Handbook 44 – 2022 3.36. Water Meters

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Table of Contents

Page

Section 3.36. Water Meters.................................................................................................... 3-99

A. Application ...................................................................................................................................................3-99

A.1. General................................................................................................................................................3-99

A.2. Exceptions...........................................................................................................................................3-99

A.3. Additional Code Requirements...........................................................................................................3-99

S. Specifications................................................................................................................................................3-99

S.1. Design of Indicating and Recording Elements and of Recorded Representations. .............................3-99

S.1.1. Primary Elements..................................................................................................................3-99

S.1.2. Graduations.........................................................................................................................3-100

S.1.3. Indicators. ...........................................................................................................................3-100

S.2. Design of Measuring Elements.........................................................................................................3-101

S.2.1. Provision for Sealing...........................................................................................................3-101

S.2.2. Batching Measuring Systems Only.....................................................................................3-102

S.2.3. Multi-Jet Meter Identification.............................................................................................3-102

S.3. Markings...........................................................................................................................................3-103

S.3.1. Location of Marking Information; Utility Type Meters. .....................................................3-103

S.3.2. Meter Size and Directional Flow Marking Information. ....................................................3-103

N. Notes............................................................................................................................................................3-103

N.1. Test Liquid........................................................................................................................................3-103

N.2. Evaporation and Volume Change. ....................................................................................................3-103

N.3. Test Drafts.........................................................................................................................................3-103

N.4. Testing Procedures............................................................................................................................3-103

N.4.1. Normal Tests.......................................................................................................................3-103

N.4.2. Special Tests. ......................................................................................................................3-104

N.4.3. Batching Meter Tests. .........................................................................................................3-105

N.4.4. Repeatability Tests..............................................................................................................3-105

T. Tolerances...................................................................................................................................................3-106

T.1. Tolerance Values. .............................................................................................................................3-106

T.1.1. Repeatability. ......................................................................................................................3-106

UR. User Requirements ....................................................................................................................................3-106

UR.1. Batching Meters Only.......................................................................................................................3-106

UR.1.1. Strainer................................................................................................................................3-106

UR.1.2. Siphon Breaker. ..................................................................................................................3-106

UR.1.3. Provision for Testing...........................................................................................................3-107

UR.2. Accessibility of Customer Indication................................................................................................3-107
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Handbook 44 – 2022 3.36. Water Meters

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This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Section 3.36. Water Meters

A. Application

A.1. General. – This code applies to devices used for the measurement of water; generally applicable to, but not 

limited to, utilities type meters installed in residences or business establishments and meters installed in batching 

systems.

(Amended 2002)

A.2. Exceptions. – This code does not apply to:

(a) water meters mounted on vehicle tanks (for which see Section 3.31. Vehicle-Tank Meters); or

(b) mass flow meters. (Also see Section 3.37. Mass Flow Meters.)

(Added 1994)

A.3. Additional Code Requirements. – In addition to the requirements of this code, Water Meters shall meet the 

requirements of Section 1.10. General Code.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. – A water meter shall be equipped with a primary indicating element and may also be 

equipped with a primary recording element. Such elements shall be visible at the point of measurement or 

be stored in non-volatile and non-resettable memory. The display may be remotely located provided it is 

readily accessible to the customer.

(Amended 2002)

S.1.1.2. Units. – A water meter shall indicate and record, if the device is equipped to record, its deliveries 

in terms of liters, gallons or cubic feet or binary or decimal subdivisions thereof except batch plant meters,

which shall indicate deliveries in terms of liters, gallons or decimal subdivisions of the liter or gallon only.

S.1.1.3. Value of Smallest Unit. – The value of the smallest unit of indicated delivery and recorded 

delivery, if the device is equipped to record, shall not exceed the equivalent of:

(a) 50 L (10 gal or 1 ft3

) on utility type meters, sizes 1 in and smaller; or

(b) 500 L (100 gal or 10 ft3

) on utility-type meters, sizes 11⁄2 in and 2 in; or

(c) 0.2 L (1

/10 gal or 1/100 ft3) on batching meters delivering less than 375 L/min (100 gal/min or 

13 ft 3

/min); or

(d) 5 L (1 gal or 1

/10 ft3) on batching meters delivering 375 L/min (100 gal/min or 13 ft3/min) or more.

(Amended 2009)

S.1.1.4. Advancement of Indicating and Recording Elements. – Primary indicating and recording 

elements shall advance only by the designed operation of the device, as intended by the manufacturer.

(Amended 2021)
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S.1.1.5. Return to Zero. – If the meter is so designed that the primary indicating elements are readily 

returnable to a definite zero indication, means shall be provided to prevent the return of these elements beyond 

their correct zero position.

S.1.1.6. Proving Indicator. – Utility-type meters shall be equipped with a proving indicator. The 

individual graduations on a mechanical (analog) proving indicator shall indicate volumes no larger than 1

/100

of the value of the smallest unit of indicated delivery required in S.1.1.3. Value of Smallest Unit. For 

electronic (digital) proving indications, the smallest unit of volume displayed shall be no larger than 1

/1000 of 

the value of the smallest unit of indicated delivery required in S.1.1.3.

(Added 2009)

S.1.2. Graduations.

S.1.2.1. Length. – Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. – In any series of graduations, the width of a graduation shall in no case be greater than 

the width of the minimum clear interval between graduations, and the width of main graduations shall be not 

more than 50 % greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) in width.

S.1.2.3. Clear Interval Between Graduations. – The clear interval shall not be less than 1.0 mm 

(0.04 in). If the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator; or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. – The index of an indicator shall be symmetrical with respect to the graduations, at 

least throughout that portion of its length associated with the graduations.

S.1.3.2. Length. – The index of an indicator shall reach to the finest graduations with which it is used, the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not 

more than 50 % greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) in width.

S.1.3.3. Width. – The width of the index of an indicator in relation to the series of graduations with which 

it is used shall not be greater than:

(a) the width of the narrowest graduation;* and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of 

the indicator that may be brought into coincidence with the graduation shall be of the same width throughout 

the length of the index that coincides with the graduation.

S.1.3.4. Clearance. – The clearance between the index of an indicator and the graduations shall in no case 

be more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. – Parallax effects shall be reduced to the practicable minimum.
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S.2. Design of Measuring Elements.

S.2.1. Provision for Sealing. – For devices or systems in which the configuration or calibration parameters 

can be changed by use of a removable digital storage device, security shall be provided for those parameters as 

specified in G-S.8.2. Devices and Systems Adjusted Using Removable Digital Storage Devices. For parameters 

adjusted using other means, the following applies.

Adequate provision shall be made for an approved means of security (e.g., data change audit trail) or for physically 

applying a security seal in such a manner that requires the security seal to be broken before an adjustment or 

interchange can be made of:

(a) any measuring or indicating element; 

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of 

deliveries; and

(c) any metrological parameter that will affect the metrological integrity of the device or system.

When applicable, the adjusting mechanism shall be readily accessible for purposes of affixing a security seal.

Audit trails shall use the format set forth in Table S.2.1. Categories of Device and Methods of Sealing.*

*[Nonretroactive as of January 1, 2019]

(Amended 2018 and 2019)
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Table S.2.1.

Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No remote configuration capability. Seal by physical seal or two event counters: one for 

calibration parameters and one for configuration 

parameters.

Category 2: Remote configuration capability, but 

access is controlled by physical hardware.

The device shall clearly indicate that it is in the 

remote configuration mode and record such message 

if capable of printing in this mode or shall not operate 

while in this mode.

The hardware enabling access for remote 

communication must be on-site. The hardware must be 

sealed using a physical seal or an event counter for 

calibration parameters and an event counter for 

configuration parameters. The event counters may be 

located either at the individual measuring device or at 

the system controller; however, an adequate number of 

counters must be provided to monitor the calibration 

and configuration parameters of the individual devices 

at a location. If the counters are located in the system 

controller rather than at the individual device, means 

must be provided to generate a hard copy of the 

information through an on-site device.

Category 3: Remote configuration capability access 

may be unlimited or controlled through a software 

switch (e.g., password).

The device shall clearly indicate that it is in the 

remote configuration mode and record such message 

if capable of printing in this mode or shall not operate 

while in this mode.

An event logger is required in the device; it must 

include an event counter (000 to 999), the parameter 

ID, the date and time of the change, and the new value 

of the parameter. A printed copy of the information 

must be available on demand through the device or 

through another on-site device. The information may 

also be available electronically. The event logger shall 

have a capacity to retain records equal to 10 times the 

number of sealable parameters in the device, but not 

more than 1000 records are required. (Note: Does not 

require 1000 changes to be stored for each parameter.)

[Nonretroactive as of January 1, 2019]

(Table Added 2018)

S.2.2. Batching Measuring Systems Only.

S.2.2.1. Air/Vapor Elimination, Batching Measuring Systems. – Batching measuring systems shall be 

equipped with an effective air/vapor eliminator or other automatic means to prevent the passage of air/vapor 

through the meter. Vent lines from the air/vapor eliminator shall be made of appropriate non-collapsible 

material.

(Amended 2017)

S.2.2.2. Directional Flow Valves. – Valves intended to prevent reversal of flow shall be automatic in 

operation.

S.2.3. Multi-Jet Meter Identification. – Multi-Jet water meters shall be clearly and permanently marked as 

such on the device or identified on the Certificate of Conformance.

(Added 2003)
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S.3. Markings 

S.3.1. Location of Marking Information; Utility Type Meters. – All required markings, including those 

required by G-S.1. Identification, shall be either on the meter body or primary indicator.

[Nonretroactive as of January 1, 2013]

(Added 2012)

S.3.2. Meter Size and Directional Flow Marking Information. – A water meter shall be clearly and indelibly 

marked with the following information:

(a) meter size on the indicator face plate; and

(b) water flow direction.

[Nonretroactive as of January 1, 2022]

(Added 2021)

N. Notes

N.1. Test Liquid. – A meter shall be tested with water.

N.2. Evaporation and Volume Change. – Care shall be exercised to reduce to a minimum, evaporation losses and 

volume changes resulting from changes to temperature of the test liquid.

N.3. Test Drafts. – Test drafts should be equal to at least the amount delivered by the device in two minutes and in 

no case less than the amount delivered by the device in one minute at the actual maximum flow rate developed by the 

installation. The test draft sizes shown in Table N.4.1. Flow Rate and Draft Size for Water Meters Normal Tests, shall 

be followed as closely as possible.

(Amended 2003)

N.4. Testing Procedures.

N.4.1. Normal Tests. – The normal test of a meter shall be made at the maximum discharge rate developed by 

the installation. Meters with maximum gallon per minute ratings higher than the values specified in 

Table N.4.1. Flow Rate and Draft Size for Water Meters Normal Tests may be tested up to the meter rating, with 

meter indications no less than those shown.

(Amended 1990, 2002, and 2003)
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Table N.4.1. 

Flow Rate and Draft Size for Water Meters Normal Tests

Meter Size

(inches)

Rate of Flow

(gal/min)

Maximum Rate

Meter Indication/Test Draft

gal ft3

Less than 5/8 8 50 5

5

/8 15 50 5

3⁄4 25 50 5

1 40 100 10

11⁄2 80 300 40

2 120 500 40

3 250 500 50

4 350 1000 100

6 700 1000 100

(Table Added 2003)

N.4.2. Special Tests. – Special tests to develop the operating characteristics of meters may be made according 

to the rates and quantities shown in Table N.4.2.a. Flow Rate and Draft Size for Water Meters Special Tests and 

Table N.4.2.b. Flow Rate and Draft Size for Utility Type Water Meters Special Tests.

(Amended 2003 and 2010)

Table N.4.2.a.

Flow Rate and Draft Size for Batching Water Meters Special Tests

Meter Size

(inches)

Intermediate Rate Minimum Rate

Rate of Flow

(gal/min)

Meter Indication/Test Draft Rate of Flow

(gal/min)

Meter Indication/Test Draft

gal ft3 gal ft3

Less than or 

equal to 5/8 2 10 1 1⁄4 5 1

3⁄4 3 10 1 1⁄2 5 1

1 4 10 1 3⁄4 5 1

11⁄2 8 50 5 11⁄2 10 1

2 15 50 5 2 10 1

3 20 50 5 4 10 1

4 40 100 10 7 50 5

6 60 100 10 12 50 5

(Table Added 2003) (Table Amended 2010)
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Table N.4.2.b. 

Flow Rate and Draft Size for Utility Type Water Meters Special Tests

Meter Size

(inches)

Intermediate Rate Minimum Rate

Rate of Flow

(gal/min)

Meter Indication/Test Draft Rate of Flow

(gal/min)

Meter Indication/Test Draft

gal ft3 gal ft3

Less than 5/8 2 10 1 1⁄4 5 1

5

/8 2 10 1 1⁄4 5 1

5

/8 × 3⁄4 2 10 1 1⁄4 5 1

3⁄4 3 10 1 1⁄2 5 1

1 4 10 1 3⁄4 5 1

11⁄2 8 100 10 11⁄2 100 10

2 15 100 10 2 100 10

(Table Added 2010)

N.4.3. Batching Meter Tests. – Tests on batching meters should be conducted at the maximum and 

intermediate rates only.

N.4.4. Repeatability Tests. – Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors such as 

temperature, pressure, and flow rate are reduced to the extent that they will not affect the results obtained. When 

conducting the tests, the minimum flow rate shall be at least the minimum rate specified in Table N.4.2.a. Flow 

Rate and Draft Size for Batching Water Meters Special Tests, and the maximum discharge rates shall not exceed 

the maximum discharge rate developed under the conditions of the installation.

(Amended 2019)
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T. Tolerances

T.1. Tolerance Values. – Maintenance and acceptance tolerances shall be as shown in Table T.1. Accuracy Classes 

and Tolerances for Water Meters.

(Amended 2003)

T.1.1. Repeatability. – When multiple tests are conducted at approximately the same flow rate, each test shall 

be within the applicable tolerances and the range of test results shall not exceed the values shown in 

Table T.1.1. Repeatability. Also see N.4.4. Repeatability Tests.

(Added 2002) (Amended 2010)

Table T.1.1.

Repeatability

Batching Meters Utility-Type Meters

Normal Flow Rates 0.6 % 0.6 %

Intermediate Flow Rates 0.6 % 2.0 %

Minimum Flow Rate 1.3 % 4.0 %

(Table Added 2010)

UR. User Requirements

UR.1. Batching Meters Only.

UR.1.1. Strainer. – A filter or strainer shall be provided if it is determined that the water contains excessive 

amounts of foreign material.

UR.1.2. Siphon Breaker. – An automatic siphon breaker or other effective means shall be installed in the 

discharge piping at the highest point of outlet, in no case below the top of the meter, to prevent siphoning of the 

meter and permit rapid drainage of the pipe or hose.

Table T.1. 

Accuracy Classes and Tolerances for Water Meters

Accuracy 

Class Application Acceptance Tolerance

Maintenance 

Tolerance

Tolerance for Special 

Tests Conducted at 

the Minimum Flow 

Rate

1.5

Water, Other 

Than MultiJet Water 

Meters

Overregistration 1.5 % 1.5 % 1.5 %

Underregistration 1.5 % 1.5 % 5.0 %

1.5

Water, MultiJet Water 

Meters

Overregistration 1.5 % 1.5 % 3.0 %

Underregistration 1.5 % 1.5 % 3.0 %

(Table Added 2003)
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UR.1.3. Provision for Testing. – Acceptable provisions for testing shall be incorporated into all meter 

systems. Such provisions shall include a two-way valve, or manifold valving, and a pipe or hose installed in the 

discharge line accessible to the proper positioning of the test measure.

UR.2. Accessibility of Customer Indication. – An unobstructed standing space of at least 76 cm (30 in) wide, 

91 cm (36 in) deep, and 198 cm (78 in) high shall be maintained in front of an indication intended for use by the 

customer to allow for reading the indicator. The customer indication shall be readily observable to a person located 

within the standing space without necessity of a separate tool or device.

(Added 2008)
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