WATER ON TAP

what you need to know
Office of Water (4601)

EPA 816-K-03-007

www.epa.gov/safewater

October 2003 Printed on Recycled Paper

Table of Contents

Chapter Page No.

1. A Consumer’s Guide To The Nation’s Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . .1

2. How Safe Is My Drinking Water? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

3. Where Does My Drinking Water Come From And How Is It Treated? . . . . . . . . . . . . .7

4. How Do We Use Drinking Water In Our Homes? . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

5. What’s Being Done To Improve Water Security? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

6. What Can I Do If There Is A Problem With My Drinking Water? . . . . . . . . . . . . . . . .15

7. How Safe Is The Drinking Water In My Household Well? . . . . . . . . . . . . . . . . . . . . .18

8. What You Can Do To Protect Your Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Appendix A: National Primary Drinking Water Standards as of 10/03 . . . . . . . . . . . . . . . . . . . . . . .23

Appendix B: References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Appendix C: Sources of Additional Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Appendix D: Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
The United States enjoys one of the best supplies of 

drinking water in the world. Nevertheless, many of 

us who once gave little or no thought to the water 

that comes from our taps are now asking the question: “Is my water safe to drink?” While tap water 

that meets federal and state standards is generally 

safe to drink, threats to drinking water are increasing. 

Short-term disease outbreaks and water restrictions 

during droughts have demonstrated that we can no 

longer take our drinking water for granted.

Consumers have many questions about their drinking 

water. How safe is my drinking water? What is being 

done to improve security of public water systems? 

Where does my drinking water come from, and how 

is it treated? Do private wells receive the same protection as public water systems? What can I do to 

help protect my drinking water?

1. A Consumer’s Guide To The 

Nation’s Drinking Water

Sensitive Subpopulations

Some people may be more vulnerable to contaminants in drinking water than the general 

population. People undergoing chemotherapy 

or living with HIV/AIDS, transplant patients, 

children and infants, the frail elderly, and pregnant women and their fetuses can be particularly at risk for infections. 

If you have special health care needs, consider taking additional precautions with your 

drinking water, and seek advice from your 

health care provider. For more information, 

see www.epa.gov/safewater/healthcare/

special.html.

You will find information on bottled water 

and home water treatment units on page 16 

of this booklet. You may also contact NSF 

International, Underwriter’s Laboratory, or the 

Water Quality Association. Contact information 

is located in Appendix C.

This booklet provides the answers to these and other 

frequently asked questions. 

This booklet also directs you to more detailed sources 

of information. Often, you will be directed to a page 

on the EPA website. Additionally, the Safe Drinking 

Water Hotline is available to answer your questions. 

Please also see Appendix C for more resources. Refer 

to the Glossary (Appendix D) for definitions of words 

in bold font.

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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

What you need 

to know to protect

your family
2

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

What Law Keeps My Drinking 

Water Safe?

Congress passed the Safe Drinking Water Act 

(SDWA) in 1974 to protect public health by regulating the nation’s public drinking water supply and 

protecting sources of drinking water. SDWA is 

administered by the U.S. Environmental Protection 

Agency (EPA) and its state partners. 

What Is A Public Water System?

The Safe Drinking Water Act (SDWA) defines a 

public water system (PWS) as one that serves piped 

water to at least 25 persons or 15 service connections 

for at least 60 days each year. There are approximately 161,000 public water systems in the United 

States.1 Such systems may be publicly or privately 

owned. Community water systems (CWSs) are 

public water systems that serve people year-round in 

their homes. Most people in the U.S. (268 million) 

get their water from a community water system. EPA 

also regulates other kinds of public water systems, 

2. How Safe Is My Drinking Water?

Highlights of the Safe Drinking 

Water Act

• Authorizes EPA to set enforceable health standards for contaminants in drinking water

• Requires public notification of water systems 

violations and annual reports (Consumer 

Confidence Reports) to customers on contaminants found in their drinking water - 

www.epa.gov/safewater/ccr

• Establishes a federal-state partnership for regulation enforcement

• Includes provisions specifically designed to 

protect underground sources of drinking water 

- www.epa.gov/safewater/uic

• Requires disinfection of surface water supplies, 

except those with pristine, protected sources

• Establishes a multi-billion-dollar state revolving loan fund for water system upgrades - 

www.epa.gov/safewater/dwsrf

• Requires an assessment of the vulnerability of 

all drinking water sources to contamination - 

www.epa.gov/safewater/protect

— Drinking Water: Past, Present, and Future

EPA-816-F-00-002

Public Water Systems

Community Water System (54,000 systems)—

A public water system that serves the same 

people year-round. Most residences are 

served by Community Water Systems.

Non-Community Water System 

(approximately 108,000 systems)—A public 

water system that does not serve the same 

people year-round. There are two types of 

non-community systems:

• Non-Transient Non-Community Water 

System (almost 19,000 systems)—A noncommunity water system that serves the 

same people more than six months of the 

year, but not year-round. For example, a 

school with its own water supply is considered a non-transient system.

• Transient Non-Community Water System 

(more than 89,000 systems)—A noncommunity water system that serves the 

public but not the same individuals for 

more than six months. For example, a rest 

area or a campground may be considered a 

transient system.
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such as those at schools, campgrounds, factories, and 

restaurants. Private water supplies, such as household 

wells that serve one or a few homes, are not regulated 

by EPA. For information on household wells, see 

“How Safe Is The Drinking Water In My Household 

Well?” on page 18 of this booklet.

Will Water Systems Have Adequate 

Funding In The Future?

Nationwide, drinking water systems have spent hundreds of billions of dollars to build drinking water 

treatment and distribution systems. From 1995 to 

2000, more than $50 billion was spent on capital 

investments to fund water quality improvements.2

With the aging of the nation’s infrastructure, the clean 

water and drinking water industries face a significant challenge to sustain and advance their achievements in protecting public health. EPA’s Clean Water 

& Drinking Water Infrastructure Gap Analysis3

has found that if present levels of spending do not 

increase, there will be a significant funding gap by 

the year 2019.

Where Can I Find Information About 

My Local Water System?

Since 1999, water suppliers have been required to 

provide annual Consumer Confidence Reports to 

their customers. These reports are due by July 1 each 

year, and contain information on contaminants found 

in the drinking water, possible health effects, and the 

water’s source. Some Consumer Confidence Reports 

are available at www.epa.gov/safewater/dwinfo.htm.

Water suppliers must promptly inform you if your 

water has become contaminated by something that 

can cause immediate illness. Water suppliers have 

24 hours to inform their customers of violations of 

EPA standards “that have the potential to have serious adverse effects on human health as a result of 

short-term exposure.” If such a violation occurs, the 

water system will announce it through the media, and 

must provide information about the potential adverse 

effects on human health, steps the system is taking to 

correct the violation, and the need to use alternative 

water supplies (such as boiled or bottled water) until 

the problem is corrected.

Systems will inform customers about violations of 

less immediate concern in the first water bill sent 

after the violation, in a Consumer Confidence Report, 

or by mail within a year. In 1998, states began compiling information on individual systems, so you can 

evaluate the overall quality of drinking water in your 

state. Additionally, EPA must compile and summarize 

the state reports into an annual report on the condition of the nation’s drinking water. To view the most 

recent annual report, see www.epa.gov/safewater/annual.

How Often Is My Water Supply 

Tested?

EPA has established pollutant-specific minimum testing schedules for public water systems. To find out 

how frequently your drinking water is tested, contact 

your water system or the agency in your state in 

charge of drinking water. 

If a problem is detected, immediate retesting requirements go into effect along with strict instructions 

about how the system informs the public. Until the 

system can reliably demonstrate that it is free of 

problems, the retesting is continued. 

In 2001, one out of every four community water 

systems did not conduct testing or report the results 

for all of the monitoring required to verify the safety 

Cost of Making Water Safe 

Continues to Rise

Much of the existing water infrastructure 

(underground pipes, treatment plants, and 

other facilities) was built many years ago. In 

1999, EPA conducted the second Drinking 

Water Infrastructure Needs Survey, and found 

that drinking water systems will need to invest 

$150 billion over a 20-year period to ensure 

clean and safe drinking water.
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

of their drinking water.4 Although 

failure to monitor does not necessarily suggest safety problems, conducting the required reporting is crucial to 

ensure that problems will be detected. 

Consumers can help make sure certain 

monitoring and reporting requirements 

are met by first contacting their state 

drinking water agency to determine if 

their water supplier is in compliance. 

If the water system is not meeting the 

requirements, consumers can work with 

local and state officials and the water 

supplier to make sure the required monitoring and reporting occurs.

A network of government agencies 

monitor tap water suppliers and enforce 

drinking water standards to ensure the 

safety of public water supplies. These 

agencies include EPA, state departments of health and environment, 

and local public health departments. Nevertheless, problems with local drinking water can, 

and do, occur.

What Problems Can Occur?

Actual events of drinking water contamination are 

rare, and typically do not occur at levels likely to 

pose health concerns. However, as development in 

our modern society increases, there are growing 

numbers of activities that can contaminate our drinking water. Improperly disposed-of chemicals, animal 

and human wastes, wastes injected underground, and 

naturally occurring substances have the potential to 

contaminate drinking water. Likewise, drinking water 

that is not properly treated or disinfected, or that 

travels through an improperly maintained distribution 

system, may also pose a health risk. Greater vigilance 

by you, your water supplier, and your government 

can help prevent such events in your water supply.

Contaminants can enter water supplies either as a 

result of human and animal activities, or because they 

occur naturally in the environment. Threats to your 

drinking water may exist in your neighborhood, or 

may occur many miles away. For more information 

on drinking water threats, see www.epa.gov/safewater/

District of

Columbia

0% - 6% of Systems 6% - 11% of Systems 11+% of Systems

Reported Community Water Systems Violating

Maximum Contaminant Levels or Treatment 

Standards in FY 2002

Common Sources of Pollution

Naturally Occurring: microorganisms (wildlife and soils), radionuclides (underlying rock), 

nitrates and nitrites (nitrogen compounds in 

the soil), heavy metals (underground rocks 

containing arsenic, cadmium, chromium, lead, 

and selenium), fluoride.

Human Activities: bacteria and nitrates 

(human and animal wastes—septic tanks and 

large farms), heavy metals (mining construction, older fruit orchards), fertilizers and pesticides (used by you and others (anywhere 

crops or lawns are maintained)), industrial 

products and wastes (local factories, industrial plants, gas stations, dry cleaners, leaking underground storage tanks, landfills, and 

waste dumps), household wastes (cleaning 

solvents, used motor oil, paint, paint thinner), 

lead and copper (household plumbing materials), water treatment chemicals (wastewater 

treatment plants).
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

publicoutreach/landscapeposter.html. Some typical 

examples are microbial contamination, chemical contamination from fertilizers, and lead contamination. 

Microbial Contamination:

The potential for health problems from microbialcontaminated drinking water is demonstrated by 

localized outbreaks of waterborne disease. Many of 

these outbreaks have been linked to contamination by 

bacteria or viruses, probably from human or animal 

wastes. For example, in 1999 and 2000, there were 39 

reported disease outbreaks associated with drinking 

water, some of which were linked to public drinking 

water supplies.5

Certain pathogens (disease-causing microorganisms), such as Cryptosporidium, may occasionally 

pass through water filtration and disinfection processes in numbers high enough to cause health problems, 

particularly in vulnerable members of the population. 

Cryptosporidium causes the gastrointestinal disease, 

cryptosporidiosis, and can cause serious, sometimes fatal, symptoms, especially among sensitive 

members of the population. (See box on Sensitive 

Subpopulations on page 1.) A serious outbreak of 

cryptosporidiosis occurred in 1993 in Milwaukee, 

Wisconsin, causing more than 400,000 persons to 

be infected with the disease, and resulting in at least 

50 deaths. This was the largest recorded outbreak of 

waterborne disease in United States history.6

Chemical Contamination From Fertilizers:

Nitrate, a chemical most commonly used as a fertilizer, poses an immediate threat to infants when it is 

found in drinking water at levels above the national 

standard. Nitrates are converted to nitrites in the 

intestines. Once absorbed into the bloodstream, 

nitrites prevent hemoglobin from transporting oxygen. (Older children have an enzyme that restores 

hemoglobin.) Excessive levels can cause “blue baby 

syndrome,” which can be fatal without immediate 

medical attention. Infants most at risk for blue baby 

syndrome are those who are already sick, and while 

they are sick, consume food that is high in nitrates 

or drink water or formula mixed with water that is 

high in nitrates. Avoid using water with high nitrate 

levels for drinking. This is especially important for 

infants and young children, nursing mothers, pregnant 

women and certain elderly people.

Boil Water Notices 

for Microbial 

Contaminants

When microorganisms such 

as those that indicate fecal contamination are 

found in drinking water, water suppliers are 

required to issue “Boil Water Notices.” Boiling 

water for one minute kills the microorganisms that cause disease. Therefore, these 

notices serve as a precaution to the public. 

www.epa.gov/safewater/faq/emerg.html

Nitrates: 

Do NOT Boil

Do NOT boil water to 

attempt to reduce nitrates. 

Boiling water contaminated with nitrates 

increases its concentration and potential risk. 

If you are concerned about nitrates, talk to 

your health care provider about alternatives to 

boiling water for baby formula.

Excessive levels of nitrates

can cause 

“blue baby syndrome,” 

which can be fatal 

without 

immediate 

medical attention.
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Lead Contamination:

Lead, a metal found in natural deposits, is commonly 

used in household plumbing materials and water 

service lines. The greatest exposure to lead is swallowing lead paint chips or breathing in lead dust. 

But lead in drinking water can also cause a variety 

of adverse health effects. In 

babies and children, exposure 

to lead in drinking water 

above the action level of lead 

(0.015 milligram per liter)

can result in delays in physical and mental development, 

along with slight deficits 

in attention span and learning abilities. Adults who 

drink this water over many 

years could develop kidney 

problems or high blood pressure. Lead is rarely found 

in source water, but enters 

tap water through corrosion 

of plumbing materials. Very 

old and poorly maintained 

homes may be more likely 

to have lead pipes, joints, 

and solder. However, new 

homes are also at risk: pipes 

legally considered to be “lead-free” may contain up 

to eight percent lead. These pipes can leach significant amounts of lead in the water for the first several 

months after their installation. For more information 

on lead contamination, see www.epa.gov/safewater/contaminants/dw_contamfs/lead.html.

For more information on drinking water contaminants 

that are regulated by EPA, see Appendix A, or visit 

www.epa.gov/safewater/mcl.html. 

Where Can I Find More Information 

About My Drinking Water?

Drinking water varies from 

place to place, depending on the 

water’s source and the treatment 

it receives. If your drinking water 

comes from a community water 

system, the system will deliver 

to its customers annual drinking 

water quality reports (or Consumer 

Confidence Reports). These 

reports will tell consumers what 

contaminants have been detected 

in their drinking water, how these 

detection levels compare to drinking water standards, and where 

their water comes from. The 

reports must be provided annually 

before July 1, and, in most cases, 

are mailed directly to customers’ 

homes. Contact your water supplier to get a copy of your report, or 

see if your report is posted online 

at www.epa.gov/safewater/dwinfo.htm. Your state’s 

department of health or environment 

can also be a valuable source of information. For 

help in locating these agencies, call the Safe Drinking 

Water Hotline. Further resources can be found in 

Appendix C. Information on testing household wells 

is on page 19.

1 Factoids: Drinking Water & Ground Water Statistics for 

2002, 2003.

2 Community Water Systems Survey 2000, Volume I, 2001.

3 The Clean Water and Drinking Water Infrastructure Gap 

Analysis, EPA 816-R-02-020.

4 Factoids: Drinking Water and Ground Water Statistics for 

2001, EPA 816-K-02-004.

5 Morbidity and Mortality Weekly Report: Surveillance for 

Waterborne Disease Outbreaks, United States 1999-2000, 

2002.

6 25 Years of the Safe Drinking Water Act, 1999.

Lead: Do NOT Boil

Do NOT boil water to attempt 

to reduce lead. Boiling water 

increases lead concentration. 

Always use water from the cold tap for preparing baby formula, cooking, and drinking. 

Flush pipes first by running the water before 

using it. Allow the water to run until it’s cold. 

If you have high lead levels in your tap water, 

talk to your health care provider about alternatives to using boiled water in baby formula.
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Your drinking water comes from surface water or 

ground water. The water that systems pump and 

treat from sources open to the atmosphere, such 

as rivers, lakes, and reservoirs is known as surface 

water. Water pumped from wells drilled into underground aquifers, geologic formations containing 

water, is called ground water. The quantity of water 

produced by a well depends on the nature of the rock, 

sand, or soil in the aquifer from which the water is 

drawn. Drinking water wells may be shallow (50 feet 

or less) or deep (more than 1,000 feet). More water 

systems have ground water than surface water as a 

source (approx. 147,000 v. 14,500), but more people 

drink from a surface water system (195 million v. 

101,400). Large-scale water supply systems tend to 

rely on surface water resources, while smaller water 

systems tend to use ground water. Your water utility 

or public works department can tell you the source of 

your public water supply.

How Does Water Get To 

My Faucet?

An underground network of pipes typically delivers 

drinking water to the homes and businesses served by 

the water system. Small systems serving just a handful of households may be relatively simple, while 

large metropolitan systems can be extremely complex—sometimes consisting of thousands of miles of 

pipes serving millions of people. Drinking water must 

meet required health standards when it leaves the 

treatment plant. After treated water leaves the plant, it 

is monitored within the distribution system to identify 

and remedy any problems such as water main breaks, 

pressure variations, or growth of microorganisms.

How Is My Water Treated 

To Make It Safe?

Water utilities treat nearly 34 billion gallons of water 

every day.1 The amount and type of treatment applied 

varies with the source and quality of the water. 

Generally, surface water systems require more treatment than ground water systems because they are 

directly exposed to the atmosphere and runoff from 

rain and melting snow.

Water suppliers use a variety of treatment processes 

to remove contaminants from drinking water. These 

individual processes can be arranged in a “treatment 

train” (a series of processes applied in a sequence). 

The most commonly used processes include coagulation (flocculation and sedimentation), filtration, 

and disinfection. Some water systems also use ion 

exchange and adsorption. Water utilities select the 

treatment combination most appropriate to treat the 

contaminants found in the source water of that particular system.

Coagulation (Flocculation & Sedimentation): 

Flocculation: This step removes dirt and other particles suspended in the water. Alum and iron salts or 

synthetic organic polymers are added to the water to 

form tiny sticky particles called “floc,” which attract 

the dirt particles.

3. Where Does My Drinking Water 

Come From And How Is It Treated?

All sources of drinking water contain some 

naturally occurring contaminants. At low levels, 

these contaminants generally are not harmful in 

our drinking water. Removing all contaminants 

would be extremely expensive, and in most 

cases, would not provide increased protection 

of public health. A few naturally occurring minerals may actually improve the taste of drinking 

water and may even have nutritional value at 

low levels.
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Sedimentation: The flocculated particles then settle 

naturally out of the water.

Filtration: 

Many water treatment facilities use filtration to 

remove all particles from the water. Those particles 

include clays and silts, natural organic matter, precipitates from other treatment processes in the facility, 

iron and manganese, and microorganisms. Filtration 

clarifies the water and enhances the effectiveness of 

disinfection.

Storage: Water is placed in 

a closed tank or reservoir 

for disinfection to take 

place. The water then flows 

through pipes to homes 

and businesses in the 

community.

Source: AWWA Drinking Water Week Blue Thumb Kit

Filtration: The water passes 

through filters, some made 

of layers of sand, gravel, and 

charcoal that help remove 

even smaller particles.

Sedimentation: 

The heavy particles 

(floc) settle to the 

bottom and the 

clear water moves 

to filtration.

Disinfection: A small amount of chlorine is added or 

some other disinfection method is used to kill any 

bacteria or microorganisms that may be in the water.

Coagulation removes dirt and other particles suspended in 

water. Alum and other chemicals are added to water to form 

tiny sticky particles called “floc” which attract the dirt 

particles. The combined weight of the dirt and the alum 

(floc) become heavy enough to sink to the bottom during 

sedimentation.

Lake or Reservoir

Water Treatment Plant

Follow a drop of water from the source through the treatment process. Water may be treated differently 

in different communities depending on the quality of the water which enters the plant. Groundwater is 

located underground and typically requires less treatment than water from lakes, rivers, and streams.
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Disinfection Byproducts

Disinfection of drinking water is one of the 

major public health advances of the 20th 

century. However, sometimes the disinfectants themselves can react with naturally 

occurring materials in the water to form 

unintended byproducts, which may pose 

health risks. EPA recognizes the importance 

of removing microbial contaminants while 

simultaneously protecting the public from 

disinfection byproducts, and has developed 

regulations to limit the presence of these 

byproducts. For more information, see 

www.epa.gov/safewater/mdbp.html.

Disinfection:

Disinfection of drinking water is considered to be 

one of the major public health advances of the 20th 

century. Water is often disinfected before it enters the 

distribution system to ensure that dangerous microbial contaminants are killed. Chlorine, chlorinates, or 

chlorine dioxides are most often used because they 

are very effective disinfectants, and residual concentrations can be maintained in the water system.

Why Is My Water Bill Rising?

The cost of drinking water is rising as suppliers meet 

the needs of aging infrastructure, comply with public health standards, and expand service areas. In 

most cases, these increasing costs have caused water 

suppliers to raise their rates. However, despite rate 

increases, water is generally still a bargain compared 

to other utilities, such as electricity and phone service. In fact, in the United States, combined water 

and sewer bills average only about 0.5 percent of 

household income.2

1 Protect Your Drinking Water, 2002.

2 Congressional Budget Office Study: Future Investment in 

Drinking Water & Wastewater Infrastructure, 2002.

Water System Filtration Tank

Water passes through charcoal, sand, and 

gravel layers in a water system’s filtration tank. 
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

We take our water supplies for granted, yet they are 

limited. Only one percent of all the world’s water 

can be used for drinking. Nearly 97 percent of the 

world’s water is salty or otherwise undrinkable, and 

the other two percent is locked away in ice caps 

and glaciers. There is no “new” water: whether our 

source water is a stream, river, lake, spring, or well, 

we are using the same water the dinosaurs used millions of years ago.

The average American uses about 90 gallons of water 

each day in the home, and each American household 

uses approximately 107,000 gallons of water each 

year.1 For the most part, we use water treated to meet 

drinking water standards to flush toilets, water lawns, 

and wash dishes, clothes, and cars. In fact, 50-70 

percent of home water is used for watering lawns 

and gardens.2 Nearly 14 percent of the water a typical homeowner pays for is never even used—it leaks 

down the drain.3

How Much Water Do Homes In 

The U.S. Use Compared To Other 

Countries?

Americans use much more water each day than individuals in both developed and undeveloped countries: 

For example, the average European uses 53 gallons; 

the average Sub-Saharan citizen, 3-5 gallons.4

Water efficiency plays an important role in protecting water sources and improving water quality. By 

using water wisely, we can save 

money and help the environment. 

Water efficiency means using less 

water to provide the same benefit. 

Using water-saving techniques 

could save you hundreds of dollars 

each year, while also reducing the 

amount of pollutants entering our 

waterways.

How Do Drinking 

Water Utilities 

Conserve Water?

Water utilities forecast water 

source availability, growth in 

population, and water demand to 

ensure adequate future water supplies during normal 

conditions, as well as periods of drought. When water 

shortages are predicted or experienced, water utilities 

have many options for conserving water. Temporary 

cutbacks or permanent operating adjustments can 

help conserve water.

Temporary cutbacks may include:

• Reduction of system-wide operating pressure, and

• Water use bans, restrictions, and rationing.

4. How Do We Use Drinking 

Water In Our Homes?

Common Household Uses of Drinking Water*

(*Gallons per Capita per Day)

Bathing, 20 gpcd

Toilet Flushing, 24 gpcd

Laundry

8.5 gpcd

Drinking and Cooking, 2 gpcd

Garbage Disposal, 1 gpcd

Dishwasher, 4 gpcd

Car

Washing

2.5 gpcd

Lawn Watering and 

Pools, 25 gpcd Source: Van Der Leeden, F., F. L. Troise, and D. K. Todd.

The Water Encyclopedia. Lewis Publishers, Inc. Second Edition, 1990.
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Permanent conservation measures may include:

• Subsidizing use of water-efficient faucets, toilets, 

and showerheads,

• Public education and voluntary use reduction,

• Billing practices that impose higher rates for higher amounts of water use,

• Building codes that require water-efficient fixtures 

and appliances,

• Leak detection surveys and meter testing, repair, 

and replacement, and

• Reduction in use and increase in recycling of 

industrial water.

How Can Businesses Conserve 

Water?

The industrial and commercial sectors can conserve water through recycling and waste reduction. 

Industry has implemented conservation measures to 

comply with state and federal water pollution controls. Evaluation of industrial plant data may show 

that a particular process or manufacturing step uses 

the most water or causes the greatest contamination. 

Such areas can be targeted for water conservation. 

Also, water that is contaminated by one process may 

be usable in other plant processes that do not require 

high-quality water.

How Can I Conserve Water?

The national average cost of water is $2.00 per 

1,000 gallons. The average American family spends 

about $474 each year on water and sewage charges.5

American households spend an additional $230 per 

year on water heating costs.6 By replacing appliances 

such as the dishwasher and inefficient fixtures such 

as toilets and showerheads, you can save a substantial 

amount each year in water, sewage, and energy costs.

There are many ways to save water in and around 

your home. Here are the five that might get the best 

results:

Ways To Save Water At Home*

(*Water Savings as Percent of Total Interior Water Use)

Low-Flow Showerheads

(or Flow Restrictors), 12 percent

Source: Corbitt, Robert A.

Standard Handbook of Environmental Engineering.

McGraw-Hill, Inc. 1989.

Low-Water Use

Clothes Washers, 5 percent

Low-Water Use Toilets

(or Plastic Bottles or Water Dams 

in Toilet Reservoir), 18 percent

Low-Flow Aerators on 

Faucets (or Replacement 

Faucets), 2 percent

Low-Water Use

Dishwasher, 4 percent

Insulation on

Hot Water Lines, 

4 percent
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www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

• Stop Leaks.

• Replace Old Toilets with models that use 1.6 

gallons or less per flush.

• Replace Old Clothes Washers with EPA Energy 

Star certified models.

• Plant the Right Kind of Garden that requires less 

water.

• Provide Only the Water Plants Need.

For more information on ways to conserve water in 

the home, see www.epa.gov/water/waterefficiency.html or 

www.h2ouse.org. 

1 Water Trivia Facts, EPA 80-F-95-001.

2 AWWA Stats on Tap.

3 Using Water Wisely in the Home, 2002.

4 The Use of Water Today, World Water Council.

5 Investing in America’s Water Infrastructure, 2002.

6 Using Water Wisely in the Home, 2002.

Nearly 14 percent 

of the water 

a typical homeowner 

pays for 

is never even used—

it leaks down 

the drain.

 Using Water Wisely in the Home, 2002
13

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

What Security Measures Are In 

Place To Protect Water Systems?

Drinking water utilities today find themselves facing new responsibilities due to concerns over water 

system security and counter-terrorism. EPA is committed to the safety of public drinking water supplies 

and has taken numerous steps to work with utilities, 

other government agencies, and law enforcement to 

minimize threats.

The Public Health Security and Bioterrorism 

Preparedness and Response Act of 2002 requires that 

all community water systems serving more than 3,300 

people evaluate their susceptibility to potential threats 

and identify corrective actions. EPA has provided 

assistance to help utilities with these Vulnerability 

Assessments by giving direct grants to large systems, 

supporting self-assessment tools, and providing technical help and training to small and medium utilities. 

For more information on water system security, see 

www.epa.gov/safewater/security.

How Can I Help Protect My 

Drinking Water?

Local drinking water and wastewater systems may 

be targets for terrorists and other would-be criminals 

wishing to disrupt and cause harm to your community 

water supplies or wastewater facilities.

Because utilities are often located in isolated areas, 

drinking water sources and wastewater collection systems may cover large areas that are difficult to secure 

and patrol. Residents can be educated to notice and 

report any suspicious activity in and around local 

water utilities. Any residents interested in protecting 

their water resources and community as a whole 

can join together with law enforcement, neighborhood watch groups, water suppliers, wastewater 

operators, and other local public health officials. 

If you witness suspicious activities, report them to 

your local law enforcement authorities.

Examples of suspicious activity might include:

• People climbing or cutting a utility fence

• People dumping or discharging material to a 

water reservoir

5. What’s Being Done To Improve 

Water Security?
14

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Do not confront strangers. Instead report 

suspicious activities to local authorities.

When reporting an incident:

• State the nature of the incident

• Identify yourself and your location

• Identify location of activity

• Describe any vehicle involved (color, make, 

model, plate number)

• Describe the participants (how many, sex, race, 

color of hair, height, weight, clothing)

For more information on water security, visit: 

www.epa.gov/safewater/security

• Unidentified truck or car parked or loitering near 

waterway or facilities for no apparent reason

• Suspicious opening or tampering with manhole 

covers, fire hydrants, buildings, or equipment

• People climbing or on top of water tanks

• People photographing or videotaping utility 

facilities, structures or equipment

• Strangers hanging around locks or gates

Report suspicious 

activity to local 

authorities

For emergencies, dial

9-1-1 or other local 

emergency response 

numbers.
15

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Local incidents, such as spills and treatment problems, can lead to short-term needs for alternative 

water supplies or in-home water treatment. In isolated 

cases, individuals may need to rely on alternative 

sources for the long term, due to their individual 

health needs or problems with obtaining new drinking 

water supplies.

What Alternative Sources Of Water 

Are Available?

Bottled water is sold in supermarkets and convenience stores. Some companies lease or sell water 

dispensers or bubblers and regularly deliver large 

bottles of water to homes and businesses. It is expensive compared to water from a public water system. 

The bottled water quality varies among brands, 

because of the variations in the source water used, 

costs, and company practices.

The U.S. Food and Drug Administration (FDA) regulates bottled water used for drinking. While most consumers assume that bottled water is at least as safe 

as tap water, there are still potential risks. Although 

required to meet the same safety standards as public 

water supplies, bottled water does not undergo the 

same testing and reporting as water from a treatment 

facility. Water that is bottled and sold in the same 

state may not be subject to any federal standards at 

all. Those with compromised immune systems may 

want to read bottled water labels to make sure more 

stringent treatments have been used, such as reverse 

osmosis, distillation, UV radiation, or filtration by an 

absolute 1 micron filter. 

Check with NSF International to see if your bottled 

water adheres to FDA and international drinking 

water standards. The International Bottled Water 

Association can also provide information on which 

brands adhere to even more stringent requirements. 

Contact information is listed in Appendix C.

Can I Do Anything In My House To 

Improve The Safety Of My Drinking 

Water?

Most people do not need to treat drinking water in 

their home to make it safe. However, a home water 

treatment unit can improve water’s taste, or provide 

a factor of safety for those people more vulnerable 

to waterborne disease. There are different options 

for home treatment systems. Point-of-use (POU) 

systems treat water at a single tap. Point-of-entry 

(POE) systems treat water used throughout the house. 

POU systems can be installed in various places in 

the home, including the counter top, the 

faucet itself, or under the sink. POE systems 

are installed where the water line enters the 

house.

POU and POE devices are based on various 

contaminant removal technologies. Filtration, 

ion exchange, reverse osmosis, and distillation are some of the treatment methods used. 

All types of units are generally available 

from retailers, or by mail order. Prices can 

reach well into the hundreds and sometimes 

thousands of dollars, and depending on the 

method and location of installation, plumbing 

can also add to the cost.

6. What Can I Do If There Is A Problem 

With My Drinking Water?
16

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Activated carbon filters adsorb organic contaminants that cause taste and odor problems. Depending 

on their design, some units can remove chlorination 

byproducts, some cleaning solvents, and pesticides. 

To maintain the effectiveness of these units, the carbon canisters must be replaced periodically. Activated 

carbon filters are efficient in removing metals such 

as lead and copper if they are designed to absorb or 

remove lead.

Because ion exchange units can be used to remove 

minerals from your water, particularly calcium and 

magnesium, they are sold for water softening. Some 

ion exchange softening units remove radium and barium from water. Ion exchange systems that employ 

activated alumina are used to remove fluoride and 

arsenate from water. These units must be regenerated 

periodically with salt.

Reverse osmosis treatment units generally remove a 

more diverse list of contaminants than other systems. 

They can remove nitrates, sodium, other dissolved 

inorganics, and organic compounds.

Distillation units boil water and condense the resulting steam to create distilled water. Depending on 

their design, some of these units may allow vaporized 

organic contaminants to condense back into the product water, thus minimizing the removal of organics.

You may choose to boil your water to remove microbial contaminants. Keep in mind that boiling reduces 

TREATMENT DEVICE WHAT IT DOES TO WATER TREATMENT LIMITATIONS

Activated Carbon Filter

(includes mixed media that 

remove heavy metals)

 Adsorbs organic contaminants that 

cause taste and odor problems.

 Somedesigns remove chlorination 

byproducts;

 Some types remove cleaning solvents 

and pesticides

Is efficient in removing metals such 

as lead and copper

Does not remove nitrate, bacteria or 

dissolved minerals

Ion Exchange Unit

(with activated alumina)

 Removes minerals, particularly calcium 

and magnesium that make water “hard”

 Some designs remove radium and 

barium

 Removes fluoride

If water has oxidized iron or iron 

bacteria, the ion-exchange resin will 

become coated or clogged and lose 

its softening ability

Reverse Osmosis Unit

(with carbon)

 Removes nitrates, sodium, other 

dissolved inorganics and organic 

compounds

 Removes foul tastes, smells or colors

 May also reduce the level of some 

pesticides, dioxins and chloroform and 

petrochemicals

Does not remove all inorganic and 

organic contaminants

Distillation Unit Removes nitrates, bacteria, sodium, 

hardness, dissolved solids, most 

organic compounds, heavy metals, and 

radionucleides

 Kills bacteria

Does not remove some volatile 

organic contaminants, certain pesticides and volatile solvents

Bacteria may recolonize on the cooling coils during inactive periods
17

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

the volume of water by about 20 percent, thus concentrating those contaminants not affected by the 

temperature of boiling water, such as nitrates and 

Maintaining Treatment Devices

All POU and POE treatment units need maintenance to operate effectively. If they are not 

maintained properly, contaminants may accumulate in the units and actually make your 

water worse. In addition, some vendors may 

make claims about their effectiveness that 

have no merit. Units are tested for their safety 

and effectiveness by two organizations, NSF 

International and Underwriters Laboratory. 

In addition, the Water Quality Association 

represents the household, commercial, industrial and small community treatment industry 

and can help you locate a professional that 

meets their code of ethics. EPA does not test 

or certify these treatment units.

pesticides. For more information on boiling water, see 

page 5 of this booklet.

No one unit can remove everything. Have your water 

tested by a certified laboratory prior to purchasing 

any device. Do not rely on the tests conducted by 

salespeople that want to sell you their product.

Where Can I Learn More About 

Home Treatment Systems?

Your local library has articles, such as those found 

in consumer magazines, on the effectiveness of these 

devices.

The U.S. General Accounting Office published 

a booklet called Drinking Water: Inadequate 

Regulation of Home Treatment Units Leaves 

Consumers At Risk (December 1991). To read this 

booklet, visit www.gao.gov and search for document 

number RCED-92-34, or call (202) 512-6000.

This treatment device is 

for point of use (POU).

For more information on 

different types of devices contact 

NSF International, 

Underwriters Laboratory, or the 

Water Quality Association 

See Appendix C for 

contact information.
18

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

EPA regulates public water systems; it does not have 

the authority to regulate private wells. Approximately 

15 percent of Americans rely on their own private drinking water supplies (Drinking Water from 

Household Wells, 2002), and these supplies are not 

subject to EPA standards. Unlike public drinking 

water systems serving many people, they do not have 

experts regularly checking the water’s source and its 

quality before it is sent to the tap. These households 

must take special precautions to ensure the protection 

and maintenance of their drinking water supplies.

Drinking Water from Household Wells is an EPA 

publication available to specifically address special 

concerns of a private drinking water supply. To learn 

more, or to obtain a copy, visit www.epa.gov/safewater/

privatewells, or call the Safe Drinking Water Hotline.

How Much Risk Can I Expect?

The risk of having problems depends on how good 

your well is—how well it was built and located, 

and how well you 

maintain it. It also 

depends on your 

local environment. 

That includes the 

quality of the aquifer from which your 

water is drawn and 

the human activities 

going on in your 

area that can affect 

your well.

Several sources of 

pollution are easy to 

spot by sight, taste, or smell. However, many serious 

problems can be found only by testing your water. 

Knowing the possible threats in your area will help 

you decide the kind of tests you may need.

What Should I Do?

There are six basic steps you can take to help protect 

your private drinking water supply:

1. Identify potential problem sources.

2. Talk with local experts.

3. Have your water tested periodically.

4. Have the test results interpreted and explained 

clearly.

5. Set and follow a regular maintenance schedule 

for your well, and keep up-to-date records.

6. Immediately remedy any problems.

Identify Potential Problem Sources

Understanding and spotting possible pollution sources 

is the first step to safeguarding your drinking water. 

If your drinking water comes from a well, you may 

also have a septic system. Septic systems and other 

on-site wastewater disposal systems are major potential sources 

of contamination of private water 

supplies if they are poorly maintained or located improperly, or if 

they are used for disposal of toxic 

chemicals. Information on septic 

systems is available from local 

health departments, state agencies, and the National Small Flows 

Clearinghouse (www.epa.gov/owm/

mab/smcomm/nsfc.htm) at (800) 

624-8301. A septic system design 

manual and guidance on system 

maintenance are available from EPA (www.epa.gov/

OW-OWM.html/mtb/decent/homeowner.htm). 

7. How Safe Is The Drinking Water 

In My Household Well?
19

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Talk With Local Experts

Ground water conditions vary greatly from place to 

place, and local experts can give you the best information about your drinking water supply. Some 

examples are your health department’s “sanitarian,” 

local water-well contractors, public water system 

officials, county extension agents of the Natural 

Resources Conservation Service (NRCS), local or 

county planning commissions, and your local library.

Have Your Water Tested Periodically

Test your water every year for total coliform bacteria, 

nitrates, total dissolved solids, and pH levels. If you 

suspect other contaminants, test for these as well. 

As the tests can be expensive, limit them to possible 

problems specific to your situation. Local experts 

can help you identify these contaminants. You should 

also test your water after replacing or repairing any 

part of the system, or if you notice any change in 

your water’s look, taste, or smell.

Often, county health departments perform tests for 

bacteria and nitrates. For other substances, health 

departments, environmental offices, or county governments should have a list of state-certified laboratories. Your State Laboratory Certification Officer 

can also provide you with this list. Call the Safe 

Drinking Water Hotline for the name and number of 

your state’s certification officer. Any laboratory you 

use should be certified to do drinking water testing.

Have Your Test Results Interpreted And 

Explained Clearly

Compare your well’s test results to federal and 

state drinking water standards (see Appendix A, or 

visit www.epa.gov/safewater/mcl.html or call the Safe 

Drinking Water Hotline). You may need to consult 

experts to aid you in understanding your results, such 

as the state agency that licenses water well contractors, your local health department, or your state’s 

drinking water program.

Protecting Your Ground Water 

Supply

• Periodically inspect exposed parts of the 

well for problems such as:

- Cracked, corroded, or damaged well 

casing

- Broken or missing well cap

- Settling and cracking of surface seals.

• Slope the area around the well to drain surface runoff away from the well.

• Install a well cap or sanitary seal to prevent 

unauthorized use of, or entry into, the well.

• Disinfect drinking water wells at least once 

per year with bleach or hypochlorite granules, according to the manufacturer’s directions.

• Have the well tested once a year for coliform bacteria, nitrates, and other constituents of concern.

• Keep accurate records of any well maintenance, such as disinfection or sediment 

removal, that may require the use of chemicals in the well.

• Hire a certified well driller for any new well 

construction, modification, or abandonment and closure.

• Avoid mixing or using pesticides, fertilizers, 

herbicides, degreasers, fuels, and other 

pollutants near the well.

• Do not dispose of wastes in dry wells or in 

abandoned wells.

• Do not cut off the well casing below the 

land surface.

• Pump and inspect septic systems as often 

as recommended by your local health 

department.

• Never dispose of hazardous materials in a 

septic system.
20

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Set A Regular Maintenance Schedule For 

Your Well And Your Septic System

Proper well and septic system construction and continued maintenance are keys to the safety of your 

water supply. Your state water well and septic system 

contractor licensing agency, local health department, 

or local public water system professional can provide 

information on well construction. Make certain your 

contractors are licensed by the state, if required, or 

certified by the National Ground Water Association.

Maintain your well, fixing problems before they 

reach crisis levels, and keep up-to-date 

records of well installation and repairs, as 

well as plumbing and water costs. Protect 

your own well area from contamination.

Immediately Remedy Any 

Problems

If you find that your well water is contaminated, fix the problem as soon as 

possible. Consider connecting into a 

nearby community water system, if one is 

available. You may want to install a water 

treatment device to remove impurities. 

Information on these devices is provided 

on page 16. If you connect to a public water system, 

remember to close your well properly.

After A Flood-Concerns And Advisories

• Stay away from well pump to avoid electric shock.

• Do not drink or wash from a flooded well.

• Pump the well until water runs clear.

• If water does not run clear, contact the county or 

state health department or extension service for 

advice.

Animal waste

can

contaminate

your 

water supply
21

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Drinking water protection is a shared responsibility. 

Many actions are underway to protect our nation’s 

drinking water, and there are many opportunities for 

citizens to become involved.

Be Involved!

EPA activities to protect drinking water include setting drinking water standards and overseeing the 

work of states that enforce federal standards—or 

stricter ones set by the individual state. EPA holds 

many public meetings on issues ranging from proposed drinking water standards to the development of 

databases. You can also comment on proposed drafts 

of other upcoming EPA documents. A list of public 

meetings and regulations open for comment can be 

found at www.epa.gov/safewater/pubinput/html. 

Be Informed!

• Read the annual Consumer Confidence Report 

provided by your water supplier. Some Consumer 

Confidence Reports are available at www.epa.gov/

safewater/dwinfo.htm. 

• Use information from your state’s Source Water 

Assessment to learn about potential threats to your 

water source.

• If you are one of the 15 percent of Americans who 

uses a private source of drinking water—such as 

a well, cistern, or spring—find out what activities are taking place in your watershed that may 

impact your drinking water; talk to local experts/

test your water periodically; and maintain your 

well properly.

• Find out if the Clean Water Act standards for your 

drinking water source are intended to protect water 

for drinking, in addition to fishing and swimming.

Be Observant!

• Look around your watershed and look for 

announcements in the local media about activities 

that may pollute your drinking water.

• Form and operate a citizens watch network within your community to communicate regularly with 

law enforcement, your public water supplier and 

wastewater operator. Communication is key to a 

safer community!

• Be alert. Get to know your water/wastewater utilities, their vehicles, routines and their personnel.

• Become aware of your surroundings. This 

will help you to recognize suspicious activity as 

opposed to normal daily activities.

Other Ways To Get Involved

• Attend public hearings on new construction, storm water permitting, and town 

planning.

• Keep your public officials accountable by 

asking to see their environmental impact 

statements.

• Ask questions about any issue that may 

affect your water source.

• Participate with your government and your 

water system as they make funding decisions.

• Volunteer or help recruit volunteers to participate in your community’s contaminant 

monitoring activities.

• Help ensure that local utilities that protect 

your water have adequate resources to do 

their job. 

8. What You Can Do To Protect Your 

Drinking Water
22

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

• If you see any suspicious activities in or around 

your water supply, please notify local authorities or 

call 9-1-1 immediately to report the incident.

Don’t Contaminate!

• Reduce paved areas: use 

permeable surfaces that allow rain to 

soak through, not run off.

• Reduce or eliminate pesticide 

application: test your soil before 

applying chemicals, and use plants 

that require little or no water, pesticides, or fertilizers.

• Reduce the amount of trash 

you create: reuse and recycle.

• Recycle used oil: 1 quart of 

oil can contaminate 2 million gallons 

of drinking water—take your used oil and antifreeze to a service station or recycling center.

• Take the bus instead of your car one day a week: 

you could prevent 33 pounds of carbon dioxide 

emissions each day.

• Keep pollutants away from boat marinas and 

waterways: keep boat motors well-tuned to prevent 

leaks, select nontoxic cleaning products and use 

a drop cloth, and clean and maintain boats away 

from the water.

For more information on how you can help protect your local drinking water source, call the Safe 

Drinking Water Hotline, or check www.epa.gov/

safewater/publicoutreach. Additional resources are 

listed in Appendix C.

Stormwater runoff threatens our sources of 

drinking water. As this water washes over 

roofs, pavement, farms and grassy areas, it 

picks up fertilizers, pesticides and litter, and 

deposits them in surface water and ground 

water. Here are some other threats to our 

drinking water:

Every year:

• We apply 67 million pounds of pesticides 

that contain toxic and harmful chemicals to 

our lawns.

• We produce more than 230 million tons of 

municipal solid water—approximately five 

pounds of trash or garbage per person per 

day—that contain bacteria, nitrates, viruses, synthetic detergents, and household 

chemicals.

• Our more than 12 million recreational 

and houseboats and 10,000 boat marinas 

release solvents, gasoline, detergents, and 

raw sewage directly into our rivers, lakes 

and streams.
23

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Appendix A: National Primary Drinking 

Water Standards as of 10/03

Contaminant MCL or TT1

(mg/L)2

Potential health effects from 

exposure above the MCL

Common sources of contaminant 

in drinking water

Public 

Health Goal

OC Acrylamide TT8 Nervous system or blood problems; 

increased risk of cancer 

Added to water during sewage/

wastewater treatment

zero

OC Alachlor 0.002 Eye, liver, kidney or spleen problems; 

anemia; increased risk of cancer

Runoff from herbicide used on row 

crops

zero

R

Alpha particles 15 picocuries per Liter 

(pCi/L)

Increased risk of cancer Erosion of natural deposits of certain 

minerals that are radioactive and 

may emit a form of radiation known 

as alpha radiation

zero

IOC

Antimony 0.006 Increase in blood cholesterol; decrease 

in blood sugar

Discharge from petroleum refineries; 

fire retardants; ceramics; electronics; 

solder

0.006

IOC

Arsenic 0.010 as of 

1/23/06

Skin damage or problems with circulatory systems, and may have increased 

risk of getting cancer

Erosion of natural deposits; runoff 

from orchards; runoff from glass & 

electronics production wastes

0

IOC

Asbestos (fibers >10 

micrometers)

7 million 

fibers per 

Liter (MFL)

Increased risk of developing benign 

intestinal polyps

Decay of asbestos cement in water 

mains; erosion of natural deposits

7 MFL

OC Atrazine 0.003 Cardiovascular system or reproductive 

problems

Runoff from herbicide used on row 

crops

0.003

IOC

Barium 2 Increase in blood pressure Discharge of drilling wastes; discharge from metal refineries; erosion 

of natural deposits

2

OC Benzene 0.005 Anemia; decrease in blood platelets; 

increased risk of cancer

Discharge from factories; leaching 

from gas storage tanks and landfills

zero

OC Benzo(a)pyrene (PAHs) 0.0002 Reproductive difficulties; increased risk 

of cancer

Leaching from linings of water storage tanks and distribution lineszero

IOC

Beryllium 0.004 Intestinal lesions Discharge from metal refineries and 

coal-burning factories; discharge 

from electrical, aerospace, and 

defense industries

0.004

R

Beta particles and photon emitters4 millirems 

per year

Increased risk of cancer Decay of natural and man-made 

deposits of certain minerals that are 

radioactive and may emit forms of 

radiation known as photons and beta 

radiation

zero

DBP Bromate 0.010 Increased risk of cancer Byproduct of drinking water 

disinfection

zero

IOC

Cadmium 0.005 Kidney damage Corrosion of galvanized pipes; 

erosion of natural deposits; discharge 

from metal refineries; runoff from 

waste batteries and paints

0.005

OC Carbofuran 0.04 Problems with blood, nervous system, 

or reproductive system

Leaching of soil fumigant used on 

rice and alfalfa

0.04

OC Carbon tetrachloride 0.005 Liver problems; increased risk of cancer Discharge from chemical plants and 

other industrial activities

zero

D Chloramines (as Cl2) MRDL=4.01 Eye/nose irritation; stomach discomfort; 

anemia

Water additive used to control 

microbes

MRDLG=41
24

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Contaminant MCL or TT1

(mg/L)2

Potential health effects from 

exposure above the MCL

Common sources of contaminant 

in drinking water

Public 

Health Goal

OC Chlordane 0.002 Liver or nervous system problems; 

increased risk of cancer

Residue of banned termiticide zero

D Chlorine (as Cl2) MRDL=4.01 Eye/nose irritation; stomach discomfort Water additive used to control 

microbes 

MRDLG=41

D Chlorine dioxide 

(as ClO2)

MRDL=0.81 Anemia; infants & young children: 

nervous system effects

Water additive used to control 

microbes

MRDLG=0.81

DBP Chlorite 1.0 Anemia; infants & young children: 

nervous system effects

Byproduct of drinking water 

disinfection

0.8

OC Chlorobenzene 0.1 Liver or kidney problems Discharge from chemical and agricultural chemical factories

0.1

IOC Chromium (total) 0.1 Allergic dermatitis Discharge from steel and pulp mills; 

erosion of natural deposits

0.1

IOC

Copper TT7; 

Action 

Level = 

1.3

Short-term exposure: Gastrointestinal 

distress. Long-term exposure: Liver or 

kidney damage. People with Wilson’s 

Disease should consult their personal 

doctor if the amount of copper in their 

water exceeds the action level

Corrosion of household plumbing 

systems; erosion of natural deposits

1.3

M Cryptosporidium TT3 Gastrointestinal illness (e.g., diarrhea, 

vomiting, cramps)

Human and animal fecal waste zero

IOC

Cyanide 

(as free cyanide)

0.2 Nerve damage or thyroid problems Discharge from steel/metal factories; 

discharge from plastic and fertilizer 

factories

0.2

OC 2,4-D 0.07 Kidney, liver, or adrenal gland problems Runoff from herbicide used on row 

crops

0.07

OC Dalapon 0.2 Minor kidney changes Runoff from herbicide used on rights 

of way

0.2

OC

1,2-Dibromo-3-

chloropropane (DBCP)

0.0002 Reproductive difficulties; increased risk 

of cancer

Runoff/leaching from soil fumigant 

used on soybeans, cotton, pineapples, and orchards

zero

OC o-Dichlorobenzene 0.6 Liver, kidney, or circulatory system 

problems

Discharge from industrial chemical 

factories

0.6

OC p-Dichlorobenzene 0.075 Anemia; liver, kidney or spleen damage; 

changes in blood

Discharge from industrial chemical 

factories

0.075

OC 1,2-Dichloroethane 0.005 Increased risk of cancer Discharge from industrial chemical 

factories

zero

OC 1,1-Dichloroethylene 0.007 Liver problems Discharge from industrial chemical 

factories

0.007

OC cis-1,2-Dichloroethylene 0.07 Liver problems Discharge from industrial chemical 

factories

0.07

OC trans-1,2-

Dichloroethylene

0.1 Liver problems Discharge from industrial chemical 

factories

0.1

OC Dichloromethane 0.005 Liver problems; increased risk of cancer Discharge from drug and chemical 

factories

zero

OC 1,2-Dichloropropane 0.005 Increased risk of cancer Discharge from industrial chemical 

factories

zero

OC Di(2-ethylhexyl) adipate 0.4 Weight loss, liver problems, or possible 

reproductive difficulties

Discharge from chemical factories 0.4

OC Di(2-ethylhexyl) 

phthalate

0.006 Reproductive difficulties; liver problems; 

increased risk of cancer

Discharge from rubber and chemical 

factories

zero

OC Dinoseb 0.007 Reproductive difficulties Runoff from herbicide used on soybeans and vegetables

0.007
25

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Contaminant MCL or TT1

(mg/L)2

Potential health effects from 

exposure above the MCL

Common sources of contaminant 

in drinking water

Public 

Health Goal

 OC

Dioxin (2,3,7,8-TCDD) 0.00000003 Reproductive difficulties; increased risk 

of cancer

Emissions from waste incineration 

and other combustion; discharge 

from chemical factories

zero

OC Diquat 0.02 Cataracts Runoff from herbicide use 0.02

OC Endothall 0.1 Stomach and intestinal problems Runoff from herbicide use 0.1

OC Endrin 0.002 Liver problems Residue of banned insecticide 0.002

OC

Epichlorohydrin TT8 Increased cancer risk, and over a long 

period of time, stomach problems

Discharge from industrial chemical 

factories; an impurity of some water 

treatment chemicals

zero

OC Ethylbenzene 0.7 Liver or kidney problems Discharge from petroleum refineries 0.7

OC

Ethylene dibromide 0.00005 Problems with liver, stomach, reproductive system, or kidneys; increased risk 

of cancer

Discharge from petroleum refineries zero

IOC

Fluoride 4.0 Bone disease (pain and tenderness of 

the bones); children may get mottled 

teeth

Water additive which promotes 

strong teeth; erosion of natural 

deposits; discharge from fertilizer 

and aluminum factories

4.0

M Giardia lamblia TT3 Gastrointestinal illness (e.g., diarrhea, 

vomiting, cramps)

Human and animal fecal waste zero

OC Glyphosate 0.7 Kidney problems; reproductive 

difficulties 

Runoff from herbicide use 0.7

DBP Haloacetic acids 

(HAA5) 

0.060 Increased risk of cancer Byproduct of drinking water 

disinfection

n/a6

OC Heptachlor 0.0004 Liver damage; increased risk of cancer Residue of banned termiticide zero

OC Heptachlor epoxide 0.0002 Liver damage; increased risk of cancer Breakdown of heptachlor zero

M

Heterotrophic plate 

count (HPC)

TT3 HPC has no health effects; it is an 

analytic method used to measure the 

variety of bacteria that are common in 

water. The lower the concentration of 

bacteria in drinking water, the better 

maintained the water system is.

HPC measures a range of bacteria 

that are naturally present in the 

environment

n/a

OC Hexachlorobenzene 0.001 Liver or kidney problems; reproductive 

difficulties; increased risk of cancer

Discharge from metal refineries and 

agricultural chemical factories

zero

OC Hexachlorocyclopentadiene

0.05 Kidney or stomach problems Discharge from chemical factories 0.05

IOC

Lead TT7; 

Action 

Level = 

0.015

Infants and children: Delays in physical 

or mental development; children could 

show slight deficits in attention span 

and learning abilities; Adults: Kidney 

problems; high blood pressure

Corrosion of household plumbing 

systems; erosion of natural deposits

zero

M Legionella TT3 Legionnaire’s Disease, a type of 

pneumonia

Found naturally in water; multiplies in 

heating systems

zero

OC Lindane 0.0002 Liver or kidney problems Runoff/leaching from insecticide used 

on cattle, lumber, gardens

0.0002

IOC

Mercury (inorganic) 0.002 Kidney damage Erosion of natural deposits; discharge from refineries and factories; 

runoff from landfills and croplands

0.002

OC Methoxychlor 0.04 Reproductive difficulties Runoff/leaching from insecticide used 

on fruits, vegetables, alfalfa, livestock

0.04
26

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Contaminant MCL or TT1

(mg/L)2

Potential health effects from 

exposure above the MCL

Common sources of contaminant 

in drinking water

Public 

Health Goal

IOC

Nitrate (measured as 

Nitrogen)

10 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 bluebaby syndrome.

Runoff from fertilizer use; leaching 

from septic tanks, sewage; erosion of 

natural deposits

10

IOC

Nitrite (measured as 

Nitrogen)

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 bluebaby syndrome.

Runoff from fertilizer use; leaching 

from septic tanks, sewage; erosion of 

natural deposits

1

OC Oxamyl (Vydate) 0.2 Slight nervous system effects Runoff/leaching from insecticide used 

on apples, potatoes, and tomatoes

0.2

OC Pentachlorophenol 0.001 Liver or kidney problems; increased 

cancer risk

Discharge from wood-preserving 

factories

zero

OC Picloram 0.5 Liver problems Herbicide runoff 0.5

OC

Polychlorinated biphenyls (PCBs)0.0005 Skin changes; thymus gland problems; 

immune deficiencies; reproductive or 

nervous system difficulties; increased 

risk of cancer

Runoff from landfills; discharge of 

waste chemicals 

zero

R Radium 226 and 

Radium 228 (combined)

5 pCi/L Increased risk of cancer Erosion of natural deposits zero

IOC

Selenium 0.05 Hair or fingernail loss; numbness in fingers or toes; circulatory problemsDischarge from petroleum refineries; 

erosion of natural deposits; discharge from mines

0.05

OC Simazine 0.004 Problems with blood Herbicide runoff 0.004

OC Styrene 0.1 Liver, kidney, or circulatory system 

problems

Discharge from rubber and plastic 

factories; leaching from landfills

0.1

OC Tetrachloroethylene 0.005 Liver problems; increased risk of cancer Discharge from factories and dry 

cleaners

zero

IOC

Thallium 0.002 Hair loss; changes in blood; kidney, 

intestine, or liver problems

Leaching from ore-processing sites; 

discharge from electronics, glass, 

and drug factories

0.0005

OC Toluene 1 Nervous system, kidney, or liver 

problems

Discharge from petroleum factories 1

M

Total Coliforms (including fecal coliform and 

E. coli)

5.0 

percent4

Not a health threat in itself; it is used to 

indicate whether other potentially harmful bacteria may be present5

Coliforms are naturally present in the 

environment as well as feces; fecal 

coliforms and E. coli only come from 

human and animal fecal waste

zero

DBP

Total Trihalomethanes 

(TTHMs)

0.10

0.080 

after 12/31/

03

Liver, kidney or central nervous system 

problems; increased risk of cancer

Byproduct of drinking water 

disinfection

n/a6

OC Toxaphene 0.003 Kidney, liver, or thyroid problems; 

increased risk of cancer

Runoff/leaching from insecticide used 

on cotton and cattle

zero

OC 2,4,5-TP (Silvex) 0.05 Liver problems Residue of banned herbicide 0.05

OC 1,2,4-Trichlorobenzene 0.07 Changes in adrenal glands Discharge from textile finishing 

factories

0.07

OC 1,1,1-Trichloroethane 0.2 Liver, nervous system, or circulatory 

problems

Discharge from metal degreasing 

sites and other factories

0.20
27

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Contaminant MCL or TT1

(mg/L)2

Potential health effects from 

exposure above the MCL

Common sources of contaminant 

in drinking water

Public 

Health Goal

OC 1,1,2-Trichloroethane 0.005 Liver, kidney, or immune system 

problems

Discharge from industrial chemical 

factories

0.003

OC Trichloroethylene 0.005 Liver problems; increased risk of cancer Discharge from metal degreasing 

sites and other factories

zero

M

Turbidity TT3 Turbidity is a measure of the cloudiness 

of water. It is used to indicate water 

quality and filtration effectiveness (e.g., 

whether disease-causing organisms 

are present). Higher turbidity levels are 

often associated with higher levels of 

disease-causing microorganisms such 

as viruses, parasites and some bacteria. 

These organisms can cause symptoms 

such as nausea, cramps, diarrhea, and 

associated headaches.

Soil runoff n/a

R

Uranium 30 ug/L 

as of 12/

08/03

Increased risk of cancer, kidney toxicity Erosion of natural deposits zero

OC Vinyl chloride 0.002 Increased risk of cancer Leaching from PVC pipes; discharge 

from plastic factories

zero

M Viruses (enteric) TT3 Gastrointestinal illness (e.g., diarrhea, 

vomiting, cramps)

Human and animal fecal waste zero

OC Xylenes (total) 10 Nervous system damage Discharge from petroleum factories; 

discharge from chemical factories

10

NOTES

1 Definitions

• Maximum Contaminant Level Goal (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 and are non-enforceable public health goals.

• Maximum Contaminant Level (MCL)—The highest level of a contaminant that is 

allowed in drinking water. MCLs are set as close to MCLGs as feasible using the 

best available treatment technology and taking cost into consideration. MCLs are 

enforceable standards.

• Maximum Residual Disinfectant Level Goal (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. 

• Maximum Residual Disinfectant Level (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.

• Treatment Technique (TT)—A required process intended to reduce the level of a 

contaminant in drinking water.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are 

equivalent to parts per million (ppm).

3 EPA’s surface water treatment rules require systems using surface water or ground 

water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants 

are controlled at the following levels:

• Cryptosporidium (as of 1/1/02 for systems serving >10,000 and 1/14/05 for systems 

serving <10,000) 99 percent removal.

• Giardia lamblia: 99.9 percent removal/inactivation

• Viruses: 99.99 percent removal/inactivation

• Legionella: No limit, but EPA believes that if Giardia and viruses are removed/

inactivated, Legionella will also be controlled.

• Turbidity: At no time can turbidity (cloudiness of water) go above 5 nephelolometric 

turbidity units (NTU); systems that filter must ensure that the turbidity go no higher 

than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95 percent 

of the daily samples in any month. As of January 1, 2002, for systems servicing 

>10,000, and January 14, 2005, for systems servicing <10,000, turbidity may never 

exceed 1 NTU, and must not exceed 0.3 NTU in 95 percent of daily samples in any 

month.

• HPC: No more than 500 bacterial colonies per milliliter

• Long Term 1 Enhanced Surface Water Treatment (Effective Date: January 14, 

2005); Surface water systems or (GWUDI) systems serving fewer than 10,000 

people must comply with the applicable Long Term 1 Enhanced Surface Water 

Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, 

Cryptosporidium removal requirements, updated watershed control requirements for 

unfiltered systems).

• Filter Backwash Recycling: The Filter Backwash Recycling Rule requires systems 

that recycle to return specific recycle flows through all processes of the system’s 

existing conventional or direct filtration system or at an alternate location approved 

by the state.

4 No more than 5.0 percent samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample 

can be total coliform-positive per month.) Every sample that has total coliform must be 

analyzed for either fecal coliforms or E. coli. If two consecutive TC-positive samples, 

and one is also positive for E. coli fecal coliforms, system has an acute MCL violation. 

5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may 

be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other 

symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems.

6 Although there is no collective MCLG for this contaminant group, there are individual 

MCLGs for some of the individual contaminants: 

• Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/L)

• Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L)

7 Lead and copper are regulated by a Treatment Technique that requires systems to 

control the corrosiveness of their water. If more than 10 percent of tap water samples 

exceed the action level, water systems must take additional steps. For copper, the 

action level is 1.3 mg/L, and for lead is 0.015 mg/L.

8 Each water system must certify, in writing, to the state (using third-party or manufacturers certification) that when it uses acrylamide and/or epichlorohydrin to treat water, 

the combination (or product) of dose and monomer level does not exceed the levels 

specified, as follows: Acrylamide = 0.05 percent dosed at 1 mg/L (or equivalent); 

Epichlorohydrin = 0.01 percent dosed at 20 mg/L (or equivalent).
28

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

US EPA Publications

25 Years of the Safe Drinking 

Water Act: History & Trends

EPA 816-R-99-007

December 1999

Community Water Systems 

Survey 2000, Volume I

EPA 815-R-02-0054

December 2002

Drinking Water Costs and 

Federal Funding

EPA 810-F-99-014

December 1999

Drinking Water from Household 

Wells

EPA 816-K-02-003

January 2002

Drinking Water Priority 

Rulemaking: Microbial and 

Disinfection Byproduct Rules

EPA 816-F-01-012

June 2001

Drinking Water Treatment

EPA 810-F-99-013

December 1999

Factoids: Drinking Water

and Ground Water Statistics for 

2001

EPA 815-K-02-004

May 2002

Factoids: Drinking Water and 

Ground Water Statistics for 2002

EPA 816–K-03-001

January 2003

Fact Sheet: 1999 Drinking 

Water Infrastructure Needs 

Survey

EPA 816-F-01-001

February 2001 

“Investing in America’s Water 

Infrastructure” Keynote 

Address by G. Tracy Mehan III 

to the Schwab Capital Markets’ 

Global Water Conference

April 2003

Protect Your Drinking Water

EPA 816-F-02-012

September 2002

Public Access to Information & 

Public Involvement

EPA 810-F-99-021

December 1999

Report to Congress: EPA 

Studies on Sensitive 

Subpopulations and Drinking 

Water Contaminants

EPA 815-R-00-015

December 2000

Safe Drinking Water ActProtecting America’s Public 

Health

EPA 816-H-02-003

January 2002

Safe Drinking Water Act: 

Underground Injection Control 

Program: Protecting Public 

Health and Drinking Water 

Resources

EPA 816-H-01-003

August 2001

The Clean Water and Drinking 

Water Infrastructure Gap 

Analysis

EPA 816-F-02-017

September 2002

The Drinking Water State 

Revolving Fund: Protecting the 

Public Through Drinking Water 

Infrastructure Improvements

EPA 819-F-00-028

November 2001

Understanding the Safe Drinking 

Water Act

EPA 810-F-99-008

December 1999

Using Water Wisely in the Home

EPA 800-F-02-001

June 2001

Publications From 

Outside Sources

Centers for Disease Control 

and Prevention. Morbidity 

and Mortality Weekly Report: 

Surveillance for WaterborneDisease Outbreaks-United 

States-1999-2000. 

November 22, 2002 

Congressional Budget 

Office. Future Investment in 

Drinking Water & Wastewater 

Infrastructure

November 2002

Appendix B: References
29

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

American Water Works Association

Public Affairs Department

6666 West Quincy Avenue

Denver, CO 80235

Phone (303) 794-7711

www.awwa.org

Association of Metropolitan Water Agencies

1620 I Street NW

Suite 500

Washington, DC 20006

Phone (202) 331-2820

Fax (202) 785-1845

www.amwa.net

Association of State Drinking Water 

Administrators

1025 Connecticut Avenue NW

Suite 903

Washington, DC 20036

Phone (202) 293-7655

www.asdwa.org

Clean Water Action

4455 Connecticut Avenue NW Suite A300

Washington, DC 20008

Phone (202) 895-0420

www.cleanwater.org

Consumer Federation of America

1424 16th Street NW

Suite 604

Washington, DC 20036

Phone (202) 387-6121

www.consumerfed.org

The Groundwater Foundation

P.O. Box 22558

Lincoln, NE 68542

Phone (800) 858-4844

www.groundwater.org

The Ground Water Protection Council

13308 N. Mac Arthur

OKC, OK 73142

Phone (405) 516-4972

www.gwpc.org

International Bottled Water Association 

1700 Diagonal Road

Suite 650

Alexandria, VA 22314

Phone (703) 683-5213 

Information Hotline 1-800-WATER-11

ibwainfo@bottledwater.org

National Association of Regulatory Utility 

Commissioners

Phone (202) 898-2200

www.naruc.org

National Association of Water Companies

1725 K Street NW

Suite 1212

Washington, DC 20006

Phone (202) 833-8383

www.nawc.org

National Drinking Water Clearinghouse

West Virginia University

P.O. Box 6064

Morgantown, WV 26506

Phone (800) 624-8301

www.ndwc.wvu.edu

National Ground Water Association

601 Dempsey Rd

Westerville, OH 43081-8978

Phone: (800) 551-7379

www.ngwa.org

National Rural Water Association

2915 South 13th Street

Duncan, OK 73533

Phone (580) 252-0629

www.nrwa.org

Natural Resources Defense Council

40 West 20th Street

New York, NY 10011

Phone (212) 727-2700

www.nrdc.org

Appendix C: Sources of Additional 

Information
30

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

NSF International

P.O. Box 130140

789 North Dixboro Road

Ann Arbor, MI 48113

Phone (800) NSF-MARK

www.nsf.org

Rural Community Assistance Program

1522 K Street NW

Suite 400

Washington, DC 20005

Phone (202) 408-1273

www.rcap.org

Underwriters Laboratories

Corporate Headquarters

333 Pfingsten Road

Northbrook, IL 60062-2096

Phone (877) 272-8800

www.ul.com

Water Quality Association

4151 Naperville Road

Lisle, IL 60532

Phone (630) 505-0160

www.wqa.org

U.S. Environmental Protection Agency Water 

Resource Center

1200 Pennsylvania Avenue NW

RC-4100

Washington, DC 20460

SDWA Hotline (800) 426-4791

www.epa.gov/safewater

Water Systems Council

National Programs Office

101 30th Street NW

Suite 500

Washington, D.C. 20007

Phone: (202) 625-4387

Wellcare Hotline 888-395-1033

www.watersystems council.org

EPA Region 1 

(CT, ME, MA, NH, RI, VT)

Phone (617) 918-1111 

Phone (617) 918-1614

(UIC issues)

EPA Region 2

(NJ, NY, PR, VI)

Phone (212) 637-5000

Phone (212) 637-4232

(UIC issues)

EPA Region 3

(DE, DC, MD, PA, VA, WV)

Phone (215) 814-5700

Phone (215) 814-5445

(UIC issues)

EPA Region 4

(AL, FL, GA, KY, MS, NC, SC, TN)

Phone (404) 562-9900

Phone (404) 562-9452

(UIC issues)

EPA Region 5

(IL, IN, MI, MN, OH, WI)

Phone (312) 886-2000

Phone (312) 886-1492

(UIC issues)

EPA Region 6

(AR, LA, NM, OK, TX)

Phone (214) 665-6444

Phone (214) 665-7183

(UIC issues) 

EPA Region 7

(IA, KS, MO, NE)

Phone (913) 551-7003

Phone (913) 551-7030

(UIC issues)

EPA Region 8

(CO, MT, ND, SD, UT, WY)

Phone (303) 312-6312

Phone (303) 312-6242

(UIC issues)

EPA Region 9

(AZ, CA, HI, NW, AS GU)

Phone (415) 947-8000

Phone (415) 947-1834

(UIC issues)

EPA Region 10

(AK, ID, OR, WA)

Phone (206) 553-1200

Phone (206) 553-1901

(UIC issues)
31

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Action Level

The level of lead and copper which, if exceeded, 

triggers treatment or other requirements that a 

water system must follow. 

Aquifer

A natural underground layer, often of sand or 

gravel, that contains water

Coliform

A group of related bacteria whose presence in 

drinking water may indicate contamination by 

disease-causing microorganisms

Community Water System (CWS)

A water system that supplies drinking water to 25 

people or more year-round in their residences

Contaminant

Anything found in water (including microorganisms, radionuclides, chemicals, minerals, etc.) 

which may be harmful to human health

Cryptosporidium

Microorganism found commonly in lakes and rivers 

which is highly resistant to disinfection. 

Disinfectant

A chemical (commonly chlorine, chloramines, or 

ozone) or physical process (e.g., ultraviolet light) 

that kills microorganisms such as viruses, bacteria, 

and protozoa

Distribution System

A network of pipes leading from a treatment plant 

to customers’ plumbing systems

Ground Water

Water that is pumped and treated from an aquifer

Inorganic Contaminants

Mineral-based compounds such as metals, nitrates, 

and asbestos; naturally occurring in some water, 

but can also enter water through human activities 

Maximum Contaminant Level

The highest level of a contaminant that EPA allows 

in drinking water (legally enforceable standard)

Maximum Contaminant Level Goal

The level of a contaminant at which there would be 

no risk to human health (not a legally enforceable 

standard)

Microorganisms

Tiny living organisms that can be seen only under 

a microscope; some can cause acute health problems when consumed in drinking water

Non-Transient Non-Community Water 

System

A non-community water system that serves the 

same people more than six months of the year, but 

not year-round

Organic Contaminants

Carbon-based chemicals, such as solvents and pesticides, which enter water through cropland runoff 

or discharge from factories

Pathogen

Disease-causing organism

Appendix D: Glossary
32

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791

Public Water System (PWS)

A water system which supplies drinking water to at 

least 25 people, at least 60 days each year

Sensitive Subpopulation

People who may be more vulnerable to drinking 

water contamination, such as infants, children, 

some elderly, and people with severely compromised immune systems

Septic System

Used to treat sanitary waste; can be a significant 

threat to water quality due to leaks or runoff

Source Water

Water in its natural state, prior to any treatment for 

drinking (i.e., lakes, streams, ground water)

Surface Water

Water that is pumped and treated from sources 

open to the atmosphere, such as rivers, lakes, and 

reservoirs 

Transient Non-Community Water System

A non-community water system that serves the 

public but not the same individuals for more than 

six months

Violation

Failure to meet any state or federal drinking water 

regulation

Vulnerability Assessment

An evaluation of drinking water source quality and 

its vulnerability to contamination by pathogens and 

toxic chemicals

Watershed

The land area from which water drains into a 

stream, river, or reservoir

Well

A bored, drilled or driven shaft whose depth is 

greater than the largest surface dimension, a 

dug hole whose depth is greater than the largest 

surface dimension, an improved sinkhole, or a subsurface fluid distribution system

34

www.epa.gov/safewater Safe Drinking Water Hotline: 800-426-4791