addition to your certification. If you 

fail to submit the requested information, the State may require standard monitoring under §141.601 or a 

system specific study under §141.602. 

(3) The State may still require standard monitoring under §141.601 or a system specific study under 

§141.602 even if you meet the criteria in paragraph (a) of this section. 

(4) You must retain a complete copy of your certification submitted under this section for 10 years after 

the date that you submitted your certification. You must make the certification, all data upon which the 

certification is based, and any State notification available for review by the State or the public. 

§ 141.604 Very small system waivers. 

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(a) If you serve fewer than 500 people and you have taken TTHM and HAA5 samples under subpart L of 

this part, you are not required to comply with this subpart unless the State notifies you that you must 

conduct standard monitoring under §141.601 or a system specific study under §141.602. 

(b) If you have not taken TTHM and HAA5 samples under subpart L of this part or if the State notifies 

you that you must comply with this subpart, you must conduct standard monitoring under §141.601 or a 

system specific study under §141.602. 

§ 141.605 Subpart V compliance monitoring location recommendations. 

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(a) Your IDSE report must include your recommendations and justification for where and during what 

month(s) TTHM and HAA5 monitoring for subpart V of this part should be conducted. You must base 

your recommendations on the criteria in paragraphs (b) through (e) of this section. 

(b) You must select the number of monitoring locations specified in the table in this paragraph (b). You 

will use these recommended locations as subpart V routine compliance monitoring locations, unless 

State requires different or additional locations. You should distribute locations throughout the distribution 

system to the extent possible. 

If your 40/30 

certification is 

due

Then your eligibility for 40/30 certification is based on 

eight consecutive calendar quarters of subpart L 

compliance monitoring results beginning no earlier 

than1

(1) October 1, 

2006

January 2004.

(2) April 1, 2007 January 2004.

(3) October 1, 

2007

January 2005.

(4) April 1, 2008 January 2005.

Source 

water 

type

Population 

size 

category

Monitoring 

frequency1

Distribution system monitoring location

Total per 

monitoring 

period2

Highest 

TTHM 

locations

Highest 

HAA5 

locations

Existing 

subpart L 

compliance 

locations

Subpart 

H:

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1All systems must monitor during month of highest DBP concentrations.

2Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, 

except for subpart H systems serving 500–3,300. Ground water systems serving 500–9,999 on annual 

monitoring must take dual sample sets at each monitoring location. All other systems on annual 

monitoring and subpart H systems serving 500–3,300 are required to take individual TTHM and HAA5 

samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 

concentrations, respectively. For systems serving fewer than 500 people, only one location with a dual 

sample set per monitoring period is needed if the highest TTHM and HAA5 concentrations occur at the 

same location and month. 

(c) You must recommend subpart V compliance monitoring locations based on standard monitoring 

results, system specific study results, and subpart L compliance monitoring results. You must follow the 

protocol in paragraphs (c)(1) through (c)(8) of this section. If required to monitor at more than eight 

locations, you must repeat the protocol as necessary. If you do not have existing subpart L compliance 

monitoring results or if you do not have enough existing subpart L compliance monitoring results, you 

must repeat the protocol, skipping the provisions of paragraphs (c)(3) and (c)(7) of this section as 

necessary, until you have identified the required total number of monitoring locations. 

(1) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location. 

(2) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location. 

(3) Existing subpart L average residence time compliance monitoring location (maximum residence time 

compliance monitoring location for ground water systems) with the highest HAA5 LRAA not previously 

selected as a subpart V monitoring location. 

(4) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location. 

(5) Location with the highest TTHM LRAA not previously selected as a subpart V monitoring location. 

(6) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location. 

(7) Existing subpart L average residence time compliance monitoring location (maximum residence time 

compliance monitoring location for ground water systems) with the highest TTHM LRAA not previously 

selected as a subpart V monitoring location. 

(8) Location with the highest HAA5 LRAA not previously selected as a subpart V monitoring location. 

(d) You may recommend locations other than those specified in paragraph (c) of this section if you 

include a rationale for selecting other locations. If the State approves the alternate locations, you must 

monitor at these locations to determine compliance under subpart V of this part. 

(e) Your recommended schedule must include subpart V monitoring during the peak historical month for 

TTHM and HAA5 concentration, unless the State approves another month. Once you have identified the 

peak historical month, and if you are required to conduct routine monitoring at least quarterly, you must 

schedule subpart V compliance monitoring at a regular frequency of every 90 days or fewer. 

[71 FR 483, Jan. 4, 2006, as amended at 74 FR 30958, June 29, 2009] 

Subpart V—Stage 2 Disinfection Byproducts Requirements 

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Source: 71 FR 488, Jan. 4, 2006, unless otherwise noted. 

§ 141.620 General requirements. 

 <500 per year 2 1 1

 500–3,300 per quarter 2 1 1

 3,301–

9,999

per quarter 2 1 1

 10,000–

49,999

per quarter 4 2 1 1

 50,000–

249,999

per quarter 8 3 3 2

 250,000–

999,999

per quarter 12 5 4 3

 1,000,000–

4,999,999

per quarter 16 6 6 4

 ≥5,000,000 per quarter 20 8 7 5

Ground 

water:

 <500 per year 2 1 1

 500–9,999 per year 2 1 1

 10,000–

99,999

per quarter 4 2 1 1

 100,000–

499,999

per quarter 6 3 2 1

 ≥500,000 per quarter 8 3 3 2

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(a) General. The requirements of subpart V of this part constitute national primary drinking water 

regulations. The regulations in this subpart establish monitoring and other requirements for achieving 

compliance with maximum contaminant levels based on locational running annual averages (LRAA) for 

total trihalomethanes (TTHM) and haloacetic acids (five)(HAA5), and for achieving compliance with 

maximum residual disinfectant residuals for chlorine and chloramine for certain consecutive systems. 

(b) Applicability. You are subject to these requirements if your system is a community water system or a 

nontransient noncommunity water system that uses a primary or residual disinfectant other than 

ultraviolet light or delivers water that has been treated with a primary or residual disinfectant other than 

ultraviolet light. 

(c) Schedule. You must comply with the requirements in this subpart on the schedule in the following 

table based on your system type. 

1The State may grant up to an additional 24 months for compliance with MCLs and operational 

evaluation levels if you require capital improvements to comply with an MCL. 

(6) Your monitoring frequency is specified in §141.621(a)(2). 

(i) If you are required to conduct quarterly monitoring, you must begin monitoring in the first full calendar 

quarter that includes the compliance date in the table in this paragraph (c). 

(ii) If you are required to conduct monitoring at a frequency that is less than quarterly, you must begin 

monitoring in the calendar month recommended in the IDSE report prepared under §141.601 or 

§141.602 or the calendar month identified in the subpart V monitoring plan developed under §141.622 

no later than 12 months after the compliance date in this table. 

(7) If you are required to conduct quarterly monitoring, you must make compliance calculations at the 

end of the fourth calendar quarter that follows the compliance date and at the end of each subsequent 

quarter (or earlier if the LRAA calculated based on fewer than four quarters of data would cause the 

MCL to be exceeded regardless of the monitoring results of subsequent quarters). If you are required to 

conduct monitoring at a frequency that is less than quarterly, you must make compliance calculations 

beginning with the first compliance sample taken after the compliance date. 

(8) For the purpose of the schedule in this paragraph (c), the State may determine that the combined 

distribution system does not include certain consecutive systems based on factors such as receiving 

water from a wholesale system only on an emergency basis or receiving only a small percentage and 

small volume of water from a wholesale system. The State may also determine that the combined 

distribution system does not include certain wholesale systems based on factors such as delivering 

water to a consecutive system only on an emergency basis or delivering only a small percentage and 

small volume of water to a consecutive system. 

(d) Monitoring and compliance —(1) Systems required to monitor quarterly. To comply with subpart V 

MCLs in §141.64(b)(2), you must calculate LRAAs for TTHM and HAA5 using monitoring results 

collected under this subpart and determine that each LRAA does not exceed the MCL. If you fail to 

complete four consecutive quarters of monitoring, you must calculate compliance with the MCL based 

on the average of the available data from the most recent four quarters. If you take more than one 

sample per quarter at a monitoring location, you must average all samples taken in the quarter at that 

location to determine a quarterly average to be used in the LRAA calculation. 

(2) Systems required to monitor yearly or less frequently. To determine compliance with subpart V MCLs 

in §141.64(b)(2), you must determine that each sample taken is less than the MCL. If any sample 

exceeds the MCL, you must comply with the requirements of §141.625. If no sample exceeds the MCL, 

the sample result for each monitoring location is considered the LRAA for that monitoring location. 

(e) Violation. You are in violation of the monitoring requirements for each quarter that a monitoring result 

would be used in calculating an LRAA if you fail to monitor. 

[71 FR 488, Jan. 4, 2006; 71 FR 4645, Jan. 27, 2006] 

§ 141.621 Routine monitoring. 

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If you are this type of 

system

You must comply with subpart V monitoring 

by:1

Systems that are not part of a combined distribution system and 

systems that serve the largest population in the combined distribution 

system

(1) System serving ≥

100,000

April 1, 2012.

(2) System serving 

50,000–99,999

October 1, 2012.

(3) System serving 

10,000–49,999

October 1, 2013.

(4) System serving < 

10,000

October 1, 2013 if no Cryptosporidium monitoring 

is required under §141.701(a)(4) or 

October 1, 2014 if Cryptosporidium monitoring is 

required under §141.701(a)(4) or (a)(6)

Other systems that are part of a combined distribution system

(5) Consecutive system 

or wholesale system

—at the same time as the system with the earliest 

compliance date in the combined distribution 

system.

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(a) Monitoring. (1) If you submitted an IDSE report, you must begin monitoring at the locations and 

months you have recommended in your IDSE report submitted under §141.605 following the schedule in 

§141.620(c), unless the State requires other locations or additional locations after its review. If you 

submitted a 40/30 certification under §141.603 or you qualified for a very small system waiver under 

§141.604 or you are a nontransient noncommunity water system serving <10,000, you must monitor at 

the location(s) and dates identified in your monitoring plan in §141.132(f), updated as required by 

§141.622. 

(2) You must monitor at no fewer than the number of locations identified in this paragraph (a)(2). 

1All systems must monitor during month of highest DBP concentrations.

2Systems on quarterly monitoring must take dual sample sets every 90 days at each monitoring location, 

except for subpart H systems serving 500–3,300. Ground water systems serving 500–9,999 on annual 

monitoring must take dual sample sets at each monitoring location. All other systems on annual 

monitoring and subpart H systems serving 500–3,300 are required to take individual TTHM and HAA5 

samples (instead of a dual sample set) at the locations with the highest TTHM and HAA5 

concentrations, respectively. For systems serving fewer than 500 people, only one location with a dual 

sample set per monitoring period is needed if the highest TTHM and HAA5 concentrations occur at the 

same location and month. 

(3) If you are an undisinfected system that begins using a disinfectant other than UV light after the dates 

in subpart U of this part for complying with the Initial Distribution System Evaluation requirements, you 

must consult with the State to identify compliance monitoring locations for this subpart. You must then 

develop a monitoring plan under §141.622 that includes those monitoring locations. 

(b) Analytical methods. You must use an approved method listed in §141.131 for TTHM and HAA5 

analyses in this subpart. Analyses must be conducted by laboratories that have received certification by 

EPA or the State as specified in §141.131. 

[71 FR 488, Jan. 4, 2006, as amended at 74 FR 30958, June 29, 2009] 

§ 141.622 Subpart V monitoring plan. 

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(a)(1) You must develop and implement a monitoring plan to be kept on file for State and public review. 

The monitoring plan must contain the elements in paragraphs (a)(1)(i) through (a)(1)(iv) of this section 

and be complete no later than the date you conduct your initial monitoring under this subpart. 

(i) Monitoring locations; 

(ii) Monitoring dates; 

(iii) Compliance calculation procedures; and 

(iv) Monitoring plans for any other systems in the combined distribution system if the State has reduced 

monitoring requirements under the State authority in §142.16(m). 

(2) If you were not required to submit an IDSE report under either §141.601 or §141.602, and you do not 

have sufficient subpart L monitoring locations to identify the required number of subpart V compliance 

monitoring locations indicated in §141.605(b), you must identify additional locations by alternating 

selection of locations representing high TTHM levels and high HAA5 levels until the required number of 

compliance monitoring locations have been identified. You must also provide the rationale for identifying 

the locations as having high levels of TTHM or HAA5. If you have more subpart L monitoring locations 

than required for subpart V compliance monitoring in §141.605(b), you must identify which locations you 

will use for subpart V compliance monitoring by alternating selection of locations representing high 

TTHM levels and high HAA5 levels until the required number of subpart V compliance monitoring 

locations have been identified. 

Source 

water type

Population 

size category

Monitoring 

Frequency1

Distribution system 

monitoring location total per 

monitoring period2

Subpart H:

 <500 per year 2

 500–3,300 per quarter 2

 3,301–9,999 per quarter 2

 10,000–49,999 per quarter 4

 50,000–249,999 per quarter 8

 250,000–

999,999

per quarter 12

 1,000,000–

4,999,999

per quarter 16

 ≥ 5,000,000 per quarter 20

Ground 

Water:

 <500 per year 2

 500–9,999 per year 2

 10,000–99,999 per quarter 4

 100,000–

499,999

per quarter 6

 ≥ 500,000 per quarter 8

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(b) If you are a subpart H system serving > 3,300 people, you must submit a copy of your monitoring 

plan to the State prior to the date you conduct your initial monitoring under this subpart, unless your 

IDSE report submitted under subpart U of this part contains all the information required by this section. 

(c) You may revise your monitoring plan to reflect changes in treatment, distribution system operations 

and layout (including new service areas), or other factors that may affect TTHM or HAA5 formation, or 

for State-approved reasons, after consultation with the State regarding the need for changes and the 

appropriateness of changes. If you change monitoring locations, you must replace existing compliance 

monitoring locations with the lowest LRAA with new locations that reflect the current distribution system 

locations with expected high TTHM or HAA5 levels. The State may also require modifications in your 

monitoring plan. If you are a subpart H system serving > 3,300 people, you must submit a copy of your 

modified monitoring plan to the State prior to the date you are required to comply with the revised 

monitoring plan. 

§ 141.623 Reduced monitoring. 

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(a) You may reduce monitoring to the level specified in the table in this paragraph (a) any time the LRAA 

is ≤0.040 mg/L for TTHM and ≤0.030 mg/L for HAA5 at all monitoring locations. You may only use data 

collected under the provisions of this subpart or subpart L of this part to qualify for reduced monitoring. 

In addition, the source water annual average TOC level, before any treatment, must be ≤4.0 mg/L at 

each treatment plant treating surface water or ground water under the direct influence of surface water, 

based on monitoring conducted under either §141.132(b)(1)(iii) or §141.132(d). 

Source 

water 

type

Population 

size 

category

Monitoring 

frequency1 Distribution system monitoring 

location per monitoring period

Subpart 

H:

 <500 monitoring may not be reduced.

 500–3,300 per year 1 TTHM and 1 HAA5 sample: one at the 

location and during the quarter with the 

highest TTHM single measurement, one 

at the location and during the quarter with 

the highest HAA5 single measurement; 1 

dual sample set per year if the highest 

TTHM and HAA5 measurements 

occurred at the same location and 

quarter.

 3,301–9,999 per year 2 dual sample sets: one at the location 

and during the quarter with the highest 

TTHM single measurement, one at the 

location and during the quarter with the 

highest HAA5 single measurement.

 10,000–

49,999

per quarter 2 dual sample sets at the locations with 

the highest TTHM and highest HAA5 

LRAAs.

 50,000–

249,999

per quarter 4 dual sample sets—at the locations with 

the two highest TTHM and two highest 

HAA5 LRAAs.

 250,000–

999,999

per quarter 6 dual sample sets—at the locations with 

the three highest TTHM and three 

highest HAA5 LRAAs.

 1,000,000–

4,999,999

per quarter 8 dual sample sets—at the locations with 

the four highest TTHM and four highest 

HAA5 LRAAs.

 ≥ 5,000,000 per quarter 10 dual sample sets—at the locations 

with the five highest TTHM and five 

highest HAA5 LRAAs.

Ground 

Water:

 <500 every third 

year

1 TTHM and 1 HAA5 sample: one at the 

location and during the quarter with the 

highest TTHM single measurement, one 

at the location and during the quarter with 

the highest HAA5 single measurement; 1 

dual sample set per year if the highest 

TTHM and HAA5 measurements 

occurred at the same location and 

quarter.

 500–9,999 per year 1 TTHM and 1 HAA5 sample: one at the 

location and during the quarter with the 

highest TTHM single measurement, one 

at the location and during the quarter with 

the highest HAA5 single measurement; 1 

dual sample set per year if the highest 

TTHM and HAA5 measurements 

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1Systems on quarterly monitoring must take dual sample sets every 90 days.

(b) You may remain on reduced monitoring as long as the TTHM LRAA ≤0.040 mg/L and the HAA5 

LRAA ≤0.030 mg/L at each monitoring location (for systems with quarterly reduced monitoring) or each 

TTHM sample ≤0.060 mg/L and each HAA5 sample ≤0.045 mg/L (for systems with annual or less 

frequent monitoring). In addition, the source water annual average TOC level, before any treatment, 

must be ≤4.0 mg/L at each treatment plant treating surface water or ground water under the direct 

influence of surface water, based on monitoring conducted under either §141.132(b)(1)(iii) or §141.132

(d). 

(c) If the LRAA based on quarterly monitoring at any monitoring location exceeds either 0.040 mg/L for 

TTHM or 0.030 mg/L for HAA5 or if the annual (or less frequent) sample at any location exceeds either 

0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or if the source water annual average TOC level, before 

any treatment, >4.0 mg/L at any treatment plant treating surface water or ground water under the direct 

influence of surface water, you must resume routine monitoring under §141.621 or begin increased 

monitoring if §141.625 applies. 

(d) The State may return your system to routine monitoring at the State's discretion. 

§ 141.624 Additional requirements for consecutive systems. 

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If you are a consecutive system that does not add a disinfectant but delivers water that has been treated 

with a primary or residual disinfectant other than ultraviolet light, you must comply with analytical and 

monitoring requirements for chlorine and chloramines in §141.131 (c) and §141.132(c)(1) and the 

compliance requirements in §141.133(c)(1) beginning April 1, 2009, unless required earlier by the State, 

and report monitoring results under §141.134(c). 

§ 141.625 Conditions requiring increased monitoring. 

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(a) If you are required to monitor at a particular location annually or less frequently than annually under 

§141.621 or §141.623, you must increase monitoring to dual sample sets once per quarter (taken every 

90 days) at all locations if a TTHM sample is >0.080 mg/L or a HAA5 sample is >0.060 mg/L at any 

location. 

(b) You are in violation of the MCL when the LRAA exceeds the subpart V MCLs in §141.64(b)(2), 

calculated based on four consecutive quarters of monitoring (or the LRAA calculated based on fewer 

than four quarters of data if the MCL would be exceeded regardless of the monitoring results of 

subsequent quarters). You are in violation of the monitoring requirements for each quarter that a 

monitoring result would be used in calculating an LRAA if you fail to monitor. 

(c) You may return to routine monitoring once you have conducted increased monitoring for at least four 

consecutive quarters and the LRAA for every monitoring location is ≤0.060 mg/L for TTHM and ≤0.045 

mg/L for HAA5. 

§ 141.626 Operational evaluation levels. 

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(a) You have exceeded the operational evaluation level at any monitoring location where the sum of the 

two previous quarters' TTHM results plus twice the current quarter's TTHM result, divided by 4 to 

determine an average, exceeds 0.080 mg/L, or where the sum of the two previous quarters' HAA5 

results plus twice the current quarter's HAA5 result, divided by 4 to determine an average, exceeds 

0.060 mg/L. 

(b)(1) If you exceed the operational evaluation level, you must conduct an operational evaluation and 

submit a written report of the evaluation to the State no later than 90 days after being notified of the 

analytical result that causes you to exceed the operational evaluation level. The written report must be 

made available to the public upon request. 

(2) Your operational evaluation must include an examination of system treatment and distribution 

operational practices, including storage tank operations, excess storage capacity, distribution system 

flushing, changes in sources or source water quality, and treatment changes or problems that may 

contribute to TTHM and HAA5 formation and what steps could be considered to minimize future 

exceedences. 

(i) You may request and the State may allow you to limit the scope of your evaluation if you are able to 

identify the cause of the operational evaluation level exceedance. 

(ii) Your request to limit the scope of the evaluation does not extend the schedule in paragraph (b)(1) of 

occurred at the same location and 

quarter.

 10,000–

99,999

per year 2 dual sample sets: one at the location 

and during the quarter with the highest 

TTHM single measurement, one at the 

location and during the quarter with the 

highest HAA5 single measurement.

 100,000–

499,999

per quarter 2 dual sample sets; at the locations with 

the highest TTHM and highest HAA5 

LRAAs.

 ≥ 500,000 per quarter 4 dual sample sets at the locations with 

the two highest TTHM and two highest 

HAA5 LRAAs.

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this section for submitting the written report. The State must approve this limited scope of evaluation in 

writing and you must keep that approval with the completed report. 

§ 141.627 Requirements for remaining on reduced TTHM and HAA5 monitoring based 

on subpart L results. 

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You may remain on reduced monitoring after the dates identified in §141.620(c) for compliance with this 

subpart only if you qualify for a 40/30 certification under §141.603 or have received a very small system 

waiver under §141.604, plus you meet the reduced monitoring criteria in §141.623(a), and you do not 

change or add monitoring locations from those used for compliance monitoring under subpart L of this 

part. If your monitoring locations under this subpart differ from your monitoring locations under subpart L 

of this part, you may not remain on reduced monitoring after the dates identified in §141.620(c) for 

compliance with this subpart. 

§ 141.628 Requirements for remaining on increased TTHM and HAA5 monitoring 

based on subpart L results. 

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If you were on increased monitoring under §141.132(b)(1), you must remain on increased monitoring 

until you qualify for a return to routine monitoring under §141.625(c). You must conduct increased 

monitoring under §141.625 at the monitoring locations in the monitoring plan developed under §141.622 

beginning at the date identified in §141.620(c) for compliance with this subpart and remain on increased 

monitoring until you qualify for a return to routine monitoring under §141.625(c). 

§ 141.629 Reporting and recordkeeping requirements. 

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(a) Reporting. (1) You must report the following information for each monitoring location to the State 

within 10 days of the end of any quarter in which monitoring is required: 

(i) Number of samples taken during the last quarter. 

(ii) Date and results of each sample taken during the last quarter. 

(iii) Arithmetic average of quarterly results for the last four quarters for each monitoring location (LRAA), 

beginning at the end of the fourth calendar quarter that follows the compliance date and at the end of 

each subsequent quarter. If the LRAA calculated based on fewer than four quarters of data would cause 

the MCL to be exceeded regardless of the monitoring results of subsequent quarters, you must report 

this information to the State as part of the first report due following the compliance date or anytime 

thereafter that this determination is made. If you are required to conduct monitoring at a frequency that is 

less than quarterly, you must make compliance calculations beginning with the first compliance sample 

taken after the compliance date, unless you are required to conduct increased monitoring under 

§141.625. 

(iv) Whether, based on §141.64(b)(2) and this subpart, the MCL was violated at any monitoring location. 

(v) Any operational evaluation levels that were exceeded during the quarter and, if so, the location and 

date, and the calculated TTHM and HAA5 levels. 

(2) If you are a subpart H system seeking to qualify for or remain on reduced TTHM/HAA5 monitoring, 

you must report the following source water TOC information for each treatment plant that treats surface 

water or ground water under the direct influence of surface water to the State within 10 days of the end 

of any quarter in which monitoring is required: 

(i) The number of source water TOC samples taken each month during last quarter. 

(ii) The date and result of each sample taken during last quarter. 

(iii) The quarterly average of monthly samples taken during last quarter or the result of the quarterly 

sample. 

(iv) The running annual average (RAA) of quarterly averages from the past four quarters. 

(v) Whether the RAA exceeded 4.0 mg/L. 

(3) The State may choose to perform calculations and determine whether the MCL was exceeded or the 

system is eligible for reduced monitoring in lieu of having the system report that information 

(b) Recordkeeping. You must retain any subpart V monitoring plans and your subpart V monitoring 

results as required by §141.33. 

Subpart W—Enhanced Treatment forCryptosporidium 

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Source: 71 FR 769, Jan. 5, 2006, unless otherwise noted. 

General Requirements 

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§ 141.700 General requirements. 

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(a) The requirements of this subpart W are national primary drinking water regulations. The regulations 

in this subpart establish or extend treatment technique requirements in lieu of maximum contaminant 

levels for Cryptosporidium. These requirements are in addition to requirements for filtration and 

disinfection in subparts H, P, and T of this part. 

(b) Applicability. The requirements of this subpart apply to all subpart H systems, which are public water 

systems supplied by a surface water source and public water systems supplied by a ground water 

source under the direct influence of surface water. 

(1) Wholesale systems, as defined in §141.2, must comply with the requirements of this subpart based 

on the population of the largest system in the combined distribution system. 

(2) The requirements of this subpart for filtered systems apply to systems required by National Primary 

Drinking Water Regulations to provide filtration treatment, whether or not the system is currently 

operating a filtration system. 

(3) The requirements of this subpart for unfiltered systems apply only to unfiltered systems that timely 

met and continue to meet the filtration avoidance criteria in subparts H, P, and T of this part, as 

applicable. 

(c) Requirements. Systems subject to this subpart must comply with the following requirements: 

(1) Systems must conduct an initial and a second round of source water monitoring for each plant that 

treats a surface water or GWUDI source. This monitoring may include sampling for Cryptosporidium, E. 

coli, and turbidity as described in §§141.701 through 141.706, to determine what level, if any, of 

additional Cryptosporidium treatment they must provide. 

(2) Systems that plan to make a significant change to their disinfection practice must develop 

disinfection profiles and calculate disinfection benchmarks, as described in §§141.708 through 141.709. 

(3) Filtered systems must determine their Cryptosporidium treatment bin classification as described in 

§141.710 and provide additional treatment for Cryptosporidium, if required, as described in §141.711. All 

unfiltered systems must provide treatment for Cryptosporidium as described in §141.712. Filtered and 

unfiltered systems must implement Cryptosporidium treatment according to the schedule in §141.713. 

(4) Systems with uncovered finished water storage facilities must comply with the requirements to cover 

the facility or treat the discharge from the facility as described in §141.714. 

(5) Systems required to provide additional treatment for Cryptosporidium must implement microbial 

toolbox options that are designed and operated as described in §§141.715 through 141.720. 

(6) Systems must comply with the applicable recordkeeping and reporting requirements described in 

§§141.721 through 141.722. 

(7) Systems must address significant deficiencies identified in sanitary surveys performed by EPA as 

described in §141.723. 

Source Water Monitoring Requirements 

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§ 141.701 Source water monitoring. 

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(a) Initial round of source water monitoring. Systems must conduct the following monitoring on the 

schedule in paragraph (c) of this section unless they meet the monitoring exemption criteria in paragraph 

(d) of this section. 

(1) Filtered systems serving at least 10,000 people must sample their source water for Cryptosporidium, 

E. coli, and turbidity at least monthly for 24 months. 

(2) Unfiltered systems serving at least 10,000 people must sample their source water for 

Cryptosporidium at least monthly for 24 months. 

(3)(i) Filtered systems serving fewer than 10,000 people must sample their source water for E. coli at 

least once every two weeks for 12 months. 

(ii) A filtered system serving fewer than 10,000 people may avoid E. coli monitoring if the system notifies 

the State that it will monitor for Cryptosporidium as described in paragraph (a)(4) of this section. The 

system must notify the State no later than 3 months prior to the date the system is otherwise required to 

start E. coli monitoring under §141.701(c). 

(4) Filtered systems serving fewer than 10,000 people must sample their source water for 

Cryptosporidium at least twice per month for 12 months or at least monthly for 24 months if they meet 

one of the following, based on monitoring conducted under paragraph (a)(3) of this section: 

(i) For systems using lake/reservoir sources, the annual mean E. coli concentration is greater than 10 E. 

coli /100 mL. 

(ii) For systems using flowing stream sources, the annual mean E. coli concentration is greater than 50 

E. coli /100 mL. 

(iii) The system does not conduct E. coli monitoring as described in paragraph (a)(3) of this section. 

(iv) Systems using ground water under the direct influence of surface water (GWUDI) must comply with 

the requirements of paragraph (a)(4) of this section based on the E. coli level that applies to the nearest 

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surface water body. If no surface water body is nearby, the system must comply based on the 

requirements that apply to systems using lake/reservoir sources. 

(5) For filtered systems serving fewer than 10,000 people, the State may approve monitoring for an 

indicator other than E. coli under paragraph (a)(3) of this section. The State also may approve an 

alternative to the E. coli concentration in paragraph (a)(4)(i), (ii) or (iv) of this section to trigger 

Cryptosporidium monitoring. This approval by the State must be provided to the system in writing and 

must include the basis for the State's determination that the alternative indicator and/or trigger level will 

provide a more accurate identification of whether a system will exceed the Bin 1 Cryptosporidium level in 

§141.710. 

(6) Unfiltered systems serving fewer than 10,000 people must sample their source water for 

Cryptosporidium at least twice per month for 12 months or at least monthly for 24 months. 

(7) Systems may sample more frequently than required under this section if the sampling frequency is 

evenly spaced throughout the monitoring period. 

(b) Second round of source water monitoring. Systems must conduct a second round of source water 

monitoring that meets the requirements for monitoring parameters, frequency, and duration described in 

paragraph (a) of this section, unless they meet the monitoring exemption criteria in paragraph (d) of this 

section. Systems must conduct this monitoring on the schedule in paragraph (c) of this section. 

(c) Monitoring schedule. Systems must begin the monitoring required in paragraphs (a) and (b) of this 

section no later than the month beginning with the date listed in this table: 

Source Water Monitoring Starting Dates Table 

aApplies only to filtered systems.

bApplies to filtered systems that meet the conditions of paragraph (a)(4) of this section and unfiltered 

systems. 

(d) Monitoring avoidance. (1) Filtered systems are not required to conduct source water monitoring 

under this subpart if the system will provide a total of at least 5.5-log of treatment for Cryptosporidium, 

equivalent to meeting the treatment requirements of Bin 4 in §141.711. 

(2) Unfiltered systems are not required to conduct source water monitoring under this subpart if the 

system will provide a total of at least 3-log Cryptosporidium inactivation, equivalent to meeting the 

treatment requirements for unfiltered systems with a mean Cryptosporidium concentration of greater 

than 0.01 oocysts/L in §141.712. 

(3) If a system chooses to provide the level of treatment in paragraph (d)(1) or (2) of this section, as 

applicable, rather than start source water monitoring, the system must notify the State in writing no later 

than the date the system is otherwise required to submit a sampling schedule for monitoring under 

§141.702. Alternatively, a system may choose to stop sampling at any point after it has initiated 

monitoring if it notifies the State in writing that it will provide this level of treatment. Systems must install 

and operate technologies to provide this level of treatment by the applicable treatment compliance date 

in §141.713. 

(e) Plants operating only part of the year. Systems with subpart H plants that operate for only part of the 

year must conduct source water monitoring in accordance with this subpart, but with the following 

modifications: 

(1) Systems must sample their source water only during the months that the plant operates unless the 

State specifies another monitoring period based on plant operating practices. 

(2) Systems with plants that operate less than six months per year and that monitor for Cryptosporidium 

must collect at least six Cryptosporidium samples per year during each of two years of monitoring. 

Samples must be evenly spaced throughout the period the plant operates. 

(f)(1) New sources. A system that begins using a new source of surface water or GWUDI after the 

system is required to begin monitoring under paragraph (c) of this section must monitor the new source 

on a schedule the State approves. Source water monitoring must meet the requirements of this subpart. 

The system must also meet the bin classification and Cryptosporidium treatment requirements of 

§§141.710 and 141.711 or §141.712, as applicable, for the new source on a schedule the State 

approves. 

(2) The requirements of §141.701(f) apply to subpart H systems that begin operation after the monitoring 

start date applicable to the system's size under paragraph (c) of this section. 

Systems that serve . . 

.

Must begin the first 

round of source water 

monitoring no later 

than the month 

beginning . . .

And must begin the 

second round of source 

water monitoring no later 

than the month 

beginning . . .

(1) At least 100,000 

people

(i) October 1, 2006 (ii) April 1, 2015.

(2) From 50,000 to 

99,999 people

(i) April 1, 2007 (ii) October 1, 2015.

(3) From 10,000 to 

49,999 people

(i) April 1, 2008 (ii) October 1, 2016.

(4) Fewer than 10,000 

and monitor for E. coli a

(i) October 1, 2008 (ii) October 1, 2017.

(5) Fewer than 10,000 

and monitor for 

Cryptosporidium b

(i) April 1, 2010 (ii) April 1, 2019.

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(3) The system must begin a second round of source water monitoring no later than 6 years following 

initial bin classification under §141.710 or determination of the mean Cryptosporidium level under 

§141.712, as applicable. 

(g) Failure to collect any source water sample required under this section in accordance with the 

sampling schedule, sampling location, analytical method, approved laboratory, and reporting 

requirements of §§141.702 through 141.706 is a monitoring violation. 

(h) Grandfathering monitoring data. Systems may use (grandfather) monitoring data collected prior to 

the applicable monitoring start date in paragraph (c) of this section to meet the initial source water 

monitoring requirements in paragraph (a) of this section. Grandfathered data may substitute for an 

equivalent number of months at the end of the monitoring period. All data submitted under this 

paragraph must meet the requirements in §141.707. 

§ 141.702 Sampling schedules. 

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(a) Systems required to conduct source water monitoring under §141.701 must submit a sampling 

schedule that specifies the calendar dates when the system will collect each required sample. 

(1) Systems must submit sampling schedules no later than 3 months prior to the applicable date listed in 

§141.701(c) for each round of required monitoring. 

(2)(i) Systems serving at least 10,000 people must submit their sampling schedule for the initial round of 

source water monitoring under §141.701(a) to EPA electronically at https://intranet.epa.gov/lt2/. 

(ii) If a system is unable to submit the sampling schedule electronically, the system may use an 

alternative approach for submitting the sampling schedule that EPA approves. 

(3) Systems serving fewer than 10,000 people must submit their sampling schedules for the initial round 

of source water monitoring §141.701(a) to the State. 

(4) Systems must submit sampling schedules for the second round of source water monitoring §141.701

(b) to the State. 

(5) If EPA or the State does not respond to a system regarding its sampling schedule, the system must 

sample at the reported schedule. 

(b) Systems must collect samples within two days before or two days after the dates indicated in their 

sampling schedule ( i.e. , within a five-day period around the schedule date) unless one of the conditions 

of paragraph (b)(1) or (2) of this section applies. 

(1) If an extreme condition or situation exists that may pose danger to the sample collector, or that 

cannot be avoided and causes the system to be unable to sample in the scheduled five-day period, the 

system must sample as close to the scheduled date as is feasible unless the State approves an 

alternative sampling date. The system must submit an explanation for the delayed sampling date to the 

State concurrent with the shipment of the sample to the laboratory. 

(2)(i) If a system is unable to report a valid analytical result for a scheduled sampling date due to 

equipment failure, loss of or damage to the sample, failure to comply with the analytical method 

requirements, including the quality control requirements in §141.704, or the failure of an approved 

laboratory to analyze the sample, then the system must collect a replacement sample. 

(ii) The system must collect the replacement sample not later than 21 days after receiving information 

that an analytical result cannot be reported for the scheduled date unless the system demonstrates that 

collecting a replacement sample within this time frame is not feasible or the State approves an 

alternative resampling date. The system must submit an explanation for the delayed sampling date to 

the State concurrent with the shipment of the sample to the laboratory. 

(c) Systems that fail to meet the criteria of paragraph (b) of this section for any source water sample 

required under §141.701 must revise their sampling schedules to add dates for collecting all missed 

samples. Systems must submit the revised schedule to the State for approval prior to when the system 

begins collecting the missed samples. 

§ 141.703 Sampling locations. 

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(a) Systems required to conduct source water monitoring under §141.701 must collect samples for each 

plant that treats a surface water or GWUDI source. Where multiple plants draw water from the same 

influent, such as the same pipe or intake, the State may approve one set of monitoring results to be 

used to satisfy the requirements of §141.701 for all plants. 

(b)(1) Systems must collect source water samples prior to chemical treatment, such as coagulants, 

oxidants and disinfectants, unless the system meets the condition of paragraph (b)(2) of this section. 

(2) The State may approve a system to collect a source water sample after chemical treatment. To grant 

this approval, the State must determine that collecting a sample prior to chemical treatment is not 

feasible for the system and that the chemical treatment is unlikely to have a significant adverse effect on 

the analysis of the sample. 

(c) Systems that recycle filter backwash water must collect source water samples prior to the point of 

filter backwash water addition. 

(d) Bank filtration. (1) Systems that receive Cryptosporidium treatment credit for bank filtration under 

§141.173(b) or §141.552(a), as applicable, must collect source water samples in the surface water prior 

to bank filtration. 

(2) Systems that use bank filtration as pretreatment to a filtration plant must collect source water 

samples from the well ( i.e. , after bank filtration). Use of bank filtration during monitoring must be 

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consistent with routine operational practice. Systems collecting samples after a bank filtration process 

may not receive treatment credit for the bank filtration under §141.717(c). 

(e) Multiple sources. Systems with plants that use multiple water sources, including multiple surface 

water sources and blended surface water and ground water sources, must collect samples as specified 

in paragraph (e)(1) or (2) of this section. The use of multiple sources during monitoring must be 

consistent with routine operational practice. 

(1) If a sampling tap is available where the sources are combined prior to treatment, systems must 

collect samples from the tap. 

(2) If a sampling tap where the sources are combined prior to treatment is not available, systems must 

collect samples at each source near the intake on the same day and must follow either paragraph (e)(2)

(i) or (ii) of this section for sample analysis. 

(i) Systems may composite samples from each source into one sample prior to analysis. The volume of 

sample from each source must be weighted according to the proportion of the source in the total plant 

flow at the time the sample is collected. 

(ii) Systems may analyze samples from each source separately and calculate a weighted average of the 

analysis results for each sampling date. The weighted average must be calculated by multiplying the 

analysis result for each source by the fraction the source contributed to total plant flow at the time the 

sample was collected and then summing these values. 

(f) Additional Requirements. Systems must submit a description of their sampling location(s) to the State 

at the same time as the sampling schedule required under §141.702. This description must address the 

position of the sampling location in relation to the system's water source(s) and treatment processes, 

including pretreatment, points of chemical treatment, and filter backwash recycle. If the State does not 

respond to a system regarding sampling location(s), the system must sample at the reported location(s). 

§ 141.704 Analytical methods. 

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(a) Cryptosporidium. Systems must analyze for Cryptosporidium using Method 1623: Cryptosporidium 

and Giardia in Water by Filtration/IMS/FA, 2005, United States Environmental Protection Agency, EPA–

815–R–05–002 or Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2005, United States 

Environmental Protection Agency, EPA–815–R–05–001, which are incorporated by reference, or 

alternative methods listed in appendix A to subpart C of this part. The Director of the Federal Register 

approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. You 

may obtain a copy of these methods online from http://www.epa.gov/safewater/disinfection/lt2 or from 

the United States Environmental Protection Agency, Office of Ground Water and Drinking Water, 1201 

Constitution Ave., NW., Washington, DC 20460 ( Telephone: 800–426–4791). You may inspect a copy 

at the Water Docket in the EPA Docket Center, 1301 Constitution Ave., NW., Washington, DC 

( Telephone: 202–566–2426) or at the National Archives and Records Administration (NARA). For 

information on the availability of this material at NARA, call 202–741–6030, or go to: 

http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html . 

(1) Systems must analyze at least a 10 L sample or a packed pellet volume of at least 2 mL as 

generated by the methods listed in paragraph (a) of this section. Systems unable to process a 10 L 

sample must analyze as much sample volume as can be filtered by two filters approved by EPA for the 

methods listed in paragraph (a) of this section, up to a packed pellet volume of at least 2 mL. 

(2)(i) Matrix spike (MS) samples, as required by the methods in paragraph (a) of this section, must be 

spiked and filtered by a laboratory approved for Cryptosporidium analysis under §141.705. 

(ii) If the volume of the MS sample is greater than 10 L, the system may filter all but 10 L of the MS 

sample in the field, and ship the filtered sample and the remaining 10 L of source water to the laboratory. 

In this case, the laboratory must spike the remaining 10 L of water and filter it through the filter used to 

collect the balance of the sample in the field. 

(3) Flow cytometer-counted spiking suspensions must be used for MS samples and ongoing precision 

and recovery (OPR) samples. 

(b) E. coli. System must use methods for enumeration of E. coli in source water approved in §136.3(a) of 

this chapter or alternative methods listed in appendix A to subpart C of this part. 

(1) The time from sample collection to initiation of analysis may not exceed 30 hours unless the system 

meets the condition of paragraph (b)(2) of this section. 

(2) The State may approve on a case-by-case basis the holding of an E. coli sample for up to 48 hours 

between sample collection and initiation of analysis if the State determines that analyzing an E. coli 

sample within 30 hours is not feasible. E. coli samples held between 30 to 48 hours must be analyzed by 

the Colilert reagent version of Standard Method 9223B as listed in §136.3(a) of this title. 

(3) Systems must maintain samples between 0 °C and 10 °C during storage and transit to the 

laboratory. 

(c) Turbidity. Systems must use methods for turbidity measurement approved in §141.74(a)(1). 

[71 FR 769, Jan. 5, 2006, as amended at 74 FR 30959, June 29, 2009] 

§ 141.705 Approved laboratories. 

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(a) Cryptosporidium. Systems must have Cryptosporidium samples analyzed by a laboratory that is 

approved under EPA's Laboratory Quality Assurance Evaluation Program for Analysis of 

Cryptosporidium in Water or a laboratory that has been certified for Cryptosporidium analysis by an 

equivalent State laboratory certification program. 

(b) E. coli. Any laboratory certified by the EPA, the National Environmental Laboratory Accreditation 

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Conference or the State for total coliform or fecal coliform analysis under §141.74 is approved for E. coli 

analysis under this subpart when the laboratory uses the same technique for E. coli that the laboratory 

uses for §141.74. 

(c) Turbidity. Measurements of turbidity must be made by a party approved by the State. 

§ 141.706 Reporting source water monitoring results. 

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(a) Systems must report results from the source water monitoring required under §141.701 no later than 

10 days after the end of the first month following the month when the sample is collected. 

(b)(1) All systems serving at least 10,000 people must report the results from the initial source water 

monitoring required under §141.701(a) to EPA electronically at https://intranet.epa.gov/lt2/. 

(2) If a system is unable to report monitoring results electronically, the system may use an alternative 

approach for reporting monitoring results that EPA approves. 

(c) Systems serving fewer than 10,000 people must report results from the initial source water 

monitoring required under §141.701(a) to the State. 

(d) All systems must report results from the second round of source water monitoring required under 

§141.701(b) to the State. 

(e) Systems must report the applicable information in paragraphs (e)(1) and (2) of this section for the 

source water monitoring required under §141.701. 

(1) Systems must report the following data elements for each Cryptosporidium analysis: 

(i) For matrix spike samples, systems must also report the sample volume spiked and estimated number 

of oocysts spiked. These data are not required for field samples. 

(ii) For samples in which less than 10 L is filtered or less than 100% of the sample volume is examined, 

systems must also report the number of filters used and the packed pellet volume. 

(iii) For samples in which less than 100% of sample volume is examined, systems must also report the 

volume of resuspended concentrate and volume of this resuspension processed through 

immunomagnetic separation. 

(2) Systems must report the following data elements for each E. coli analysis: 

1Systems serving fewer than 10,000 people that are not required to monitor for turbidity under §141.701 

are not required to report turbidity with their E. coli results. 

§ 141.707 Grandfathering previously collected data. 

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(a)(1) Systems may comply with the initial source water monitoring requirements of §141.701(a) by 

grandfathering sample results collected before the system is required to begin monitoring ( i.e. , 

previously collected data). To be grandfathered, the sample results and analysis must meet the criteria 

in this section and the State must approve. 

(2) A filtered system may grandfather Cryptosporidium samples to meet the requirements of §141.701(a) 

when the system does not have corresponding E. coli and turbidity samples. A system that grandfathers 

Cryptosporidium samples without E. coli and turbidity samples is not required to collect E. coli and 

turbidity samples when the system completes the requirements for Cryptosporidium monitoring under 

§141.701(a). 

(b) E. coli sample analysis. The analysis of E. coli samples must meet the analytical method and 

Data element.

1. PWS ID.

2. Facility ID.

3. Sample collection date.

4. Sample type (field or matrix spike).

5. Sample volume filtered (L), to nearest 1/4 L.

6. Was 100% of filtered volume examined.

7. Number of oocysts counted.

Data element.

1. PWS ID.

2. Facility ID.

3. Sample collection date.

4. Analytical method number.

5. Method type.

6. Source type (flowing stream, lake/reservoir, GWUDI).

7. E. coli /100 mL.

8. Turbidity.1

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approved laboratory requirements of §§141.704 through 141.705. 

(c) Cryptosporidium sample analysis. The analysis of Cryptosporidium samples must meet the criteria in 

this paragraph. 

(1) Laboratories analyzed Cryptosporidium samples using one of the analytical methods in paragraphs 

(c)(1)(i) through (vi) of this section, which are incorporated by reference. The Director of the Federal 

Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 

51. You may obtain a copy of these methods on-line from the United States Environmental Protection 

Agency, Office of Ground Water and Drinking Water, 1201 Constitution Ave, NW, Washington, DC 

20460 (Telephone: 800–426–4791). You may inspect a copy at the Water Docket in the EPA Docket 

Center, 1301 Constitution Ave., NW, Washington, DC, (Telephone: 202–566–2426) or at the National 

Archives and Records Administration (NARA). For information on the availability of this material at 

NARA, call 202–741–6030, or go to: http://www.archives.gov/federal_ register/code_of_federal_ 

regulations/ibr_locations.html. 

(i) Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 2005, United States 

Environmental Protection Agency, EPA–815–R–05–002. 

(ii) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2005, United States Environmental 

Protection Agency, EPA–815–R–05–001. 

(iii) Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 2001, United States 

Environmental Protection Agency, EPA–821–R–01–025. 

(iv) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2001, United States Environmental 

Protection Agency, EPA–821–-R–01–026. 

(v) Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 1999, United States 

Environmental Protection Agency, EPA–821–R–99–006. 

(vi) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 1999, United States Environmental 

Protection Agency, EPA–821–R–99–001. 

(2) For each Cryptosporidium sample, the laboratory analyzed at least 10 L of sample or at least 2 mL of 

packed pellet or as much volume as could be filtered by 2 filters that EPA approved for the methods 

listed in paragraph (c)(1) of this section. 

(d) Sampling location. The sampling location must meet the conditions in §141.703. 

(e) Sampling frequency. Cryptosporidium samples were collected no less frequently than each calendar 

month on a regular schedule, beginning no earlier than January 1999. Sample collection intervals may 

vary for the conditions specified in §141.702(b)(1) and (2) if the system provides documentation of the 

condition when reporting monitoring results. 

(1) The State may approve grandfathering of previously collected data where there are time gaps in the 

sampling frequency if the system conducts additional monitoring the State specifies to ensure that the 

data used to comply with the initial source water monitoring requirements of §141.701(a) are seasonally 

representative and unbiased. 

(2) Systems may grandfather previously collected data where the sampling frequency within each month 

varied. If the Cryptosporidium sampling frequency varied, systems must follow the monthly averaging 

procedure in §141.710(b)(5) or §141.712(a)(3), as applicable, when calculating the bin classification for 

filtered systems or the mean Cryptosporidium concentration for unfiltered systems. 

(f) Reporting monitoring results for grandfathering. Systems that request to grandfather previously 

collected monitoring results must report the following information by the applicable dates listed in this 

paragraph. Systems serving at least 10,000 people must report this information to EPA unless the State 

approves reporting to the State rather than EPA. Systems serving fewer than 10,000 people must report 

this information to the State. 

(1) Systems must report that they intend to submit previously collected monitoring results for 

grandfathering. This report must specify the number of previously collected results the system will 

submit, the dates of the first and last sample, and whether a system will conduct additional source water 

monitoring to meet the requirements of §141.701(a). Systems must report this information no later than 

the date the sampling schedule under §141.702 is required. 

(2) Systems must report previously collected monitoring results for grandfathering, along with the 

associated documentation listed in paragraphs (f)(2)(i) through (iv) of this section, no later than two 

months after the applicable date listed in §141.701(c). 

(i) For each sample result, systems must report the applicable data elements in §141.706. 

(ii) Systems must certify that the reported monitoring results include all results the system generated 

during the time period beginning with the first reported result and ending with the final reported result. 

This applies to samples that were collected from the sampling location specified for source water 

monitoring under this subpart, not spiked, and analyzed using the laboratory's routine process for the 

analytical methods listed in this section. 

(iii) Systems must certify that the samples were representative of a plant's source water(s) and the 

source water(s) have not changed. Systems must report a description of the sampling location(s), which 

must address the position of the sampling location in relation to the system's water source(s) and 

treatment processes, including points of chemical addition and filter backwash recycle. 

(iv) For Cryptosporidium samples, the laboratory or laboratories that analyzed the samples must provide 

a letter certifying that the quality control criteria specified in the methods listed in paragraph (c)(1) of this 

section were met for each sample batch associated with the reported results. Alternatively, the 

laboratory may provide bench sheets and sample examination report forms for each field, matrix spike, 

IPR, OPR, and method blank sample associated with the reported results. 

(g) If the State determines that a previously collected data set submitted for grandfathering was 

generated during source water conditions that were not normal for the system, such as a drought, the 

State may disapprove the data. Alternatively, the State may approve the previously collected data if the 

system reports additional source water monitoring data, as determined by the State, to ensure that the 

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data set used under §141.710 or §141.712 represents average source water conditions for the system. 

(h) If a system submits previously collected data that fully meet the number of samples required for initial 

source water monitoring under §141.701(a) and some of the data are rejected due to not meeting the 

requirements of this section, systems must conduct additional monitoring to replace rejected data on a 

schedule the State approves. Systems are not required to begin this additional monitoring until two 

months after notification that data have been rejected and additional monitoring is necessary. 

Disinfection Profiling and Benchmarking Requirements 

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§ 141.708 Requirements when making a significant change in disinfection practice. 

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(a) Following the completion of initial source water monitoring under §141.701(a), a system that plans to 

make a significant change to its disinfection practice, as defined in paragraph (b) of this section, must 

develop disinfection profiles and calculate disinfection benchmarks for Giardia lamblia and viruses as 

described in §141.709. Prior to changing the disinfection practice, the system must notify the State and 

must include in this notice the information in paragraphs (a)(1) through (3) of this section. 

(1) A completed disinfection profile and disinfection benchmark for Giardia lamblia and viruses as 

described in §141.709. 

(2) A description of the proposed change in disinfection practice. 

(3) An analysis of how the proposed change will affect the current level of disinfection. 

(b) Significant changes to disinfection practice are defined as follows: 

(1) Changes to the point of disinfection; 

(2) Changes to the disinfectant(s) used in the treatment plant; 

(3) Changes to the disinfection process; or 

(4) Any other modification identified by the State as a significant change to disinfection practice. 

§ 141.709 Developing the disinfection profile and benchmark. 

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(a) Systems required to develop disinfection profiles under §141.708 must follow the requirements of this 

section. Systems must monitor at least weekly for a period of 12 consecutive months to determine the 

total log inactivation for Giardia lamblia and viruses. If systems monitor more frequently, the monitoring 

frequency must be evenly spaced. Systems that operate for fewer than 12 months per year must monitor 

weekly during the period of operation. Systems must determine log inactivation for Giardia lamblia 

through the entire plant, based on CT99.9values in Tables 1.1 through 1.6, 2.1 and 3.1 of §141.74(b) as 

applicable. Systems must determine log inactivation for viruses through the entire treatment plant based 

on a protocol approved by the State. 

(b) Systems with a single point of disinfectant application prior to the entrance to the distribution system 

must conduct the monitoring in paragraphs (b)(1) through (4) of this section. Systems with more than 

one point of disinfectant application must conduct the monitoring in paragraphs (b)(1) through (4) of this 

section for each disinfection segment. Systems must monitor the parameters necessary to determine the 

total inactivation ratio, using analytical methods in §141.74(a). 

(1) For systems using a disinfectant other than UV, the temperature of the disinfected water must be 

measured at each residual disinfectant concentration sampling point during peak hourly flow or at an 

alternative location approved by the State. 

(2) For systems using chlorine, the pH of the disinfected water must be measured at each chlorine 

residual disinfectant concentration sampling point during peak hourly flow or at an alternative location 

approved by the State. 

(3) The disinfectant contact time(s) (t) must be determined during peak hourly flow. 

(4) The residual disinfectant concentration(s) (C) of the water before or at the first customer and prior to 

each additional point of disinfectant application must be measured during peak hourly flow. 

(c) In lieu of conducting new monitoring under paragraph (b) of this section, systems may elect to meet 

the requirements of paragraphs (c)(1) or (2) of this section. 

(1) Systems that have at least one year of existing data that are substantially equivalent to data collected 

under the provisions of paragraph (b) of this section may use these data to develop disinfection profiles 

as specified in this section if the system has neither made a significant change to its treatment practice 

nor changed sources since the data were collected. Systems may develop disinfection profiles using up 

to three years of existing data. 

(2) Systems may use disinfection profile(s) developed under §141.172 or §§141.530 through 141.536 in 

lieu of developing a new profile if the system has neither made a significant change to its treatment 

practice nor changed sources since the profile was developed. Systems that have not developed a virus 

profile under §141.172 or §§141.530 through 141.536 must develop a virus profile using the same 

monitoring data on which the Giardia lamblia profile is based. 

(d) Systems must calculate the total inactivation ratio for Giardia lamblia as specified in paragraphs (d)

(1) through (3) of this section. 

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(1) Systems using only one point of disinfectant application may determine the total inactivation ratio for 

the disinfection segment based on either of the methods in paragraph (d)(1)(i) or (ii) of this section. 

(i) Determine one inactivation ratio (CTcalc/CT99.9) before or at the first customer during peak hourly 

flow. 

(ii) Determine successive CTcalc/CT99.9values, representing sequential inactivation ratios, between the 

point of disinfectant application and a point before or at the first customer during peak hourly flow. The 

system must calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and 

then adding the (CTcalc/CT99.9) values together to determine (Σ (CTcalc/CT99.9)). 

(2) Systems using more than one point of disinfectant application before the first customer must 

determine the CT value of each disinfection segment immediately prior to the next point of disinfectant 

application, or for the final segment, before or at the first customer, during peak hourly flow. The 

(CTcalc/CT99.9) value of each segment and (Σ (CTcalc/CT99.9)) must be calculated using the method in 

paragraph (d)(1)(ii) of this section. 

(3) The system must determine the total logs of inactivation by multiplying the value calculated in 

paragraph (d)(1) or (d)(2) of this section by 3.0. 

(4) Systems must calculate the log of inactivation for viruses using a protocol approved by the State. 

(e) Systems must use the procedures specified in paragraphs (e)(1) and (2) of this section to calculate a 

disinfection benchmark. 

(1) For each year of profiling data collected and calculated under paragraphs (a) through (d) of this 

section, systems must determine the lowest mean monthly level of both Giardia lamblia and virus 

inactivation. Systems must determine the mean Giardia lamblia and virus inactivation for each calendar 

month for each year of profiling data by dividing the sum of daily or weekly Giardia lamblia and virus log 

inactivation by the number of values calculated for that month. 

(2) The disinfection benchmark is the lowest monthly mean value (for systems with one year of profiling 

data) or the mean of the lowest monthly mean values (for systems with more than one year of profiling 

data) of Giardia lamblia and virus log inactivation in each year of profiling data. 

Treatment Technique Requirements 

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§ 141.710 Bin classification for filtered systems. 

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(a) Following completion of the initial round of source water monitoring required under §141.701(a), 

filtered systems must calculate an initial Cryptosporidium bin concentration for each plant for which 

monitoring was required. Calculation of the bin concentration must use the Cryptosporidium results 

reported under §141.701(a) and must follow the procedures in paragraphs (b)(1) through (5) of this 

section. 

(b)(1) For systems that collect a total of at least 48 samples, the bin concentration is equal to the 

arithmetic mean of all sample concentrations. 

(2) For systems that collect a total of at least 24 samples, but not more than 47 samples, the bin 

concentration is equal to the highest arithmetic mean of all sample concentrations in any 12 consecutive 

months during which Cryptosporidium samples were collected. 

(3) For systems that serve fewer than 10,000 people and monitor for Cryptosporidium for only one year 

( i.e. , collect 24 samples in 12 months), the bin concentration is equal to the arithmetic mean of all 

sample concentrations. 

(4) For systems with plants operating only part of the year that monitor fewer than 12 months per year 

under §141.701(e), the bin concentration is equal to the highest arithmetic mean of all sample 

concentrations during any year of Cryptosporidium monitoring. 

(5) If the monthly Cryptosporidium sampling frequency varies, systems must first calculate a monthly 

average for each month of monitoring. Systems must then use these monthly average concentrations, 

rather than individual sample concentrations, in the applicable calculation for bin classification in 

paragraphs (b)(1) through (4) of this section. 

(c) Filtered systems must determine their initial bin classification from the following table and using the 

Cryptosporidium bin concentration calculated under paragraphs (a)–(b) of this section: 

Bin Classification Table for Filtered Systems 

For systems that are:

With a 

Cryptosporidium bin 

concentration of . . .1

The bin 

classification 

is . . .

. . . required to monitor for 

Cryptosporidium under §141.701

Cryptosporidium <0.075 

oocyst/L

Bin 1.

 0.075 oocysts/L 

≤Cryptosporidium <1.0 

oocysts/L

Bin 2.

 1.0 oocysts/L 

≤Cryptosporidium <3.0 

oocysts/L

Bin 3.

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1Based on calculations in paragraph (a) or (d) of this section, as applicable.

(d) Following completion of the second round of source water monitoring required under §141.701(b), 

filtered systems must recalculate their Cryptosporidium bin concentration using the Cryptosporidium 

results reported under §141.701(b) and following the procedures in paragraphs (b)(1) through (4) of this 

section. Systems must then redetermine their bin classification using this bin concentration and the table 

in paragraph (c) of this section. 

(e)(1) Filtered systems must report their initial bin classification under paragraph (c) of this section to the 

State for approval no later than 6 months after the system is required to complete initial source water 

monitoring based on the schedule in §141.701(c). 

(2) Systems must report their bin classification under paragraph (d) of this section to the State for 

approval no later than 6 months after the system is required to complete the second round of source 

water monitoring based on the schedule in §141.701(c). 

(3) The bin classification report to the State must include a summary of source water monitoring data 

and the calculation procedure used to determine bin classification. 

(f) Failure to comply with the conditions of paragraph (e) of this section is a violation of the treatment 

technique requirement. 

§ 141.711 Filtered system additional Cryptosporidium treatment requirements. 

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(a) Filtered systems must provide the level of additional treatment for Cryptosporidium specified in this 

paragraph based on their bin classification as determined under §141.710 and according to the 

schedule in §141.713. 

1As determined by the State such that the total Cryptosporidium removal and inactivation is at least 4.0-

log. 

2As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.0-

log. 

3As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.5-

log. 

(b)(1) Filtered systems must use one or more of the treatment and management options listed in 

§141.715, termed the microbial toolbox, to comply with the additional Cryptosporidium treatment 

required in paragraph (a) of this section. 

(2) Systems classified in Bin 3 and Bin 4 must achieve at least 1-log of the additional Cryptosporidium 

treatment required under paragraph (a) of this section using either one or a combination of the following: 

bag filters, bank filtration, cartridge filters, chlorine dioxide, membranes, ozone, or UV, as described in 

§§141.716 through 141.720. 

(c) Failure by a system in any month to achieve treatment credit by meeting criteria in §§141.716 

through 141.720 for microbial toolbox options that is at least equal to the level of treatment required in 

paragraph (a) of this section is a violation of the treatment technique requirement. 

(d) If the State determines during a sanitary survey or an equivalent source water assessment that after 

a system completed the monitoring conducted under §141.701(a) or §141.701(b), significant changes 

occurred in the system's watershed that could lead to increased contamination of the source water by 

Cryptosporidium, the system must take actions specified by the State to address the contamination. 

These actions may include additional source water monitoring and/or implementing microbial toolbox 

 Cryptosporidium ≥3.0 

oocysts/L

Bin 4.

. . . serving fewer than 10,000 

people and NOT required to 

monitor for Cryptosporidium under 

§141.701(a)(4)

NA Bin 1.

If the system 

bin 

classification 

is . . .

And the system uses the following filtration treatment in 

full compliance with subparts H, P, and T of this part (as 

applicable), then the additional Cryptosporidium

treatment requirements are . . .

Conventional 

filtration 

treatment 

(including 

softening)

Direct 

filtration

Slow sand or 

diatomaceous 

earth filtration

Alternative 

filtration 

technologies

Bin 1 No additional 

treatment

No 

additional 

treatment

No additional 

treatment

No additional 

treatment.

Bin 2 1-log treatment 1.5-log 

treatment

1-log treatment (

1)

Bin 3 2-log treatment 2.5-log 

treatment

2-log treatment (

2)

Bin 4 2.5-log 

treatment

3-log 

treatment

2.5-log treatment (

3)

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options listed in §141.715. 

§ 141.712 Unfiltered system Cryptosporidium treatment requirements. 

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(a) Determination of mean Cryptosporidium level. (1) Following completion of the initial source water 

monitoring required under §141.701(a), unfiltered systems must calculate the arithmetic mean of all 

Cryptosporidium sample concentrations reported under §141.701(a). Systems must report this value to 

the State for approval no later than 6 months after the month the system is required to complete initial 

source water monitoring based on the schedule in §141.701(c). 

(2) Following completion of the second round of source water monitoring required under §141.701(b), 

unfiltered systems must calculate the arithmetic mean of all Cryptosporidium sample concentrations 

reported under §141.701(b). Systems must report this value to the State for approval no later than 6 

months after the month the system is required to complete the second round of source water monitoring 

based on the schedule in §141.701(c). 

(3) If the monthly Cryptosporidium sampling frequency varies, systems must first calculate a monthly 

average for each month of monitoring. Systems must then use these monthly average concentrations, 

rather than individual sample concentrations, in the calculation of the mean Cryptosporidium level in 

paragraphs (a)(1) or (2) of this section. 

(4) The report to the State of the mean Cryptosporidium levels calculated under paragraphs (a)(1) and 

(2) of this section must include a summary of the source water monitoring data used for the calculation. 

(5) Failure to comply with the conditions of paragraph (a) of this section is a violation of the treatment 

technique requirement. 

(b) Cryptosporidium inactivation requirements. Unfiltered systems must provide the level of inactivation 

for Cryptosporidium specified in this paragraph, based on their mean Cryptosporidium levels as 

determined under paragraph (a) of this section and according to the schedule in §141.713. 

(1) Unfiltered systems with a mean Cryptosporidium level of 0.01 oocysts/L or less must provide at least 

2-log Cryptosporidium inactivation. 

(2) Unfiltered systems with a mean Cryptosporidium level of greater than 0.01 oocysts/L must provide at 

least 3-log Cryptosporidium inactivation. 

(c) Inactivation treatment technology requirements. Unfiltered systems must use chlorine dioxide, ozone, 

or UV as described in §141.720 to meet the Cryptosporidium inactivation requirements of this section. 

(1) Systems that use chlorine dioxide or ozone and fail to achieve the Cryptosporidium inactivation 

required in paragraph (b) of this section on more than one day in the calendar month are in violation of 

the treatment technique requirement. 

(2) Systems that use UV light and fail to achieve the Cryptosporidium inactivation required in paragraph 

(b) of this section by meeting the criteria in §141.720(d)(3)(ii) are in violation of the treatment technique 

requirement. 

(d) Use of two disinfectants. Unfiltered systems must meet the combined Cryptosporidium inactivation 

requirements of this section and Giardia lamblia and virus inactivation requirements of §141.72(a) using 

a minimum of two disinfectants, and each of two disinfectants must separately achieve the total 

inactivation required for either Cryptosporidium, Giardia lamblia, or viruses. 

§ 141.713 Schedule for compliance with Cryptosporidium treatment requirements. 

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(a) Following initial bin classification under §141.710(c), filtered systems must provide the level of 

treatment for Cryptosporidium required under §141.711 according to the schedule in paragraph (c) of 

this section. 

(b) Following initial determination of the mean Cryptosporidium level under §141.712(a)(1), unfiltered 

systems must provide the level of treatment for Cryptosporidium required under §141.712 according to 

the schedule in paragraph (c) of this section. 

(c) Cryptosporidium treatment compliance dates. 

Cryptosporidium Treatment Compliance Dates Table 

aStates may allow up to an additional two years for complying with the treatment requirement for 

systems making capital improvements. 

(d) If the bin classification for a filtered system changes following the second round of source water 

Systems that serve . 

. .

Must comply with Cryptosporidium treatment 

requirements no later than . . .a

(1) At least 100,000 

people

(i) April 1, 2012.

(2) From 50,000 to 

99,999 people

(i) October 1, 2012.

(3) From 10,000 to 

49,999 people

(i) October 1, 2013.

(4) Fewer than 10,000 

people

(i) October 1, 2014.

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monitoring, as determined under §141.710(d), the system must provide the level of treatment for 

Cryptosporidium required under §141.711 on a schedule the State approves. 

(e) If the mean Cryptosporidium level for an unfiltered system changes following the second round of 

monitoring, as determined under §141.712(a)(2), and if the system must provide a different level of 

Cryptosporidium treatment under §141.712 due to this change, the system must meet this treatment 

requirement on a schedule the State approves. 

§ 141.714 Requirements for uncovered finished water storage facilities. 

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(a) Systems using uncovered finished water storage facilities must comply with the conditions of this 

section. 

(b) Systems must notify the State of the use of each uncovered finished water storage facility no later 

than April 1, 2008. 

(c) Systems must meet the conditions of paragraph (c)(1) or (2) of this section for each uncovered 

finished water storage facility or be in compliance with a State-approved schedule to meet these 

conditions no later than April 1, 2009. 

(1) Systems must cover any uncovered finished water storage facility. 

(2) Systems must treat the discharge from the uncovered finished water storage facility to the distribution 

system to achieve inactivation and/or removal of at least 4-log virus, 3-log Giardia lamblia, and 2-log 

Cryptosporidium using a protocol approved by the State. 

(d) Failure to comply with the requirements of this section is a violation of the treatment technique 

requirement. 

Requirements for Microbial Toolbox Components 

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§ 141.715 Microbial toolbox options for meeting Cryptosporidium treatment 

requirements. 

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(a)(1) Systems receive the treatment credits listed in the table in paragraph (b) of this section by meeting 

the conditions for microbial toolbox options described in §§141.716 through 141.720. Systems apply 

these treatment credits to meet the treatment requirements in §141.711 or §141.712, as applicable. 

(2) Unfiltered systems are eligible for treatment credits for the microbial toolbox options described in 

§141.720 only. 

(b) The following table summarizes options in the microbial toolbox: 

Microbial Toolbox Summary Table: Options, Treatment Credits and Criteria 

Toolbox Option

Cryptosporidium treatment credit with design and 

implementation criteria

Source Protection and Management Toolbox Options

(1) Watershed 

control program

0.5-log credit for State-approved program comprising 

required elements, annual program status report to 

State, and regular watershed survey. Unfiltered systems 

are not eligible for credit. Specific criteria are in 

§141.716(a).

(2) Alternative 

source/intake 

management

No prescribed credit. Systems may conduct 

simultaneous monitoring for treatment bin classification 

at alternative intake locations or under alternative intake 

management strategies. Specific criteria are in §141.716

(b).

Pre Filtration Toolbox Options

(3) 

Presedimentation 

basin with 

coagulation

0.5-log credit during any month that presedimentation 

basins achieve a monthly mean reduction of 0.5-log or 

greater in turbidity or alternative State-approved 

performance criteria. To be eligible, basins must be 

operated continuously with coagulant addition and all 

plant flow must pass through basins. Specific criteria are 

in §141.717(a).

(4) Two-stage lime 

softening

0.5-log credit for two-stage softening where chemical 

addition and hardness precipitation occur in both stages. 

All plant flow must pass through both stages. Singlestage softening is credited as equivalent to conventional 

treatment. Specific criteria are in §141.717(b).

(5) Bank filtration 0.5-log credit for 25-foot setback; 1.0-log credit for 50-

foot setback; aquifer must be unconsolidated sand 

containing at least 10 percent fines; average turbidity in 

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§ 141.716 Source toolbox components. 

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(a) Watershed control program. Systems receive 0.5-log Cryptosporidium treatment credit for 

implementing a watershed control program that meets the requirements of this section. 

(1) Systems that intend to apply for the watershed control program credit must notify the State of this 

intent no later than two years prior to the treatment compliance date applicable to the system in 

§141.713. 

(2) Systems must submit to the State a proposed watershed control plan no later than one year before 

the applicable treatment compliance date in §141.713. The State must approve the watershed control 

plan for the system to receive watershed control program treatment credit. The watershed control plan 

must include the elements in paragraphs (a)(2)(i) through (iv) of this section. 

(i) Identification of an “area of influence” outside of which the likelihood of Cryptosporidium or fecal 

contamination affecting the treatment plant intake is not significant. This is the area to be evaluated in 

future watershed surveys under paragraph (a)(5)(ii) of this section. 

(ii) Identification of both potential and actual sources of Cryptosporidium contamination and an 

assessment of the relative impact of these sources on the system's source water quality. 

(iii) An analysis of the effectiveness and feasibility of control measures that could reduce 

Cryptosporidium loading from sources of contamination to the system's source water. 

(iv) A statement of goals and specific actions the system will undertake to reduce source water 

Cryptosporidium levels. The plan must explain how the actions are expected to contribute to specific 

goals, identify watershed partners and their roles, identify resource requirements and commitments, and 

include a schedule for plan implementation with deadlines for completing specific actions identified in the 

plan. 

wells must be less than 1 NTU. Systems using wells 

followed by filtration when conducting source water 

monitoring must sample the well to determine bin 

classification and are not eligible for additional credit. 

Specific criteria are in §141.717(c).

Treatment Performance Toolbox Options

(6) Combined filter 

performance

0.5-log credit for combined filter effluent turbidity less 

than or equal to 0.15 NTU in at least 95 percent of 

measurements each month. Specific criteria are in 

§141.718(a).

(7) Individual filter 

performance

0.5-log credit (in addition to 0.5-log combined filter 

performance credit) if individual filter effluent turbidity is 

less than or equal to 0.15 NTU in at least 95 percent of 

samples each month in each filter and is never greater 

than 0.3 NTU in two consecutive measurements in any 

filter. Specific criteria are in §141.718(b).

(8) Demonstration 

of performance

Credit awarded to unit process or treatment train based 

on a demonstration to the State with a State- approved 

protocol. Specific criteria are in §141.718(c).

Additional Filtration Toolbox Options

(9) Bag or cartridge 

filters (individual 

filters)

Up to 2-log credit based on the removal efficiency 

demonstrated during challenge testing with a 1.0-log 

factor of safety. Specific criteria are in §141.719(a).

(10) Bag or 

cartridge filters (in 

series)

Up to 2.5-log credit based on the removal efficiency 

demonstrated during challenge testing with a 0.5-log 

factor of safety. Specific criteria are in §141.719(a).

(11) Membrane 

filtration

Log credit equivalent to removal efficiency demonstrated 

in challenge test for device if supported by direct 

integrity testing. Specific criteria are in §141.719(b).

(12) Second stage 

filtration

0.5-log credit for second separate granular media 

filtration stage if treatment train includes coagulation 

prior to first filter. Specific criteria are in §141.719(c)

(13) Slow sand 

filters

2.5-log credit as a secondary filtration step; 3.0-log 

credit as a primary filtration process. No prior 

chlorination for either option. Specific criteria are in 

§141.719(d).

Inactivation Toolbox Options

(14) Chlorine 

dioxide

Log credit based on measured CT in relation to CT 

table. Specific criteria in §141.720(b)

(15) Ozone Log credit based on measured CT in relation to CT 

table. Specific criteria in §141.720(b).

(16) UV Log credit based on validated UV dose in relation to UV 

dose table; reactor validation testing required to 

establish UV dose and associated operating conditions. 

Specific criteria in §141.720(d).

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(3) Systems with existing watershed control programs ( i.e., programs in place on January 5, 2006) are 

eligible to seek this credit. Their watershed control plans must meet the criteria in paragraph (a)(2) of 

this section and must specify ongoing and future actions that will reduce source water Cryptosporidium 

levels. 

(4) If the State does not respond to a system regarding approval of a watershed control plan submitted 

under this section and the system meets the other requirements of this section, the watershed control 

program will be considered approved and 0.5 log Cryptosporidium treatment credit will be awarded 

unless and until the State subsequently withdraws such approval. 

(5) Systems must complete the actions in paragraphs (a)(5)(i) through (iii) of this section to maintain the 

0.5-log credit. 

(i) Submit an annual watershed control program status report to the State. The annual watershed control 

program status report must describe the system's implementation of the approved plan and assess the 

adequacy of the plan to meet its goals. It must explain how the system is addressing any shortcomings 

in plan implementation, including those previously identified by the State or as the result of the 

watershed survey conducted under paragraph (a)(5)(ii) of this section. It must also describe any 

significant changes that have occurred in the watershed since the last watershed sanitary survey. If a 

system determines during implementation that making a significant change to its approved watershed 

control program is necessary, the system must notify the State prior to making any such changes. If any 

change is likely to reduce the level of source water protection, the system must also list in its notification 

the actions the system will take to mitigate this effect. 

(ii) Undergo a watershed sanitary survey every three years for community water systems and every five 

years for noncommunity water systems and submit the survey report to the State. The survey must be 

conducted according to State guidelines and by persons the State approves. 

(A) The watershed sanitary survey must meet the following criteria: encompass the region identified in 

the State-approved watershed control plan as the area of influence; assess the implementation of 

actions to reduce source water Cryptosporidium levels; and identify any significant new sources of 

Cryptosporidium. 

(B) If the State determines that significant changes may have occurred in the watershed since the 

previous watershed sanitary survey, systems must undergo another watershed sanitary survey by a date 

the State requires, which may be earlier than the regular date in paragraph (a)(5)(ii) of this section. 

(iii) The system must make the watershed control plan, annual status reports, and watershed sanitary 

survey reports available to the public upon request. These documents must be in a plain language style 

and include criteria by which to evaluate the success of the program in achieving plan goals. The State 

may approve systems to withhold from the public portions of the annual status report, watershed control 

plan, and watershed sanitary survey based on water supply security considerations. 

(6) If the State determines that a system is not carrying out the approved watershed control plan, the 

State may withdraw the watershed control program treatment credit. 

(b) Alternative source. (1) A system may conduct source water monitoring that reflects a different intake 

location (either in the same source or for an alternate source) or a different procedure for the timing or 

level of withdrawal from the source (alternative source monitoring). If the State approves, a system may 

determine its bin classification under §141.710 based on the alternative source monitoring results. 

(2) If systems conduct alternative source monitoring under paragraph (b)(1) of this section, systems 

must also monitor their current plant intake concurrently as described in §141.701. 

(3) Alternative source monitoring under paragraph (b)(1) of this section must meet the requirements for 

source monitoring to determine bin classification, as described in §§141.701 through 141.706. Systems 

must report the alternative source monitoring results to the State, along with supporting information 

documenting the operating conditions under which the samples were collected. 

(4) If a system determines its bin classification under §141.710 using alternative source monitoring 

results that reflect a different intake location or a different procedure for managing the timing or level of 

withdrawal from the source, the system must relocate the intake or permanently adopt the withdrawal 

procedure, as applicable, no later than the applicable treatment compliance date in §141.713. 

§ 141.717 Pre-filtration treatment toolbox components. 

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(a) Presedimentation. Systems receive 0.5-log Cryptosporidium treatment credit for a presedimentation 

basin during any month the process meets the criteria in this paragraph. 

(1) The presedimentation basin must be in continuous operation and must treat the entire plant flow 

taken from a surface water or GWUDI source. 

(2) The system must continuously add a coagulant to the presedimentation basin. 

(3) The presedimentation basin must achieve the performance criteria in paragraph (3)(i) or (ii) of this 

section. 

(i) Demonstrates at least 0.5-log mean reduction of influent turbidity. This reduction must be determined 

using daily turbidity measurements in the presedimentation process influent and effluent and must be 

calculated as follows: log10(monthly mean of daily influent turbidity)−log10(monthly mean of daily effluent 

turbidity). 

(ii) Complies with State-approved performance criteria that demonstrate at least 0.5-log mean removal of 

micron-sized particulate material through the presedimentation process. 

(b) Two-stage lime softening. Systems receive an additional 0.5-log Cryptosporidium treatment credit for 

a two-stage lime softening plant if chemical addition and hardness precipitation occur in two separate 

and sequential softening stages prior to filtration. Both softening stages must treat the entire plant flow 

taken from a surface water or GWUDI source. 

(c) Bank filtration. Systems receive Cryptosporidium treatment credit for bank filtration that serves as 

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pretreatment to a filtration plant by meeting the criteria in this paragraph. Systems using bank filtration 

when they begin source water monitoring under §141.701(a) must collect samples as described in 

§141.703(d) and are not eligible for this credit. 

(1) Wells with a ground water flow path of at least 25 feet receive 0.5-log treatment credit; wells with a 

ground water flow path of at least 50 feet receive 1.0-log treatment credit. The ground water flow path 

must be determined as specified in paragraph (c)(4) of this section. 

(2) Only wells in granular aquifers are eligible for treatment credit. Granular aquifers are those 

comprised of sand, clay, silt, rock fragments, pebbles or larger particles, and minor cement. A system 

must characterize the aquifer at the well site to determine aquifer properties. Systems must extract a 

core from the aquifer and demonstrate that in at least 90 percent of the core length, grains less than 1.0 

mm in diameter constitute at least 10 percent of the core material. 

(3) Only horizontal and vertical wells are eligible for treatment credit. 

(4) For vertical wells, the ground water flow path is the measured distance from the edge of the surface 

water body under high flow conditions (determined by the 100 year floodplain elevation boundary or by 

the floodway, as defined in Federal Emergency Management Agency flood hazard maps) to the well 

screen. For horizontal wells, the ground water flow path is the measured distance from the bed of the 

river under normal flow conditions to the closest horizontal well lateral screen. 

(5) Systems must monitor each wellhead for turbidity at least once every four hours while the bank 

filtration process is in operation. If monthly average turbidity levels, based on daily maximum values in 

the well, exceed 1 NTU, the system must report this result to the State and conduct an assessment 

within 30 days to determine the cause of the high turbidity levels in the well. If the State determines that 

microbial removal has been compromised, the State may revoke treatment credit until the system 

implements corrective actions approved by the State to remediate the problem. 

(6) Springs and infiltration galleries are not eligible for treatment credit under this section, but are eligible 

for credit under §141.718(c). 

(7) Bank filtration demonstration of performance. The State may approve Cryptosporidium treatment 

credit for bank filtration based on a demonstration of performance study that meets the criteria in this 

paragraph. This treatment credit may be greater than 1.0-log and may be awarded to bank filtration that 

does not meet the criteria in paragraphs (c)(1)–(5) of this section. 

(i) The study must follow a State-approved protocol and must involve the collection of data on the 

removal of Cryptosporidium or a surrogate for Cryptosporidium and related hydrogeologic and water 

quality parameters during the full range of operating conditions. 

(ii) The study must include sampling both from the production well(s) and from monitoring wells that are 

screened and located along the shortest flow path between the surface water source and the production 

well(s). 

§ 141.718 Treatment performance toolbox components. 

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(a) Combined filter performance. Systems using conventional filtration treatment or direct filtration 

treatment receive an additional 0.5-log Cryptosporidium treatment credit during any month the system 

meets the criteria in this paragraph. Combined filter effluent (CFE) turbidity must be less than or equal to 

0.15 NTU in at least 95 percent of the measurements. Turbidity must be measured as described in 

§141.74(a) and (c). 

(b) Individual filter performance. Systems using conventional filtration treatment or direct filtration 

treatment receive 0.5-log Cryptosporidium treatment credit, which can be in addition to the 0.5-log credit 

under paragraph (a) of this section, during any month the system meets the criteria in this paragraph. 

Compliance with these criteria must be based on individual filter turbidity monitoring as described in 

§141.174 or §141.560, as applicable. 

(1) The filtered water turbidity for each individual filter must be less than or equal to 0.15 NTU in at least 

95 percent of the measurements recorded each month. 

(2) No individual filter may have a measured turbidity greater than 0.3 NTU in two consecutive 

measurements taken 15 minutes apart. 

(3) Any system that has received treatment credit for individual filter performance and fails to meet the 

requirements of paragraph (b)(1) or (2) of this section during any month does not receive a treatment 

technique violation under §141.711(c) if the State determines the following: 

(i) The failure was due to unusual and short-term circumstances that could not reasonably be prevented 

through optimizing treatment plant design, operation, and maintenance. 

(ii) The system has experienced no more than two such failures in any calendar year. 

(c) Demonstration of performance. The State may approve Cryptosporidium treatment credit for drinking 

water treatment processes based on a demonstration of performance study that meets the criteria in this 

paragraph. This treatment credit may be greater than or less than the prescribed treatment credits in 

§141.711 or §§141.717 through 141.720 and may be awarded to treatment processes that do not meet 

the criteria for the prescribed credits. 

(1) Systems cannot receive the prescribed treatment credit for any toolbox box option in §§141.717 

through 141.720 if that toolbox option is included in a demonstration of performance study for which 

treatment credit is awarded under this paragraph. 

(2) The demonstration of performance study must follow a State-approved protocol and must 

demonstrate the level of Cryptosporidium reduction the treatment process will achieve under the full 

range of expected operating conditions for the system. 

(3) Approval by the State must be in writing and may include monitoring and treatment performance 

criteria that the system must demonstrate and report on an ongoing basis to remain eligible for the 

treatment credit. The State may designate such criteria where necessary to verify that the conditions 

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under which the demonstration of performance credit was approved are maintained during routine 

operation. 

§ 141.719 Additional filtration toolbox components. 

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(a) Bag and cartridge filters. Systems receive Cryptosporidium treatment credit of up to 2.0-log for 

individual bag or cartridge filters and up to 2.5-log for bag or cartridge filters operated in series by 

meeting the criteria in paragraphs (a)(1) through (10) of this section. To be eligible for this credit, 

systems must report the results of challenge testing that meets the requirements of paragraphs (a)(2) 

through (9) of this section to the State. The filters must treat the entire plant flow taken from a subpart H 

source. 

(1) The Cryptosporidium treatment credit awarded to bag or cartridge filters must be based on the 

removal efficiency demonstrated during challenge testing that is conducted according to the criteria in 

paragraphs (a)(2) through (a)(9) of this section. A factor of safety equal to 1-log for individual bag or 

cartridge filters and 0.5-log for bag or cartridge filters in series must be applied to challenge testing 

results to determine removal credit. Systems may use results from challenge testing conducted prior to 

January 5, 2006 if the prior testing was consistent with the criteria specified in paragraphs (a)(2) through 

(9) of this section. 

(2) Challenge testing must be performed on full-scale bag or cartridge filters, and the associated filter 

housing or pressure vessel, that are identical in material and construction to the filters and housings the 

system will use for removal of Cryptosporidium. Bag or cartridge filters must be challenge tested in the 

same configuration that the system will use, either as individual filters or as a series configuration of 

filters. 

(3) Challenge testing must be conducted using Cryptosporidium or a surrogate that is removed no more 

efficiently than Cryptosporidium. The microorganism or surrogate used during challenge testing is 

referred to as the challenge particulate. The concentration of the challenge particulate must be 

determined using a method capable of discreetly quantifying the specific microorganism or surrogate 

used in the test; gross measurements such as turbidity may not be used. 

(4) The maximum feed water concentration that can be used during a challenge test must be based on 

the detection limit of the challenge particulate in the filtrate ( i.e. , filtrate detection limit) and must be 

calculated using the following equation: 

Maximum Feed Concentration = 1 × 104 × (Filtrate Detection Limit)

(5) Challenge testing must be conducted at the maximum design flow rate for the filter as specified by 

the manufacturer. 

(6) Each filter evaluated must be tested for a duration sufficient to reach 100 percent of the terminal 

pressure drop, which establishes the maximum pressure drop under which the filter may be used to 

comply with the requirements of this subpart. 

(7) Removal efficiency of a filter must be determined from the results of the challenge test and 

expressed in terms of log removal values using the following equation: 

LRV = LOG10(Cf

)−LOG10(Cp)

Where: 

LRV = log removal value demonstrated during challenge testing; Cf

= the feed concentration 

measured during the challenge test; and Cp= the filtrate concentration measured during the 

challenge test. In applying this equation, the same units must be used for the feed and filtrate 

concentrations. If the challenge particulate is not detected in the filtrate, then the term Cpmust 

be set equal to the detection limit. 

(8) Each filter tested must be challenged with the challenge particulate during three periods over the 

filtration cycle: within two hours of start-up of a new filter; when the pressure drop is between 45 and 55 

percent of the terminal pressure drop; and at the end of the cycle after the pressure drop has reached 

100 percent of the terminal pressure drop. An LRV must be calculated for each of these challenge 

periods for each filter tested. The LRV for the filter (LRVfilter) must be assigned the value of the minimum 

LRV observed during the three challenge periods for that filter. 

(9) If fewer than 20 filters are tested, the overall removal efficiency for the filter product line must be set 

equal to the lowest LRVfilteramong the filters tested. If 20 or more filters are tested, the overall removal 

efficiency for the filter product line must be set equal to the 10th percentile of the set of LRVfiltervalues 

for the various filters tested. The percentile is defined by (i/(n+1)) where i is the rank of n individual data 

points ordered lowest to highest. If necessary, the 10th percentile may be calculated using linear 

interpolation. 

(10) If a previously tested filter is modified in a manner that could change the removal efficiency of the 

filter product line, challenge testing to demonstrate the removal efficiency of the modified filter must be 

conducted and submitted to the State. 

(b) Membrane filtration. (1) Systems receive Cryptosporidium treatment credit for membrane filtration 

that meets the criteria of this paragraph. Membrane cartridge filters that meet the definition of membrane 

filtration in §141.2 are eligible for this credit. The level of treatment credit a system receives is equal to 

the lower of the values determined under paragraph (b)(1)(i) and (ii) of this section. 

(i) The removal efficiency demonstrated during challenge testing conducted under the conditions in 

paragraph (b)(2) of this section. 

(ii) The maximum removal efficiency that can be verified through direct integrity testing used with the 

membrane filtration process under the conditions in paragraph (b)(3) of this section. 

(2) Challenge testing. The membrane used by the system must undergo challenge testing to evaluate 

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removal efficiency, and the system must report the results of challenge testing to the State. Challenge 

testing must be conducted according to the criteria in paragraphs (b)(2)(i) through (vii) of this section. 

Systems may use data from challenge testing conducted prior to January 5, 2006 if the prior testing was 

consistent with the criteria in paragraphs (b)(2)(i) through (vii) of this section. 

(i) Challenge testing must be conducted on either a full-scale membrane module, identical in material 

and construction to the membrane modules used in the system's treatment facility, or a smaller-scale 

membrane module, identical in material and similar in construction to the full-scale module. A module is 

defined as the smallest component of a membrane unit in which a specific membrane surface area is 

housed in a device with a filtrate outlet structure. 

(ii) Challenge testing must be conducted using Cryptosporidium oocysts or a surrogate that is removed 

no more efficiently than Cryptosporidium oocysts. The organism or surrogate used during challenge 

testing is referred to as the challenge particulate. The concentration of the challenge particulate, in both 

the feed and filtrate water, must be determined using a method capable of discretely quantifying the 

specific challenge particulate used in the test; gross measurements such as turbidity may not be used. 

(iii) The maximum feed water concentration that can be used during a challenge test is based on the 

detection limit of the challenge particulate in the filtrate and must be determined according to the 

following equation: 

Maximum Feed Concentration = 3.16 × 106 × (Filtrate Detection Limit)

(iv) Challenge testing must be conducted under representative hydraulic conditions at the maximum 

design flux and maximum design process recovery specified by the manufacturer for the membrane 

module. Flux is defined as the throughput of a pressure driven membrane process expressed as flow 

per unit of membrane area. Recovery is defined as the volumetric percent of feed water that is converted 

to filtrate over the course of an operating cycle uninterrupted by events such as chemical cleaning or a 

solids removal process ( i.e. , backwashing). 

(v) Removal efficiency of a membrane module must be calculated from the challenge test results and 

expressed as a log removal value according to the following equation: 

LRV = LOG10(Cf

) − LOG10(Cp)

Where: 

LRV = log removal value demonstrated during the challenge test; Cf

= the feed concentration 

measured during the challenge test; and Cp= the filtrate concentration measured during the 

challenge test. Equivalent units must be used for the feed and filtrate concentrations. If the 

challenge particulate is not detected in the filtrate, the term Cpis set equal to the detection limit 

for the purpose of calculating the LRV. An LRV must be calculated for each membrane 

module evaluated during the challenge test. 

(vi) The removal efficiency of a membrane filtration process demonstrated during challenge testing must 

be expressed as a log removal value (LRVC-Test). If fewer than 20 modules are tested, then LRVCTestis equal to the lowest of the representative LRVs among the modules tested. If 20 or more modules 

are tested, then LRVC-Testis equal to the 10th percentile of the representative LRVs among the 

modules tested. The percentile is defined by (i/(n+1)) where i is the rank of n individual data points 

ordered lowest to highest. If necessary, the 10th percentile may be calculated using linear interpolation. 

(vii) The challenge test must establish a quality control release value (QCRV) for a non-destructive 

performance test that demonstrates the Cryptosporidium removal capability of the membrane filtration 

module. This performance test must be applied to each production membrane module used by the 

system that was not directly challenge tested in order to verify Cryptosporidium removal capability. 

Production modules that do not meet the established QCRV are not eligible for the treatment credit 

demonstrated during the challenge test. 

(viii) If a previously tested membrane is modified in a manner that could change the removal efficiency of 

the membrane or the applicability of the non-destructive performance test and associated QCRV, 

additional challenge testing to demonstrate the removal efficiency of, and determine a new QCRV for, 

the modified membrane must be conducted and submitted to the State. 

(3) Direct integrity testing. Systems must conduct direct integrity testing in a manner that demonstrates a 

removal efficiency equal to or greater than the removal credit awarded to the membrane filtration 

process and meets the requirements described in paragraphs (b)(3)(i) through (vi) of this section. A 

direct integrity test is defined as a physical test applied to a membrane unit in order to identify and 

isolate integrity breaches ( i.e. , one or more leaks that could result in contamination of the filtrate). 

(i) The direct integrity test must be independently applied to each membrane unit in service. A 

membrane unit is defined as a group of membrane modules that share common valving that allows the 

unit to be isolated from the rest of the system for the purpose of integrity testing or other maintenance. 

(ii) The direct integrity method must have a resolution of 3 micrometers or less, where resolution is 

defined as the size of the smallest integrity breach that contributes to a response from the direct integrity 

test. 

(iii) The direct integrity test must have a sensitivity sufficient to verify the log treatment credit awarded to 

the membrane filtration process by the State, where sensitivity is defined as the maximum log removal 

value that can be reliably verified by a direct integrity test. Sensitivity must be determined using the 

approach in either paragraph (b)(3)(iii)(A) or (B) of this section as applicable to the type of direct integrity 

test the system uses. 

(A) For direct integrity tests that use an applied pressure or vacuum, the direct integrity test sensitivity 

must be calculated according to the following equation: 

LRVDIT= LOG10(Qp/(VCF × Qbreach))

Where: 

LRVDIT= the sensitivity of the direct integrity test; Qp= total design filtrate flow from the 

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membrane unit; Qbreach= flow of water from an integrity breach associated with the smallest 

integrity test response that can be reliably measured, and VCF = volumetric concentration 

factor. The volumetric concentration factor is the ratio of the suspended solids concentration 

on the high pressure side of the membrane relative to that in the feed water. 

(B) For direct integrity tests that use a particulate or molecular marker, the direct integrity test sensitivity 

must be calculated according to the following equation: 

LRVDIT= LOG10(Cf

)−LOG10(Cp)

Where: 

LRVDIT= the sensitivity of the direct integrity test; Cf

= the typical feed concentration of the 

marker used in the test; and Cp= the filtrate concentration of the marker from an integral 

membrane unit. 

(iv) Systems must establish a control limit within the sensitivity limits of the direct integrity test that is 

indicative of an integral membrane unit capable of meeting the removal credit awarded by the State. 

(v) If the result of a direct integrity test exceeds the control limit established under paragraph (b)(3)(iv) of 

this section, the system must remove the membrane unit from service. Systems must conduct a direct 

integrity test to verify any repairs, and may return the membrane unit to service only if the direct integrity 

test is within the established control limit. 

(vi) Systems must conduct direct integrity testing on each membrane unit at a frequency of not less than 

once each day that the membrane unit is in operation. The State may approve less frequent testing, 

based on demonstrated process reliability, the use of multiple barriers effective for Cryptosporidium , or 

reliable process safeguards. 

(4) Indirect integrity monitoring. Systems must conduct continuous indirect integrity monitoring on each 

membrane unit according to the criteria in paragraphs (b)(4)(i) through (v) of this section. Indirect 

integrity monitoring is defined as monitoring some aspect of filtrate water quality that is indicative of the 

removal of particulate matter. A system that implements continuous direct integrity testing of membrane 

units in accordance with the criteria in paragraphs (b)(3)(i) through (v) of this section is not subject to the 

requirements for continuous indirect integrity monitoring. Systems must submit a monthly report to the 

State summarizing all continuous indirect integrity monitoring results triggering direct integrity testing and 

the corrective action that was taken in each case. 

(i) Unless the State approves an alternative parameter, continuous indirect integrity monitoring must 

include continuous filtrate turbidity monitoring. 

(ii) Continuous monitoring must be conducted at a frequency of no less than once every 15 minutes. 

(iii) Continuous monitoring must be separately conducted on each membrane unit. 

(iv) If indirect integrity monitoring includes turbidity and if the filtrate turbidity readings are above 0.15 

NTU for a period greater than 15 minutes ( i.e. , two consecutive 15-minute readings above 0.15 NTU), 

direct integrity testing must immediately be performed on the associated membrane unit as specified in 

paragraphs (b)(3)(i) through (v) of this section. 

(v) If indirect integrity monitoring includes a State-approved alternative parameter and if the alternative 

parameter exceeds a State-approved control limit for a period greater than 15 minutes, direct integrity 

testing must immediately be performed on the associated membrane units as specified in paragraphs (b)

(3)(i) through (v) of this section. 

(c) Second stage filtration. Systems receive 0.5-log Cryptosporidium treatment credit for a separate 

second stage of filtration that consists of sand, dual media, GAC, or other fine grain media following 

granular media filtration if the State approves. To be eligible for this credit, the first stage of filtration 

must be preceded by a coagulation step and both filtration stages must treat the entire plant flow taken 

from a surface water or GWUDI source. A cap, such as GAC, on a single stage of filtration is not eligible 

for this credit. The State must approve the treatment credit based on an assessment of the design 

characteristics of the filtration process. 

(d) Slow sand filtration (as secondary filter). Systems are eligible to receive 2.5-log Cryptosporidium 

treatment credit for a slow sand filtration process that follows a separate stage of filtration if both filtration 

stages treat entire plant flow taken from a surface water or GWUDI source and no disinfectant residual is 

present in the influent water to the slow sand filtration process. The State must approve the treatment 

credit based on an assessment of the design characteristics of the filtration process. This paragraph 

does not apply to treatment credit awarded to slow sand filtration used as a primary filtration process. 

[71 FR 769, Jan. 5, 2006; 71 FR 6136, Feb. 6, 2006] 

§ 141.720 Inactivation toolbox components. 

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(a) Calculation of CT values. (1) CT is the product of the disinfectant contact time (T, in minutes) and 

disinfectant concentration (C, in milligrams per liter). Systems with treatment credit for chlorine dioxide or 

ozone under paragraph (b) or (c) of this section must calculate CT at least once each day, with both C 

and T measured during peak hourly flow as specified in §§141.74(a) through (b). 

(2) Systems with several disinfection segments in sequence may calculate CT for each segment, where 

a disinfection segment is defined as a treatment unit process with a measurable disinfectant residual 

level and a liquid volume. Under this approach, systems must add the Cryptosporidium CT values in 

each segment to determine the total CT for the treatment plant. 

(b) CT values for chlorine dioxide and ozone. (1) Systems receive the Cryptosporidium treatment credit 

listed in this table by meeting the corresponding chlorine dioxide CT value for the applicable water 

temperature, as described in paragraph (a) of this section. 

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CT Values (mg·min/L) for Cryptosporidium Inactivation by Chlorine Dioxide1

1Systems may use this equation to determine log credit between the indicated values: Log credit = 

(0.001506 × (1.09116)Temp) × CT.

(2) Systems receive the Cryptosporidium treatment credit listed in this table by meeting the 

corresponding ozone CT values for the applicable water temperature, as described in paragraph (a) of 

this section. 

CT Values (mg·min/L) for Cryptosporidium Inactivation by Ozone1

1Systems may use this equation to determine log credit between the indicated values: Log credit = 

(0.0397 × (1.09757)Temp) × CT.

(c) Site-specific study. The State may approve alternative chlorine dioxide or ozone CT values to those 

listed in paragraph (b) of this section on a site-specific basis. The State must base this approval on a 

site-specific study a system conducts that follows a State-approved protocol. 

(d) Ultraviolet light. Systems receive Cryptosporidium, Giardia lamblia, and virus treatment credits for 

ultraviolet (UV) light reactors by achieving the corresponding UV dose values shown in paragraph (d)(1) 

of this section. Systems must validate and monitor UV reactors as described in paragraphs (d)(2) and 

(3) of this section to demonstrate that they are achieving a particular UV dose value for treatment credit. 

(1) UV dose table. The treatment credits listed in this table are for UV light at a wavelength of 254 nm as 

produced by a low pressure mercury vapor lamp. To receive treatment credit for other lamp types, 

systems must demonstrate an equivalent germicidal dose through reactor validation testing, as 

described in paragraph (d)(2) of this section. The UV dose values in this table are applicable only to 

post-filter applications of UV in filtered systems and to unfiltered systems. 

UV Dose Table for Cryptosporidium, Giardia lamblia, and Virus Inactivation Credit 

(2) Reactor validation testing. Systems must use UV reactors that have undergone validation testing to 

determine the operating conditions under which the reactor delivers the UV dose required in paragraph 

(d)(1) of this section ( i.e. , validated operating conditions). These operating conditions must include flow 

rate, UV intensity as measured by a UV sensor, and UV lamp status. 

(i) When determining validated operating conditions, systems must account for the following factors: UV 

absorbance of the water; lamp fouling and aging; measurement uncertainty of on-line sensors; UV dose 

distributions arising from the velocity profiles through the reactor; failure of UV lamps or other critical 

system components; and inlet and outlet piping or channel configurations of the UV reactor. 

(ii) Validation testing must include the following: Full scale testing of a reactor that conforms uniformly to 

the UV reactors used by the system and inactivation of a test microorganism whose dose response 

characteristics have been quantified with a low pressure mercury vapor lamp. 

Log credit

Water Temperature, °C

<=0.5 1 2 3 5 7 10 15 20 25 30

(i) 0.25 159 153 140 128 107 90 69 45 29 19 12

(ii) 0.5 319 305 279 256 214 180 138 89 58 38 24

(iii) 1.0 637 610 558 511 429 360 277 179 116 75 49

(iv) 1.5 956 915 838 767 643 539 415 268 174 113 73

(v) 2.0 1275 1220 1117 1023 858 719 553 357 232 150 98

(vi) 2.5 1594 1525 1396 1278 1072 899 691 447 289 188 122

(vii) 3.0 1912 1830 1675 1534 1286 1079 830 536 347 226 147

Log credit

Water Temperature, °C

<=0.5 1 2 3 5 7 10 15 20 25 30

(i) 0.25 6.0 5.8 5.2 4.8 4.0 3.3 2.5 1.6 1.0 0.6 0.39

(ii) 0.5 12 12 10 9.5 7.9 6.5 4.9 3.1 2.0 1.2 0.78

(iii) 1.0 24 23 21 19 16 13 9.9 6.2 3.9 2.5 1.6

(iv) 1.5 36 35 31 29 24 20 15 9.3 5.9 3.7 2.4

(v) 2.0 48 46 42 38 32 26 20 12 7.8 4.9 3.1

(vi) 2.5 60 58 52 48 40 33 25 16 9.8 6.2 3.9

(vii) 3.0 72 69 63 57 47 39 30 19 12 7.4 4.7

Log credit

Cryptosporidium 

UV dose (mJ/cm2)

Giardia lamblia 

UV dose (mJ/cm2)

Virus 

UV dose (mJ/cm2)

(i) 0.5 1.6 1.5 39

(ii) 1.0 2.5 2.1 58

(iii) 1.5 3.9 3.0 79

(iv) 2.0 5.8 5.2 100

(v) 2.5 8.5 7.7 121

(vi) 3.0 12 11 143

(vii) 3.5 15 15 163

(viii) 4.0 22 22 186

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(iii) The State may approve an alternative approach to validation testing. 

(3) Reactor monitoring. (i) Systems must monitor their UV reactors to determine if the reactors are 

operating within validated conditions, as determined under paragraph (d)(2) of this section. This 

monitoring must include UV intensity as measured by a UV sensor, flow rate, lamp status, and other 

parameters the State designates based on UV reactor operation. Systems must verify the calibration of 

UV sensors and must recalibrate sensors in accordance with a protocol the State approves. 

(ii) To receive treatment credit for UV light, systems must treat at least 95 percent of the water delivered 

to the public during each month by UV reactors operating within validated conditions for the required UV 

dose, as described in paragraphs (d)(1) and (2) of this section. Systems must demonstrate compliance 

with this condition by the monitoring required under paragraph (d)(3)(i) of this section. 

Reporting and Recordkeeping Requirements 

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§ 141.721 Reporting requirements. 

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(a) Systems must report sampling schedules under §141.702 and source water monitoring results under 

§141.706 unless they notify the State that they will not conduct source water monitoring due to meeting 

the criteria of §141.701(d). 

(b) Systems must report the use of uncovered finished water storage facilities to the State as described 

in §141.714. 

(c) Filtered systems must report their Cryptosporidium bin classification as described in §141.710. 

(d) Unfiltered systems must report their mean source water Cryptosporidium level as described in 

§141.712. 

(e) Systems must report disinfection profiles and benchmarks to the State as described in §§141.708 

through 141.709 prior to making a significant change in disinfection practice. 

(f) Systems must report to the State in accordance with the following table for any microbial toolbox 

options used to comply with treatment requirements under §141.711 or §141.712. Alternatively, the 

State may approve a system to certify operation within required parameters for treatment credit rather 

than reporting monthly operational data for toolbox options. 

Microbial Toolbox Reporting Requirements 

Toolbox option

Systems must submit the 

following information

On the following 

schedule

(1) Watershed 

control program 

(WCP)

(i) Notice of intention to 

develop a new or continue an 

existing watershed control 

program

No later than two years 

before the applicable 

treatment compliance date 

in §141.713

 (ii) Watershed control plan No later than one year 

before the applicable 

treatment compliance date 

in §141.713.

 (iii) Annual watershed control 

program status report

Every 12 months, 

beginning one year after 

the applicable treatment 

compliance date in 

§141.713.

 (iv) Watershed sanitary 

survey report

For community water 

systems, every three years 

beginning three years after 

the applicable treatment 

compliance date in 

§141.713. For 

noncommunity water 

systems, every five years 

beginning five years after 

the applicable treatment 

compliance date in 

§141.713.

(2) Alternative 

source/intake 

management

Verification that system has 

relocated the intake or 

adopted the intake withdrawal 

procedure reflected in 

monitoring results

No later than the 

applicable treatment 

compliance date in 

§141.713.

(3) 

Presedimentation

Monthly verification of the 

following: (i) Continuous 

basin operation (ii) Treatment 

of 100% of the flow (iii) 

Continuous addition of a 

Monthly reporting within 10 

days following the month in 

which the monitoring was 

conducted, beginning on 

the applicable treatment 

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coagulant (iv) At least 0.5-log 

mean reduction of influent 

turbidity or compliance with 

alternative State-approved 

performance criteria

compliance date in 

§141.713.

(4) Two-stage lime 

softening

Monthly verification of the 

following: (i) Chemical 

addition and hardness 

precipitation occurred in two 

separate and sequential 

softening stages prior to 

filtration (ii) Both stages 

treated 100% of the plant flow

Monthly reporting within 10 

days following the month in 

which the monitoring was 

conducted, beginning on 

the applicable treatment 

compliance date in 

§141.713.

(5) Bank filtration (i) Initial demonstration of the 

following: (A) Unconsolidated, 

predominantly sandy aquifer 

(B) Setback distance of at 

least 25 ft. (0.5-log credit) or 

50 ft. (1.0-log credit)

No later than the 

applicable treatment 

compliance date in 

§141.713.

 (ii) If monthly average of daily 

max turbidity is greater than 1 

NTU then system must report 

result and submit an 

assessment of the cause.

Report within 30 days 

following the month in 

which the monitoring was 

conducted, beginning on 

the applicable treatment 

compliance date in 

§141.713.

(6) Combined filter 

performance

Monthly verification of 

combined filter effluent (CFE) 

turbidity levels less than or 

equal to 0.15 NTU in at least 

95 percent of the 4 hour CFE 

measurements taken each 

month

Monthly reporting within 10 

days following the month in 

which the monitoring was 

conducted, beginning on 

the applicable treatment 

compliance date in 

§141.713.

(7) Individual filter 

performance

Monthly verification of the 

following: (i) Individual filter 

effluent (IFE ) turbidity levels 

less than or equal to 0.15 

NTU in at least 95 percent of 

samples each month in each 

filter (ii) No individual filter 

greater than 0.3 NTU in two 

consecutive readings 15 

minutes apart

Monthly reporting within 10 

days following the month in 

which the monitoring was 

conducted, beginning on 

the applicable treatment 

compliance date in 

§141.713.]

(8) Demonstration 

of performance

(i) Results from testing 

following a State approved 

protocol 

(ii) As required by the State, 

monthly verification of 

operation within conditions of 

State approval for 

demonstration of 

performance credit

No later than the 

applicable treatment 

compliance date in 

§141.713. 

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(9) Bag filters and 

cartridge filters

(i) Demonstration that the 

following criteria are met: (A) 

Process meets the definition 

of bag or cartridge filtration; 

(B) Removal efficiency 

established through 

challenge testing that meets 

criteria in this subpart

No later than the 

applicable treatment 

compliance date in 

§141.713.

 (ii) Monthly verification that 

100% of plant flow was 

filtered

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(10) Membrane 

filtration

(i) Results of verification 

testing demonstrating the 

following: (A) Removal 

efficiency established through 

challenge testing that meets 

criteria in this subpart; (B) 

No later than the 

applicable treatment 

compliance date in 

§141.713.

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§ 141.722 Recordkeeping requirements. 

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(a) Systems must keep results from the initial round of source water monitoring under §141.701(a) and 

the second round of source water monitoring under §141.701(b) until 3 years after bin classification 

under §141.710 for filtered systems or determination of the mean Cryptosporidium level under §141.710 

for unfiltered systems for the particular round of monitoring. 

(b) Systems must keep any notification to the State that they will not conduct source water monitoring 

due to meeting the criteria of §141.701(d) for 3 years. 

(c) Systems must keep the results of treatment monitoring associated with microbial toolbox options 

under §§141.716 through 141.720 and with uncovered finished water reservoirs under §141.714, as 

applicable, for 3 years. 

Requirements for Sanitary Surveys Performed by EPA 

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Integrity test method and 

parameters, including 

resolution, sensitivity, test 

frequency, control limits, and 

associated baseline

 (ii) Monthly report 

summarizing the following: 

(A) All direct integrity tests 

above the control limit; (B) If 

applicable, any turbidity or 

alternative state-approved 

indirect integrity monitoring 

results triggering direct 

integrity testing and the 

corrective action that was 

taken

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(11) Second stage 

filtration

Monthly verification that 

100% of flow was filtered 

through both stages and that 

first stage was preceded by 

coagulation step

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(12) Slow sand 

filtration (as 

secondary filter)

Monthly verification that both 

a slow sand filter and a 

preceding separate stage of 

filtration treated 100% of flow 

from subpart H sources.

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(13) Chlorine 

dioxide

Summary of CT values for 

each day as described in 

§141.720.

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(14) Ozone Summary of CT values for 

each day as described in 

§141.720.

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

(15) UV (i) Validation test results 

demonstrating operating 

conditions that achieve 

required UV dose 

(ii) Monthly report 

summarizing the percentage 

of water entering the 

distribution system that was 

not treated by UV reactors 

operating within validated 

conditions for the required 

dose as specified in 141.720

(d).

No later than the 

applicable treatment 

compliance date in 

§141.713. 

Within 10 days following 

the month in which 

monitoring was conducted, 

beginning on the 

applicable treatment 

compliance date in 

§141.713.

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§ 141.723 Requirements to respond to significant deficiencies identified in sanitary 

surveys performed by EPA. 

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(a) A sanitary survey is an onsite review of the water source (identifying sources of contamination by 

using results of source water assessments where available), facilities, equipment, operation, 

maintenance, and monitoring compliance of a PWS to evaluate the adequacy of the PWS, its sources 

and operations, and the distribution of safe drinking water. 

(b) For the purposes of this section, a significant deficiency includes a defect in design, operation, or 

maintenance, or a failure or malfunction of the sources, treatment, storage, or distribution system that 

EPA determines to be causing, or has the potential for causing the introduction of contamination into the 

water delivered to consumers. 

(c) For sanitary surveys performed by EPA, systems must respond in writing to significant deficiencies 

identified in sanitary survey reports no later than 45 days after receipt of the report, indicating how and 

on what schedule the system will address significant deficiencies noted in the survey. 

(d) Systems must correct significant deficiencies identified in sanitary survey reports according to the 

schedule approved by EPA, or if there is no approved schedule, according to the schedule reported 

under paragraph (c) of this section if such deficiencies are within the control of the system. 

Subpart X—Aircraft Drinking Water Rule 

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Source: 74 FR 53618, Oct. 19, 2009, unless otherwise noted. 

§ 141.800 Applicability and compliance date. 

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(a) Applicability. The requirements of this subpart constitute the National Primary Drinking Water 

Regulations for aircraft that are public water systems and that board only finished water for human 

consumption. Aircraft public water systems are considered transient non-community water systems 

(TNCWS). To the extent there is a conflict between the requirements in this subpart and the regulatory 

requirements established elsewhere in this part, this subpart governs. 

(b) Compliance date. Aircraft public water systems must comply, unless otherwise noted, with the 

requirements of this subpart beginning October 19, 2011. Until this compliance date, air carriers remain 

subject to existing national primary drinking water regulations. 

§ 141.801 Definitions. 

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As used in this subpart, the term: 

Administrator means the Administrator of the United States Environmental Protection Agency or his/her 

authorized representative. 

Air carrier means a person who undertakes directly by lease, or other arrangement, to engage in air 

transportation. The air carrier is responsible for ensuring all of the aircraft it owns or operates that are 

public water systems comply with all provisions of this subpart. 

Aircraft means a device that is used or intended to be used for flight in the air. 

Aircraft water system means an aircraft that qualifies as a public water system under the Safe Drinking 

Water Act and the national primary drinking water regulations. The components of an aircraft water 

system include the water service panel, the filler neck of the aircraft finished water storage tank, and all 

finished water storage tanks, piping, treatment equipment, and plumbing fixtures within the aircraft that 

supply water for human consumption to passengers or crew. 

Aircraft water system operations and maintenance plan means the schedules and procedures for 

operating, monitoring, and maintaining an aircraft water system that is included in an aircraft operation 

and maintenance program accepted by the Federal Aviation Administration. (14 CFR part 43, 14 CFR 

part 91, 14 CFR part 121) 

Finished water means water that is introduced into the distribution system of a public water system and 

is intended for distribution and consumption without further treatment, except as treatment necessary to 

maintain water quality in the distribution system (e.g., supplemental disinfection, addition of corrosion 

control chemicals). (40 CFR 141.2) 

Human consumption means drinking, bathing, showering, hand washing, teeth brushing, food 

preparation, dishwashing, and maintaining oral hygiene. 

Self inspection means an onsite review of the aircraft water system, including the water service panel, 

the filler neck of the aircraft finished water storage tank; all finished water storage tanks, piping, 

treatment equipment, and plumbing fixtures; and a review of the aircraft operations, maintenance, 

monitoring, and recordkeeping for the purpose of evaluating the adequacy of such water system 

components and practices for providing safe drinking water to passengers and crew. 

Watering point means the water supply, methods, and facilities used for the delivery of finished water to 

the aircraft. These facilities may include water trucks, carts, cabinets, and hoses. 

§ 141.802 Coliform sampling plan. 

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(a) Each air carrier under this subpart must develop a coliform sampling plan covering each aircraft 

water system owned or operated by the air carrier that identifies the following: 

(1) Coliform sample collection procedures that are consistent with the requirements of §141.803(a) and 

(b). 

(2) Sample tap location(s) representative of the aircraft water system as specified in §141.803(b)(2) and 

(b)(4). 

(3) Frequency and number of routine coliform samples to be collected as specified in §141.803(b)(3). 

(4) Frequency of routine disinfection and flushing as specified in the operations and maintenance plan 

under §141.804. 

(5) Procedures for communicating sample results promptly so that any required actions, including repeat 

and follow-up sampling, corrective action, and notification of passengers and crew, will be conducted in 

a timely manner. 

(b) Each air carrier must develop a coliform sampling plan for each aircraft with a water system meeting 

the definition of a public water system by April 19, 2011. 

(c) The coliform sampling plan must be included in the Aircraft Water System Operations and 

Maintenance Plan required in §141.804. Any subsequent changes to the coliform sampling plan must 

also be included in the Aircraft Water System Operations and Maintenance Plan required in §141.804. 

§ 141.803 Coliform sampling. 

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(a) Analytical methodology. Air carriers must follow the sampling and analysis requirements under this 

section. 

(1) The standard sample volume required for total coliform analysis, regardless of analytical method 

used, is 100 mL. 

(2) Air carriers need determine only the presence or absence of total coliforms and/or E. coli ; a 

determination of density of these organisms is not required. 

(3) Air carriers must conduct analyses for total coliform and E. coli in accordance with the analytical 

methods approved in §141.21(f)(3) and 141.21(f)(6). 

(4) The time from sample collection to initiation of analysis may not exceed 30 hours. Systems are 

encouraged but not required to hold samples below 10 °C during transit. 

(5) The invalidation of a total coliform sample result can be made only by the Administrator in 

accordance with §141.21(c)(1)(i), (ii), or (iii) or by the certified laboratory in accordance with §141.21(c)

(2). 

(6) Certified laboratories. For the purpose of determining compliance with this subpart, samples may be 

considered only if they have been analyzed by a laboratory certified by a State or EPA. For the purposes 

of this paragraph, “State” refers to a State or Tribe that has received primacy for public water systems 

(other than aircraft water systems) under section 1413 of SDWA. 

(b) Routine monitoring. For each aircraft water system, the sampling frequency must be determined by 

the disinfection and flushing frequency recommended by the aircraft water system manufacturer, when 

available, and as identified in the operations and maintenance plan in §141.804. 

(1) Except as provided in paragraph (b)(2) of this section, the air carrier must collect two 100 mL total 

coliform routine samples at the frequency specified in the sampling plan in §141.802 and in accordance 

with paragraph (b)(3) of this section; 

(2) The air carrier may collect one 100 mL total coliform routine sample at the frequency specified in the 

sampling plan in §141.802 for aircraft with a removable or portable tank that is drained every day of 

passenger service, and the aircraft has only one tap. Aircraft meeting the requirements of this paragraph 

do not have to comply with paragraph (b)(4) of this section. 

(3) Air carriers must perform routine monitoring for total coliform at a frequency corresponding to the 

frequency of routine disinfection and flushing as specified in the Table b–1 (Routine Disinfection and 

Flushing and Routine Sample Frequencies). Air carriers must follow the disinfection and flushing 

frequency recommended by the aircraft water system manufacturer, when available. Where the aircraft 

water system manufacturer does not specify a recommended routine disinfection and flushing 

frequency, the air carrier must choose a frequency from Table b–1 (Routine Disinfection and Flushing 

and Routine Sample Frequencies): 

Table B–1—Routine Disinfection and Flushing and Routine Sample Frequencies 

Minimum routine disinfection & 

flushing per 

aircraft

Minimum frequency of routine 

samples per 

aircraft

At least 4 times per year = At least once 

within every three-month period 

(quarterly)

At least 1 time per year = At least 

once within every twelve-month 

period (annually).

At least 3 times per year = At least once 

within every four-month period

At least 2 times per year = At least 

once within every six-month period 

(semi-annually).

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(4) One sample must be taken from a lavatory and one from a galley; each sample must be analyzed for 

total coliform. If only one water tap is located in the aircraft water system due to aircraft model type and 

construction, then a single tap may be used to collect two separate 100 mL samples. 

(5) If any routine, repeat, or follow-up coliform sample is total coliform-positive, the air carrier must 

analyze that total coliform-positive culture medium to determine if E. coli is present. 

(6) Routine total coliform samples must not be collected within 72 hours after completing routine 

disinfection and flushing procedures. 

(c) Routine coliform sample results —(1) Negative routine coliform sample results. If all routine sample 

results are total coliform-negative, then the air carrier must maintain the routine monitoring frequency for 

total coliform as specified in the sampling plan in §141.802. 

(2) Positive routine E. coli sample results. If any routine sample is E. coli -positive, the air carrier must 

perform all of the following: 

(i) Restrict public access. Restrict public access to the aircraft water system in accordance with 

paragraph (d) of this section as expeditiously as possible, but in no case later than 24 hours after the 

laboratory notifies the air carrier of the E. coli -positive result or discovery of the applicable failure as 

specified in paragraphs (g) and (h) of this section. All public access restrictions, including applicable 

public notification requirements, must remain in-place until the aircraft water system has been 

disinfected and flushed and a complete set of follow-up samples is total coliform-negative; and 

(ii) Disinfect and flush. Conduct disinfection and flushing in accordance with §141.804(b)(2). If the 

aircraft water system cannot be physically disconnected or shut-off, or the flow of water otherwise 

prevented through the tap(s), then the air carrier must disinfect and flush the system no later than 72 

hours after the laboratory notifies the air carrier of the E. coli -positive result or discovery of the 

applicable failure as specified in paragraphs (g) and (h) of this section; and 

(iii) Follow-up sampling. Collect follow-up samples in accordance with paragraph (e) of this section. A 

complete set of follow-up sample results must be total coliform-negative before the air carrier provides 

water for human consumption from the aircraft water system and returns to the routine monitoring 

frequency as specified in the sampling plan required by §141.802. 

(3) Positive routine total coliform sample results. If any routine sample is total coliform-positive and E. 

coli -negative, then the air carrier must perform at least one of the following three corrective actions and 

continue through with that action until a complete set of follow-up or repeat samples is total coliformnegative: 

(i) Disinfect and flush. In accordance with §141.804(b)(2), conduct disinfection and flushing of the 

system no later than 72 hours after the laboratory notifies the air carrier of the total coliform-positive and 

E. coli -negative result. After disinfection and flushing is completed, the air carrier must collect follow-up 

samples in accordance with paragraph (e) of this section prior to providing water for human consumption 

from the aircraft water system. A complete set of follow-up sample results must be total coliformnegative before the air carrier returns to the routine monitoring frequency as specified in the sampling 

plan required by §141.802; or 

(ii) Restrict public access. In accordance with paragraph (d) of this section, restrict public access to the 

aircraft water system as expeditiously as possible, but in no case later than 72 hours after the laboratory 

notifies the air carrier of the total coliform-positive and E. coli -negative result or discovery of the 

applicable failure as specified in paragraphs (f), (g), and, (i) of this section. All public access restrictions, 

including applicable public notification requirements, must remain in-place until the aircraft water system 

has been disinfected and flushed, and a complete set of follow-up samples has been collected. The air 

carrier must conduct disinfection and flushing in accordance with §141.804(b)(2). After disinfection and 

flushing is completed, the air carrier must collect follow-up samples in accordance with paragraph (e) of 

this section prior to providing water for human consumption from the aircraft water system. A complete 

set of follow-up sample results must be total coliform-negative before the air carrier returns to the routine 

monitoring frequency as specified in the sampling plan required by §141.802; or 

(iii) Repeat sampling. Collect three 100 mL repeat samples no later than 24 hours after the laboratory 

notifies the air carrier of the routine total coliform-positive and E. coli -negative result. Repeat samples 

must be collected and analyzed from three taps within the aircraft as follows: The tap which resulted in 

the total coliform-positive sample, one other lavatory tap, and one other galley tap. If fewer than three 

taps exist, then a total of three 100 mL samples must be collected and analyzed from the available taps 

within the aircraft water system. 

(A) If all repeat samples are total coliform-negative, then the air carrier must maintain the routine 

monitoring frequency for total coliform as specified in the sampling plan in §141.802. 

(B) If any repeat sample is E. coli -positive, the air carrier must perform all the corrective actions as 

specified in paragraphs (c)(2)(i), (c)(2)(ii), and (c)(2)(iii) of this section. 

(C) If any repeat sample is total coliform-positive and E. coli -negative, then the air carrier must perform 

the corrective actions specified in paragraphs (c)(3)(i) or (c)(3)(ii) of this section, and continue through 

with that action until a complete set of follow-up samples is total coliform-negative. 

(d) Restriction of public access. Restriction of public access to the aircraft water system includes, but 

need not be limited to, the following: 

(1) Physically disconnecting or shutting off the aircraft water system, where feasible, or otherwise 

preventing the flow of water through the tap(s); 

(2) Providing public notification to passengers and crew in accordance with §141.805. 

At least 2 times per year = At least once 

within every six-month period (semiannually)

At least 4 times per year = At least 

once within every three-month 

period (quarterly).

At least 1 time per year or less = At least 

once within every twelve-month period 

(annually) or less

At least 12 times per year = At least 

once every month (monthly).

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(3) Providing alternatives to water from the aircraft water system, such as bottled water for drinking and 

coffee or tea preparation; antiseptic hand gels or wipes in accordance with 21 CFR part 333—“Topical 

Anti-microbial Drug Products for Over-the-Counter Human Use” in the galleys and lavatories; and other 

feasible measures that reduce or eliminate the need to use the aircraft water system during the limited 

period before public use of the aircraft water system is unrestricted. 

(e) Post disinfection and flushing follow-up sampling. Following corrective action disinfection and 

flushing, air carriers must comply with post disinfection and flushing follow-up sampling procedures that, 

at a minimum, consist of the following: 

(1) For each aircraft water system, the air carrier must collect a complete set of total coliform follow-up 

samples consisting of two 100 mL total coliform samples at the same routine sample locations as 

identified in paragraphs (b)(2) and (b)(4) of this section. 

(2) Follow-up samples must be collected prior to providing water to the public for human consumption 

from the aircraft water system. 

(3) If a complete set of follow-up samples is total coliform-negative, the air carrier must return to the 

routine monitoring frequency for total coliform as specified in the sampling plan required by §141.802. 

(4) If any follow-up sample is E. coli -positive, the air carrier must perform all the corrective actions as 

specified in paragraphs (c)(2)(i), (c)(2)(ii), and (c)(2)(iii) of this section. 

(5) If any follow-up sample is total coliform-positive and E. coli -negative the air carrier must restrict 

public access to the aircraft water system in accordance with paragraph (d) of this section as 

expeditiously as possible, but in no case later than 72 hours after the laboratory notifies the air carrier of 

the total coliform-positive and E. coli -negative result. All public access restrictions, including applicable 

public notification requirements, must remain in-place until the aircraft water system has been 

disinfected and flushed in accordance with §141.804(b)(2) and a complete set of follow-up samples is 

total coliform-negative. The air carrier must collect follow-up samples in accordance with paragraph (e) 

of this section. A complete set of follow-up sample results must be total coliform-negative before the air 

carrier provides water for human consumption from the aircraft water system and returns to the routine 

monitoring frequency for coliform as specified in §141.802. 

(f) Failure to perform required routine disinfection and flushing or failure to collect required routine 

samples. If the air carrier fails to perform routine disinfection and flushing or fails to collect and analyze 

the required number of routine coliform samples, the air carrier must perform all the corrective actions as 

specified in paragraph (c)(3)(ii) of this section. 

(g) Failure to collect repeat or follow-up samples. If the air carrier fails to collect and analyze the required 

follow-up samples as a result of an E. coli -positive result, then the air carrier must perform all the 

corrective actions as specified in paragraphs (c)(2)(i), (c)(2)(ii), and (c)(2)(iii) of this section. If the air 

carrier fails to collect and analyze the required repeat samples or follow-up samples as a result of a total 

coliform-positive and E. coli -negative result, then the air carrier must perform all the corrective actions 

as specified in paragraph (c)(3)(ii) of this section. 

(h) Failure to board water from a safe watering point (E. coli-positive). For the aircraft water system, the 

air carrier must perform all the corrective actions specified in paragraphs (c)(2)(i), (c)(2)(ii), and (c)(2)(iii) 

of this section when it becomes aware of an E. coli -positive event resulting from: 

(1) Boarding water from a watering point not in accordance with FDA regulations (21 CFR part 1240 

subpart E), or 

(2) Boarding water that does not meet NPDWRs applicable to transient non-community water systems 

(§§141.62 and 141.63, as applied to TNCWS), 

(3) Boarding water that is otherwise determined to be unsafe due to non-compliance with the procedures 

specified in §141.804(b)(6). 

(i) Failure to board water from a safe watering point (non-E. coli-positive). For the aircraft water system, 

the air carrier must perform all the corrective actions specified in paragraphs (c)(3)(ii) of this section 

when it becomes aware of a non- E. coli -positive event resulting from: 

(1) Boarding water from a watering point not in accordance with FDA regulations (21 CFR part 1240, 

subpart E), 

(2) Boarding water that does not meet NPDWRs applicable to transient non-community water systems 

(§§141.62 and 141.63, as applied to TNCWS), or 

(3) Boarding water that is otherwise determined to be unsafe due to non-compliance with the procedures 

specified in §141.804(b)(6). 

§ 141.804 Aircraft water system operations and maintenance plan. 

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(a) Each air carrier must develop and implement an aircraft water system operations and maintenance 

plan for each aircraft water system that it owns or operates. This plan must be included in a Federal 

Aviation Administration (FAA)-accepted air carrier operations and maintenance program (14 CFR part 

43, 14 CFR part 91, 14 CFR part 121). 

(b) Each aircraft water system operations and maintenance plan must include the following: 

(1) Watering point selection requirement. All watering points must be selected in accordance with Food 

and Drug Administration (FDA) regulations (21 CFR part 1240, subpart E). 

(2) Procedures for disinfection and flushing. The plan must include the following requirements for 

procedures for disinfection and flushing of aircraft water system. 

(i) The air carrier must conduct disinfection and flushing of the aircraft water system in accordance with, 

or is consistent with, the water system manufacturer's recommendations. The air carrier may conduct 

disinfection and flushing more frequently, but not less frequently, than the manufacturer recommends. 

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(ii) The operations and maintenance plan must identify the disinfection frequency, type of disinfecting 

agent, disinfectant concentration to be used, and the disinfectant contact time, and flushing volume or 

flushing time. 

(iii) In cases where a recommended routine disinfection and flushing frequency is not specified by the 

aircraft water system manufacturer, the air carrier must choose a disinfection and flushing, and 

corresponding monitoring frequency specified in §141.803(b)(3). 

(3) Follow-up sampling. The plan must include the procedures for follow-up sampling in accordance with 

§141.803(e). 

(4) Training requirements. Training for all personnel involved with the aircraft water system operation 

and maintenance provisions of this regulation must include, but is not limited to the following: 

(i) Boarding water procedures; 

(ii) Sample collection procedures; 

(iii) Disinfection and flushing procedures; 

(iv) Public health and safety reasons for the requirements of this subpart. 

(5) Procedures for conducting self-inspections of the aircraft water system. Procedures must include, but 

are not limited to, inspection of storage tank, distribution system, supplemental treatment, fixtures, 

valves, and backflow prevention devices. 

(6) Procedures for boarding water. The plan must include the following requirements and procedures for 

boarding water: 

(i) Within the United States, the air carrier must board water from watering points in accordance with 

Food and Drug Administration (FDA) regulations (21 CFR part 1240, subpart E). 

(ii) A description of how the water will be transferred from the watering point to the aircraft in a manner 

that ensures it will not become contaminated during the transfer. 

(iii) A description of how the carrier will ensure that water boarded outside the United States is safe for 

human consumption. 

(iv) A description of emergency procedures that meet the requirements in §141.803(h) and (i) that must 

be used in the event that the air carrier becomes aware that water was boarded to operate essential 

systems, such as toilets, but was boarded from a watering point not in accordance with FDA regulations, 

does not meet NPDWRs applicable to transient non-community water systems (§§141.62 and 141.63, 

as applied to TNCWSs), or is otherwise unsafe. 

(7) Coliform sampling plan. The air carrier must include the coliform sampling plan prepared in 

accordance with §141.802. 

(8) Aircraft water system disconnect/shut-off, or prevent flow of water through the tap(s) statement. An 

explanation of whether the aircraft water system can be physically disconnected/shut-off, or the flow of 

water otherwise prevented through the tap(s) to the crew and passengers. 

(c) For existing aircraft, the air carrier must develop the water system operations and maintenance plan 

required by this section by April 19, 2011; 

(d) For new aircraft, the air carrier must develop the operations and maintenance plan required in this 

section within the first calendar quarter of initial operation of the aircraft. 

(e) Any changes to the aircraft water system operations and maintenance plan must be included in the 

FAA-accepted air carrier operations and maintenance program. 

§ 141.805 Notification to passengers and crew. 

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(a) Air carriers must give public notice for each aircraft in all of the following situations: 

(1) Public access to the aircraft water system is restricted in response to a routine, repeat or follow-up 

total coliform-positive or E. coli -positive sample result in accordance with §141.803(d); 

(2) Failure to perform required routine disinfection and flushing or failure to collect required routine 

samples in accordance with §141.803(f); 

(3) Failure to collect the required follow-up samples in response to a sample result that is E. coli -positive 

in accordance with §141.803(g); 

(4) Failure to collect the required repeat samples or failure to collect the required follow-up samples in 

response to a sample result that is total coliform-positive and E. coli -negative in accordance with 

§141.803(g); 

(5) In accordance with §141.803(h), the air carrier becomes aware of an E. coli -positive event resulting 

from water that has been boarded from a watering point not in accordance with FDA regulations (21 

CFR part 1240, subpart E), or that does not meet NPDWRs applicable to transient non-community water 

systems, or that is otherwise determined to be unsafe due to non-compliance with the procedures 

specified in §141.804(b)(6); 

(6) In accordance with §141.803(i), the air carrier becomes aware of a non- E. coli -positive event 

resulting from water that has been boarded from a watering point not in accordance with FDA 

regulations (21 CFR part 1240, subpart E), or that does not meet NPDWRs applicable to transient noncommunity water systems, or that is otherwise determined to be unsafe due to non-compliance with the 

procedures specified in §141.804(b)(6). 

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(7) The Administrator, the carrier, or the crew otherwise determines that notification is necessary to 

protect public health. 

(b) Public notification: (1) Must be displayed in a conspicuous way when printed or posted; 

(2) Must not contain overly technical language or very small print; 

(3) Must not be formatted in a way that defeats the purpose of the notice; 

(4) Must not contain language that nullifies the purpose of the notice; 

(5) Must contain information in the appropriate language(s) regarding the importance of the notice, 

reflecting a good faith effort to reach the non-English speaking population served, including, where 

applicable, an easily recognized symbol for non-potable water. 

(c) Public notification for paragraph (a)(1) of this section must meet the requirements of paragraph (b) of 

this section in addition to the following: 

(1) Public notification must include a prominently displayed, clear statement in each lavatory indicating 

that the water is non-potable and should not be used for drinking, food or beverage preparation, hand 

washing, teeth brushing, or any other consumptive use; and 

(2) A prominent notice in the galley directed at the crew which includes: 

(i) A clear statement that the water is non-potable and should not be used for drinking, food or beverage 

preparation, hand washing, teeth brushing, or any other consumptive use; 

(ii) A description of the violation or situation triggering the notice, including the contaminant(s) of 

concern; 

(iii) When the violation or situation occurred; 

(iv) Any potential adverse health effects from the violation or situation, as appropriate, under paragraph 

(g) of this section; 

(v) The population at risk, including sensitive subpopulations particularly vulnerable if exposed to the 

contaminant in the drinking water; 

(vi) What the air carrier is doing to correct the violation or situation; and 

(vii) When the air carrier expects to return the system to unrestricted public access. 

(3) If passenger access to the water system is physically prevented through disconnecting or shutting off 

the water, or the flow of water prevented through the tap(s), or if water is supplied only to lavatory toilets, 

and not to any lavatory or galley taps, then only the notice specified in paragraph (c)(2) of this section is 

required. 

(4) Air carriers must initiate public notification when restriction of public access is initiated in accordance 

with §141.803(d) and must continue until the aircraft water system is returned to unrestricted public 

access. 

(d) Public notification for paragraphs (a)(2), (a)(4), and (a)(6) of this section must meet the requirements 

of paragraph (b) of this section in addition to the following: 

(1) Public notification must include a prominently displayed, clear statement in each lavatory indicating 

that the water is non-potable and should not be used for drinking, food or beverage preparation, hand 

washing, teeth brushing, or any other consumptive use; and 

(2) A prominent notice in the galley directed at the crew which includes: 

(i) A clear statement that the water is non-potable and should not be used for drinking, food or beverage 

preparation, hand washing, teeth brushing, or any other consumptive use; 

(ii) A clear statement that it is not known whether the water is contaminated because there was a failure 

to perform required routine disinfection and flushing; or a failure to perform required monitoring; or water 

was boarded from a watering point not in accordance with FDA regulations, or that does not meet 

NPDWRs applicable to transient noncommunity water systems, or that is otherwise determined to be 

unsafe due to noncompliance with the procedures specified in §141.804(b)(6); 

(iii) When and where the unsafe water was boarded or when the specific monitoring or disinfection and 

flushing requirement was not met; 

(iv) Any potential adverse health effects from exposure to waterborne pathogens that might be in the 

water, as appropriate, under paragraph (g) of this section; 

(v) The population at risk, including sensitive subpopulations particularly vulnerable if exposed to the 

contaminant in the drinking water; and 

(vi) A statement indicating when the system will be disinfected and flushed and returned to unrestricted 

public access. 

(3) If passenger access to the water system is physically prevented through disconnecting or shutting off 

the water, or the flow of water prevented through the tap(s), or if water is supplied only to lavatory toilets, 

and not to any lavatory or galley taps, then only the notice specified in paragraph (d)(2) of this section is 

required. 

(4) Air carriers must initiate public notification when restriction of public access is initiated in accordance 

with §141.803(d) and must continue until the aircraft water system is returned to unrestricted public 

access. 

(e) Public notification for paragraphs (a)(3) and (a)(5) of this section must meet the requirements of 

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paragraph (b) of this section in addition to the following: 

(1) Public notification must include a prominently displayed, clear statement in each lavatory indicating 

that the water is non-potable and should not be used for drinking, food or beverage preparation, hand 

washing, teeth brushing, or any other consumptive use; and 

(2) A prominent notice in the galley directed at the crew which includes: 

(i) A clear statement that the water is non-potable and should not be used for drinking, food or beverage 

preparation, hand washing, teeth brushing, or any other consumptive use; 

(ii) A clear statement that the water is contaminated and there was a failure to conduct required 

monitoring; or a clear statement that water is contaminated because water was boarded from a watering 

point not in accordance with FDA regulations, or that does not meet NPDWRs applicable to transient 

noncommunity water systems, or that is otherwise determined to be unsafe due to noncompliance with 

the procedures specified in §141.804(b)(6); 

(iii) A description of the contaminant(s) of concern; 

(iv) When and where the unsafe water was boarded or when the specific monitoring requirement was 

not met; 

(v) Any potential adverse health effects from the situation, as appropriate, under paragraph (g) of this 

section; 

(vi) The population at risk, including sensitive subpopulations particularly vulnerable if exposed to the 

contaminant in the drinking water; 

(vii) A statement indicating what the air carrier is doing to correct the situation; and 

(viii) When the air carrier expects to return the system to unrestricted public access. 

(3) If passenger access to the water system is physically prevented through disconnecting or shutting off 

the water, or the flow of water prevented through the tap(s), or if water is supplied only to lavatory toilets, 

and not to any lavatory or galley taps, then only the notice specified in paragraph (e)(2) of this section is 

required. 

(4) Air carriers must initiate public notification when restriction of public access is initiated in accordance 

with §141.803(d) and must continue public notification until a complete set of required follow-up samples 

are total coliform-negative. 

(f) Public notification for paragraph (a)(7) of this section must meet the requirements of paragraph (b) of 

this section in addition to the following: 

(1) Notification must be in a form and manner reasonably calculated to reach all passengers and crew 

while on board the aircraft by using one or more of the following forms of delivery: 

(i) Broadcast over public announcement system on aircraft; 

(ii) Posting of the notice in conspicuous locations throughout the area served by the water system. 

These locations would normally be the galleys and in the lavatories of each aircraft requiring posting; 

(iii) Hand delivery of the notice to passengers and crew; 

(iv) Another delivery method approved in writing by the Administrator. 

(2) Air carriers must initiate public notification within 24 hours of being informed by EPA to perform 

notification and must continue notification for the duration determined by EPA. 

(g) In each public notice to the crew, air carriers must use the following standard health effects language 

that corresponds to the situations in paragraphs (a)(1) through (a)(6) of this section. 

(1) Health effects language to be used when public notice is initiated due to the detection of total 

coliforms only (not E. coli ) in accordance with paragraph (a)(1) of this section: 

Coliform are bacteria that are naturally present in the environment and are used as an 

indicator that other, potentially harmful, bacteria may be present. Coliforms were found in 

[INSERT NUMBER OF SAMPLES DETECTED] samples collected and this is a warning of 

potential problems. If human pathogens are present, they can cause short-term health effects, 

such as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special 

health risk for infants, young children, some of the elderly, and people with severely 

compromised immune systems. 

(2) Health effects language to be used when public notice is initiated due to any E. coli -positive routine, 

repeat, or follow-up sample in accordance with paragraph (a)(1) of this section: 

E. coli are bacteria whose presence indicates that the water may be contaminated with 

human or animal wastes. Microbes in these wastes can cause short-term health effects, such 

as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health 

risk for infants, young children, some of the elderly, and people with severely compromised 

immune systems. 

(3) Health effects language to be used when public notice is initiated due to a failure to conduct routine 

monitoring or routine disinfection and flushing in accordance with paragraph (a)(2) of this section; or 

when there is a failure to conduct repeat or follow-up sampling in accordance with paragraph (a)(4) of 

this section; or in accordance with paragraph (a)(6) of this section, when the air carrier becomes aware 

of a non- E. coli -positive event that is the result of water that was boarded from a watering point not in 

accordance with FDA regulations (21 CFR part 1240, subpart E), or that does not meet NPDWRs 

applicable to transient non-community water systems, or that is otherwise determined to be unsafe due 

to non-compliance with the procedures specified in §141.804(b)(6): 

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Because [REQUIRED MONITORING AND ANALYSIS WAS NOT CONDUCTED], 

[REQUIRED DISINFECTION AND FLUSHING WAS NOT CONDUCTED] [WATER WAS 

BOARDED FROM A WATERING POINT NOT IN ACCORDANCE WITH FDA 

REGULATIONS (21 CR 1240 SUBPART E)], or [OTHER APPROPRIATE EXPLANATION], 

we cannot be sure of the quality of the drinking water at this time. However, drinking water 

contaminated with human pathogens can cause short-term health effects, such as diarrhea, 

cramps, nausea, headaches, or other symptoms. They may pose a special health risk for 

infants, young children, some of the elderly, and people with severely compromised immune 

systems. 

(4) Health effects language to be used when public notice is initiated due to a failure to conduct required 

follow-up monitoring in response to a sample result that is E. coli -positive in accordance with paragraph 

(a)(3) of this section; or in accordance with paragraph (a)(5) of this section, when the air carrier becomes 

aware of an E. coli -positive event that is the result of water that was boarded from a watering point not 

in accordance with FDA regulations (21 CFR part 1240, subpart E), or that does not meet NPDWRs 

applicable to transient non-community water systems, or that is otherwise determined to be unsafe due 

to non-compliance with the procedures specified in §141.804(b)(6): 

Because required follow-up monitoring and analysis was not conducted after the aircraft water 

system tested positive for E. coli, we cannot be sure of the quality of the drinking water at this 

time. E. coli are bacteria whose presence indicates that the water may be contaminated with 

human or animal wastes. Microbes in these wastes can cause short-term health effects, such 

as diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health 

risk for infants, young children, some of the elderly, and people with severely compromised 

immune systems. 

OR 

Water was boarded that is contaminated with E. coli because [WATER WAS BOARDED 

FROM A WATERING POINT NOT IN ACCORDANCE WITH FDA REGULATIONS (21 CR 

1240 SUBPART E)], or [OTHER APPROPRIATE EXPLANATION]. E. coli are bacteria whose 

presence indicates that the water may be contaminated with human or animal wastes. 

Microbes in these wastes can cause short-term health effects, such as diarrhea, cramps, 

nausea, headaches, or other symptoms. They may pose a special health risk for infants, 

young children, some of the elderly, and people with severely compromised immune systems. 

§ 141.806 Reporting requirements. 

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(a) The air carrier must comply with the following requirements regarding reporting of the development of 

the coliform sampling plan, the operations and maintenance plan, and the disinfection and flushing and 

coliform sampling frequencies. 

(1) The air carrier must report to the Administrator that it has developed the coliform sampling plan 

required by §141.802, which covers each existing aircraft water system, as well as report the frequency 

for routine coliform sampling identified in the coliform sampling plan by April 19, 2011. The air carrier 

must report to the Administrator that it has developed its operations and maintenance plan required by 

§141.804 and report the frequency for routine disinfection and flushing by April 19, 2011; 

(2) For each new aircraft meeting the definition of an aircraft water system, which becomes operational 

after publication of this subpart, the air carrier must report to the Administrator that it has developed the 

coliform sampling plan required by §141.802, as well as report the frequency for routine coliform 

sampling identified in the coliform sampling plan, within the first calendar quarter of initial operation of 

the aircraft. The air carrier must report to the Administrator that it has developed the aircraft water 

system operations and maintenance plan required by §141.804, and report the frequency for routine 

disinfection and flushing within the first calendar quarter of initial operation of the aircraft. 

(b) The air carrier must report the following information to the Administrator: 

(1) A complete inventory of aircraft that are public water systems by April 19, 2011. Inventory information 

includes, at a minimum, the following: 

(i) The unique aircraft identifier number; 

(ii) The status (active or inactive) of any aircraft as an aircraft water system as defined in §141.801; 

(iii) The type and location of any supplemental treatment equipment installed on the water system; and 

(iv) Whether the aircraft water system can be physically disconnected or shut-off, or the flow of water 

prevented through the tap(s). 

(2) Changes in aircraft inventory no later than 10 days following the calendar month in which the change 

occurred. Changes in inventory information include, at a minimum, the following: 

(i) Change in the unique identifier number for any new aircraft, or any aircraft removed from the carrier's 

fleet; 

(ii) Change in status (active or inactive) of any aircraft as an aircraft water system as defined in 

§141.801; and 

(iii) Change to the type and location of any supplemental treatment equipment added to or removed from 

the water system. 

(iv) Change to whether the aircraft water system can be physically disconnected or shut-off, or the flow 

of water prevented through the tap(s). 

(3) All sampling results no later than 10 calendar days following the monitoring period in which the 

sampling occurred. The monitoring period is based on the monitoring frequency identified in the coliform 

sampling plan required under §141.802. Routine disinfection and flushing events must be reported no 

later than 10 calendar days following the disinfection and flushing period in which the disinfection and 

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flushing occurred. The disinfection and flushing period is based on the frequency identified in the 

operations and maintenance plan required under §141.804. 

(4) All events requiring notification to passengers or crew, or non-routine disinfection and flushing, or 

non-routine sampling, within 10 days of the event (e.g., notification of positive sample result by 

laboratory), including information on whether required notification was provided to passengers or crew or 

both. 

(5) Failure to comply with the monitoring or disinfection and flushing requirements of this subpart within 

10 calendar days of discovery of the failure. 

(6) Changes in disinfection and flushing and coliform sampling frequencies no later than 10 days 

following the calendar month in which the change occurred. Changes to an aircraft's routine coliform 

sampling frequency and routine disinfection and flushing frequency must be included in the aircraft water 

system operation and maintenance plan that is included in the air carrier operations and maintenance 

program accepted by FAA in accordance with §141.804. 

(c) The air carrier must provide evidence of a self-inspection to the Administrator within 90 days of 

completion of the self-inspection required under §141.808(b), including reporting whether all deficiencies 

were addressed in accordance with §141.808(c). The air carrier must also report to the Administrator 

within 90 days that any deficiency identified during a compliance audit conducted in accordance with 

§141.808(a) has been addressed. If any deficiency has not been addressed within 90 days of 

identification of the deficiency, the report must also include a description of the deficiency, an 

explanation as to why it has not yet been addressed, and a schedule for addressing it as expeditiously 

as possible. 

(d) All information required to be reported to the Administrator under this subpart must be in an 

electronic format established or approved by the Administrator. If an air carrier is unable to report 

electronically, the air carrier may use an alternative approach that the Administrator approves. 

§ 141.807 Recordkeeping requirements. 

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(a) The air carrier must keep records of bacteriological analyses for at least 5 years and must include the 

following information: 

(1) The date, time, and place of sampling, and the name of the person who collected the sample; 

(2) Identification of the sample as a routine, repeat, follow-up, or other special purpose sample; 

(3) Date of the analysis; 

(4) Laboratory and person responsible for performing the analysis; 

(5) The analytical technique/method used; and 

(6) The results of the analysis. 

(b) The air carrier must keep records of any disinfection and flushing for at least 5 years and must 

include the following information: 

(1) The date and time of the disinfection and flushing; and 

(2) The type of disinfection and flushing ( i.e. , routine or corrective action). 

(c) The air carrier must keep records of a self-inspection for at least 10 years and must include the 

following information: 

(1) The completion date of the self-inspection; and 

(2) Copies of any written reports, summaries, or communications related to the self-inspection. 

(d) The air carrier must maintain sampling plans and make such plans available for review by the 

Administrator upon request, including during compliance audits. 

(e) The air carrier must maintain aircraft water system operations and maintenance plans in accordance 

with FAA requirements, and make such plans available for review by the Administrator upon request, 

including during compliance audits. 

(f) The air carrier must keep copies of public notices to passengers and crew issued as required by this 

subpart for at least 3 years after issuance. 

§ 141.808 Audits and inspections. 

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(a) The Administrator may conduct routine compliance audits as deemed necessary in providing 

regulatory oversight to ensure proper implementation of the requirements in this subpart. Compliance 

audits may include, but are not limited to: 

(1) Bacteriological sampling of aircraft water system; 

(2) Reviews and audits of records as they pertain to water system operations and maintenance such as 

log entries, disinfection and flushing procedures, and sampling results; and 

(3) Observation of procedures involving the handling of finished water, watering point selection, boarding 

of water, operation, disinfection and flushing, and general maintenance and self-inspections of aircraft 

water system. 

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(b) Air carriers or their representatives must perform a self-inspection of all water system components for 

each aircraft water system no less frequently than once every 5 years. 

(c) The air carrier must address any deficiency identified during compliance audits or routine selfinspections within 90 days of identification of the deficiency, or where such deficiency is identified during 

extended or heavy maintenance, before the aircraft is put back into service. This includes any deficiency 

in the water system's design, construction, operation, maintenance, or administration, as well as any 

failure or malfunction of any system component that has the potential to cause an unacceptable risk to 

health or that could affect the reliable delivery of safe drinking water. 

§ 141.809 Supplemental treatment. 

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(a) Any supplemental drinking water treatment units installed onboard existing or new aircraft must be 

acceptable to FAA and FDA; and must be installed, operated, and maintained in accordance with the 

manufacturer's plans and specifications and FAA requirements. 

(b) Water supplemental treatment and production equipment must produce water that meets the 

standards prescribed in this part. 

§ 141.810 Violations. 

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An air carrier is in violation of this subpart when, for any aircraft water system it owns or operates, any of 

the following occur: 

(a) It fails to perform any of the requirements in accordance with §141.803 or §141.804. 

(b) It has an E. coli -positive sample in any monitoring period (routine and repeat samples are used in 

this determination). 

(c) It fails to provide notification to passengers and crew in accordance with §141.805. 

(d) It fails to comply with the reporting and recordkeeping requirements of this subpart. 

(e) It fails to conduct a self-inspection or address a deficiency in accordance with §141.808. 

(f) It fails to develop a coliform sampling plan in accordance with §141.802, or fails to have and follow an 

operations and maintenance plan, which is included in a FAA accepted program in accordance with 

§141.804. 

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