CNPA 49  
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  Technical Specification for Type 
Approval of Water Meters  S/N CNPA 49  
Rev 4 
1. This Technical Specification is developed  pursuant to Paragraph 3 , Article s 25 of the 
Weights and Measures Act.  
2. The date of promulgation, document  number, date of enforcem ent and content of   
amendment are listed as follows:  
 
Rev. Date of  
Promulgation  Document  No. 
(Ching -Piao-Szu-Tsu ) Date of 
Enforcement  Content of Amendment  
1 12.06.2003  No. 09240005480  07.01.2003   
2 08.12. 2005  No. 09440004630  07.01.2006  Revised according  to 
CNS 14866  
3 11.03.2014  No. 10340009830  01.01.2015  Due to the CNS could 
be revised when 
correspondence  
international standards 
or recommendation 
revised,  third edition 
will no longer refer to 
CNS. In addition, there 
are appendixes  added to 
this edition . 
4 04.10.2022  No. 11140007290  07.01.2023  Revised with reference 
to OIML R49: 2013 , 
Added test requirements 
for water meters based 
on electrical or 
electronic principles or 
with additional 
electronic components 
based on mechanical 
principles  
3. The refer ence standards of this technical specification are as follows:  
OIML R49 -1:2013  Water meters for cold potable water and hot water.  
Part 1: Metrological and technical requirements  
OIML R49 -2:2013  Water meters for cold potable water and hot water.  
Part 2: Te st methods  
CNS14866 -1 Measurement of water flow in fully filled closed conduits - Water 
meters for cold and hot water - Part 1: Specification  (Dec 26, 2017) 
CNS 13979  V ortex Flow Meter  (July 9, 2013) 
 
Date of Promulgation  
04.10.2022 Bureau of Standards , Metrology and Inspection, 
Ministry of Economic Affairs  Date of Enforcement  
07.01.2023 
 
 NO GUARANTEE ON THE TRANSLATION  
In case of discrepancies  between the English translation and Chinese text, the Chinese text shall govern.  CNPA 49  
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 1. Scope  
1.1 This technical specification applies to cold potable water meters based on mechanical principle, 
electrical or electronic principle, and mechanical pr inciples incorporating electronic devices, used 
to measure the volume of cold potable water, but not applies to water meters for fire protection.  
1.2 The applicable conditions of the above water meter are as follows : 
1.2.1  The connection method  shall be to  screw  type or flange type, and its  inlet and outlet located 
on both sides of the water meter.  
1.2.2 Nominal diameter range is from 13 mm to 300 mm.  
1.2.3 Permanent flow rate is from 1.6 m3/h to 1000 m3/h. 
1.2.4 The value of the ratio of permanent flow rate  to minimum flow rate is  from  50 to 400 (V ortex 
meter is suitable from  10 to 40). 
1.2.5 The maximum admissible pressure is equal to  or less than  1 MPa.  
1.3 Ancillary devices do not belong to the scope of type approval, but the relevant regulations of the 
Weights and Measures  Act stipulate otherwise.  
2. Definitions of Terms  
2.1 Water meter   
Instrument intended to measure continuously, memorize, and display the volume of water passing 
through the measurement transducer at metering conditions . The indicating d evice and the water 
meter shall be inseparable.  
2.1.1 V olumetric meter  
Device, fitted into a closed conduit, which consists of chambers of known volume and a 
mechanism driven by the flow, whereby these chambers are successively filled with water 
and then e mptied. By counting the number of these volumes passing through the device, the 
indicating device totals the volume flow.  
2.1.2 Velocity meter  
Device, fitted into a closed conduit which consists of a moving element set in motion 
directly by the velocity of  the water flow. The movement of the moving element is 
transmitted by mechanical or other means to the indicating device, which totals the volume 
flow.  
2.1.3 Woltmann meter  
Device consisting of a helical blade that rotates about the axis of flow in the met er. 
2.1.4  Single -jet and multi -jet meters  
Devices consisting of a turbine rotor rotating about the axis perpendicular to the flow of 
water in the meter. The meter is called a single -jet meter if the jet impinges at a single place 
on the rotor’s periphery , and a multi -jet if the jet impinges simultaneously at several points 
around the periphery of the rotor.  
2.1.5  V ortex meters  
Devices comprising a bluff body in the water flow to detect the vortices frequency after the 
bluff body continuously and integratin g an indicator which total the volume flow.  
 
2.2 S ensor  CNPA 49  
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 Element of a meter that is directly affected by a phenomenon, body or substance carryin g a 
quantity to be measured  (For a water meter, the sensor may be a disc, piston, wheel or turbine 
element, the e lectrodes on an electromagnetic meter, or another element ). 
The calculator may be capable of communicating both ways with ancillary devices.  
2.4 Indicating device  
Device displaying the volume flowing.  
2.5 Ancillar y device  
Device intended to perform a specific function, directly involved in elaborating, transmitting or 
displaying measured values, but is not a device necessary for a water meter.  
The main  ancillary devices are : 
─ repeating indicating device;  
─ memory device;  
─ remote r eading device  (which may be incorporated permanently or added temporarily).  
2.6 Metrological characteristics  
2.6.1 Actu al volume, Va  
Total volume of water passing through the meter, disregarding t he time taken. The actual 
volume is calculated from a reference volume as determined by a suitable measurement 
standard, taking into account differences in metering conditions, as appropriate . 
2.6.2 Indicated volume, Vi 
V olume of water indicated by the met er, corresponding to the actual volume.  
2.6.3 Primary indication  
Indication which is subject to legal metrological control.  
2.6.4 Error  
Measured quantity value minus a reference quantity value. The indicated volume is 
considered as the measured quantity va lue and the actual volume as the reference quantity 
value. The difference between indicated volume and actual volume is referred to as: error.  
In this Technical Specificat ion, the error  (of indication) is expressed as a percentage of the  
actual volume, and  is equal to  
𝑉i−𝑉a
𝑉ax100%  
 
2.6.5 Maximum permissible error, MPE  
Extreme value of measurement error, with respect to a known reference quantity value, 
permitted by specifications or regulations for a given meter.  
2.6.6 Durability  2.3 Calculator   
Part of the meter that transforms the output signals from the measurement transducer(s) and, 
possibly, from associated  measuring instruments and, if appropriate, stores the results  in memory 
until they are used . 
The gearing is considered to be the calculator in a mechanical meter.  CNPA 49  
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 Ability of a meter  to maintain its perf ormance characteristics over a period of use . 
2.7 Operating conditions  
2.7.1  Flow rate , Q 
Q = dV/dt where V is actual volume and t is time taken for this volume to pass through the 
meter . The flow rate is expressed in m3/h. 
2.7.2  Permanent flow rate , Q3 
Highest flow rate within the rated operating conditions at which the meter is to operate 
within the maximum permissible errors . 
2.7.3 Overload  flow rate, Q4 
Highest flow rate at which the meter is to operate for a short period of time within the 
maximum perm issible errors, while maintaining its metrological performance when it is 
subsequently operating within  the rated operating conditions . 
2.7.4  Transitional flow rate , Q2 
Flow rate between the permanent flow rate and the minimum flow rate that divides the fl ow 
rate range into two zones, the upper flow rate zone  (Q2 ≤ Q ≤ Q4) and the lower flow rate 
zone  (Q1 ≤ Q < Q2), each characterized by its own maximum permissible errors.  
2.7.5 Minimum flow rate , Q1 
Lowest flow rate at which the meter is to operate within the maximum permissible errors . 
2.7.6 First element of an  indicating device  
Element which , in an indicating device comprising several elements, carries the graduated 
scale with the verification scale interval.  
2.7.7 Verification scale interval  
Lowest value scale  division of the first element of an indicating devic e. 
2.7.8 Maximum admissible pressure , MAP  
 Maximum internal  pressure that a meter can withstand permanently, within its rated 
operating conditions, without deterioration of its metrological performance.  
2.7.9 Working pressure , pw 
Average water pressure  (gauge) in the pipe measured upstream and downstream of the 
meter . 
2.7.10 Pressure loss , △P 
Pressure loss cased by the presence of a water meter in the pipeline at a given flowrate.  
2.7.11 Nominal diameter , DN 
Alphanumeric designation of size for components o f a pipework system, which is used for 
reference purposes.   
The nominal diameter is a dimensionless whole number which is indirectly related to the 
physical size, in millimetres, of the bore or outside diameter of the end connections.  
2.7.12  Nominal pressu re, PN 
Numerical designation  which is a rounded number for reference purposes. All equipment of 
the same nominal size  (DN) and designated by the same PN number  shall have compatible 
mating dimensions.  
2.7.13 Intrinsic error  CNPA 49  
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 Error of a meter determined unde r reference condition s. 
2.7.14 Initial intrinsic error  
Intrinsic error of a meter as determined prior to performance tests and durability 
evaluations . 
2.7.15 Fault  
Difference between the error  (of indication) and the intrinsic error of a meter . 
2.7.16 Significant fault  
Fault greater than a value equal to one half of the MPE . 
3. Metrological  requirements   
3.1 Values of Q1, Q2, Q3, and Q4 
3.1.1 The flow rate characteristics of a water meter shall be defined by the values of Q1, Q2, Q3, 
and Q4. 
1.6 2.5 4 6.3 10 
16 25 40 63 100 
160 250 400 630 1000  
3.1.4 The ratio Q2/Q1 shall be 1.6.  
3.1.5 The ratio Q4/Q3 shall be 1.25.  
3.2 Accuracy  class and maximum permissible error  
The water meter shall be designed and manufactured s uch that its errors  (of indication) do not 
exceed the maximum permissible errors  (MPEs) as defined in Table 1 under rated operating 
conditions. The accuracy class is classified as class 1 or class 2. The manufacturer shall specify the 
accuracy class.  
Table  1 Accuracy grades and tolerances  
flow rate  MPE  
class 1  class 2  
Q1 ≤ Q  ＜  Q2 ±3 ％ ±5 ％ 
Q2 ≤ Q ≤ Q4 ±1 ％ ±2 ％ 3.1.2 The v alue of Q3, expressed in m3/h, shall be chosen from the following list : 
3.1.3The value of the ratio Q3/Q1 shall be chosen from the following  list: (Among them, 
values ≤ 40 are only applicable to the vortex flow meter ) 
10 12.5 16 20 25 31.5 40 50 63 80 
100 125 160 200 250 315 400    CNPA 49  
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 (d) it shall withstand accidental reverse flow at a flow rate up to Q3 without deterioration or 
change in its metrological properties for forward flow.  
3.4 The water  meter totalization shall not change in the absence ei ther of flow or of water.  
(b) twice the maximum admissible pressure applie d for 1 min.  
3.6 F low profile sensitivity  
The flow field sensitivity of the water meter is tested with a flow disturber  (Appendix A), and its 
classification is shown in Table 2 and Table 3. A meter manufacturer shall specify the flow profile 
sensitivity cl ass in accordance with Tables 2 and 3.  
Table 2 Sensitivity to irregularity in the upstream velocity field classes (U)  
Class  Required straight length ×DN Straightener needed  
U0 0 No 
U3 3 No 
U5 5 No 
U10 10 No 
U15 15 No 
U0S 0 yes 
U3S 3 yes 
U5S 5 yes 
U10S  10 yes 
 
 
 
 
 
 3.3 Reverse  flow 
The manufacturer shall specify whether or not a water meter is designed to measure reverse flow.  
If a meter is designed to mea sure reverse flow, the design of its water meter shall adopt one of th e 
following two methods : 
(a) the volume passed during reverse flow shall either be subtracted from the indicated volume  
or 
(b) provide a indicating device for reverse flow. In this case, the Q3 of the indicating device for 
forward flow is different from that of the indicating device for reverse flow.  
If a meter is not designed to measure reverse flow, the design of its water meter shall adopt o ne of 
the following two methods : 
(c) there is a design to  force the occurrence of reverse flow  or 
3.5 Static pressure : A water meter shall be capable of withstanding the following  test pressures without 
leakage or damage . 
(a) 1.6 times the maximum admissible pressure applied for 15 min;  CNPA 49  
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 Table 3 Sensitivity to irregularity in the downstream velocity fields classes (D)  
Class  Required straight length ×DN Straightener needed  
D0 0 No 
D3 3 No 
D5 5 No 
D0S 0 yes 
D3S 3 yes 
Note: Sensitivity level symbol  
UXS: U means upstre am, D means downstream, X means pipe diameter multiple, and S means rectifier 
required  
4. Water meters  equipped with electronic devices  
4.1 A water meter equipped with electronic devices shall be designed and manufactured in such a way 
that exceed the MPE of the upper zone or significant faults do not occur when it is exposed to the 
disturbances specified in Section 8 . 
4.2 The power source c an be external power supply, non -replaceable battery and replaceable battery.  
4.3 External power supply  
4.4 The manufacturer shall ensure that the expected lifetime of the non -replaceable battery is such that 
a meter functi ons correctly for at least one year longer than the operatio nal lifetime of the meter.  A 
low battery or exhausted battery indicator or a meter replacement date shall be indicated on the 
meter.  
If the register display gives an indication of “low battery”, there shall be at least 180 days of useful 
life for the regi ster display from the time “low battery” indication is displayed to end of life.  Example: U5S upstream straight pipe 5 times, need  Straightener , 
D3 downstream straight pipe 3 times, no  Straightener . 
4.3.1 A water meter  with electronic devices shall be designed such that in the event of an external 
power supply failure  (AC or DC), the meter indicatio n of volume just before failure is not 
lost, and remains accessible for a minimum of one year.   
The corresponding memorization shall occur at least either once per day or for every volume 
equivalent to 10 min of flow at Q3.  
Any other properties or paramet ers of a meter shall not be affected by an interruption of the 
power supply.  
4.5 Where  the electrical power supply is a replaceable battery, the manufacturer shall give precise rules 
for the replacement of the battery .  
A low battery or exhausted batte ry indicator or a battery replacement date shall be indicated on the 
meter. If the register  display gives an indication of “low battery”, there shall be at least 180 days 
of useful life for the register display from the time “low battery” indication is dis played to end of 
life.  
The prop erties and parameters of a meter shall not be affected by the interruption of the electrical 
supply when the battery is replaced .  
When rep lacing the battery, the seal shall be destroyed . CNPA 49  
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 5. Technical requirements  
5.1 All pa rts of a water meter in contact with the water flowing through it shall be manufactured from 
materials which are  conventionally known to be non -toxic, non -contaminating, and biologically 
inert. The materials shall be determined by the water utility agencie s and identified the 
requirements in the procurement specifications.  
5.2 A water meter shall be manufactured from materials of adequate strength and durability for the 
purpose for which it is to be used.  
5.3 A water meter shall be manufactured from materia ls which shall not be adversely affected by the 
water temperature variations, within the working temperature range . 
5.4 The complete water meter shall be manufactured from materials which are resistant to internal and 
external corrosion or which are protec ted by a suitable surface treatment.  
5.5 A water meter indicating device shall be protected by a transparent window. A cover of a suitable 
type may also be provided as additional protection.  
5.6 Structure  
5.6.1 The me ter size and overall dimensions of volu metric and velocity water meters shall be in 
accordance with Appendix B. 
5.6.2 The me ter size and overall dimensions of vortex water meters shall be in accordance with 
Appendix C. 
5.8 V olumetric and velocity multi -jet meters shall be equipped with appropriate strainers at the inlet. 
5.9 After verified and se aled, the measurement errors or zero -setting of water meters shall not be able 
to be adjusted by external methods or devices. If the meter is provided with a zero -setting device 
for special purposes, the zeroing position shall be zeroed upon operation, but  the totaling device 
shall not be zeroed.  
5.10 The shell of a water meter should not be coated with wax, soluble glass or any other leak proof 
material; the shell of a water meter should be free of sags, crests, scratches or any traces of repair. 
A positio n shall be reserved for the lead seal.  
However, the interior and exterior of the shell of a big water meter with a nominal size of not less 
than 50 mm may be coated with rustproof paint or powder coating.  
5.11 Where there is a risk of condensation forming  on the underside of the window of a water meter 
indicating device, the water meter shall incorporate devices for prevention or elimination of 
condensation.  
5.12 A water meter shall be of such design, composition, and construction that it does not facilita te the 
perpetration of fraud.  
5.13 Marks and inscriptions  
5.13.1  The water meter size should be marked on the lid exterior center and the side of water 
meter.  
5.13.2 The direction of flow  (→) shall be marked on both sides of the water meter.  
5.13.3  Name or  trademark of the manufacturer shall be marked on one side of water meter exterior 5.7 The transparent lid of a water meter shall be transparent and clear, and  must not be loosened when 
pressed by hand.   
The top lid of the water meter shall be opened equal to or more than 120 degrees.  CNPA 49  
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 or on the indicating device.  
5.13.4  The serial number should be marked on the edge of meter exterior.  
5.13.5  The indication range  (maximum capacity of accumulation) and numb ers of meter shall be 
marked on the indicating device.  
5.13.6 The model number shall be marked on the indicating device clearly.  
5.13.7  A position for marking the type approval number shall be reserved in an obvious position 
on the indicating device.  
5.13. 8 The validity period of verification shall be marked on the edge of the upper shell.  
5.13.9 The water meter shall be installed in the horizontal posit ion. The installation direction (H) 
shall be marked on both sides of water meter or on the indicating devi ce of water meter 
The vortex water meters are excluded . 
5.13.10 A water meter shall be clearly and indelibly marked with the information of numerical 
value of Q3, the ratio Q3/Q1, accuracy class, the pressure loss class and nominal pressure . If 
the meter m easures reverse flow and the values of Q3 and the ratios Q3/Q1 are different in 
the two directions, both values of Q3 and Q3/Q1 shall be inscribed . 
5.13.11 The flow profile sensitivity class should be marked in a prominent place . 
6. Indicating  device  
6.2 Unit of measurement, symbol and its placement  
The volume of water measured  shall be expressed i n cubic metres. The unit symbol  (m3) shall 
appear on the dial or immediately adjacent to the numbered display.  
6.3 Indicating range  
The indicating device shall be able to record the indicated volume in cubic metres given in Table 4 
without passing through zero.  
 
Table 4 Indicating range of a water meter  
Q3 
m3/h Indicating range 
(minimum values)  
 m3 
Q3 ≤ 6.3 9 999  
6.3 < Q3 ≤ 63 99 999  
63 < Q3 ≤ 630 999 999  
630 < Q3 ≤ 1 000  9 999 999  6.1 Functi ons 
The indicating device of a water meter shall provide an easily read, reliable, and unambiguous 
visual indication of the indicated volume.  The indicating device shall display the volume either 
continuously, periodically or on demand.  The indicating  device shall include visual means for 
testing and verification.  The indic ating device may include additional elements for testing by other 
methods . CNPA 49  
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 (b) Electronic digital indicator  
The color black should be used to indicate the cubic metre and its multiples.  
6.5 Types of indicating device  
Any of the following types  shall be used.  
Rotational movement of the pointers or circular scales shall be clockwise. Linear movement 
of pointers or scales  shall be left to right. Movemen t of numbered roller indicators  (drums) 
shall be upwards.  
6.5.2 Type 2 – Digital  device  
The indicated volume is given by a line of adjacent digits appearing in one or more apertures. 
The advance of a given digit shall be com pleted while the digit of the next immediately lower 
decade changes from 9 to 0. The apparent height of the digits shall be at least 4 mm.  
Each step of the sequence shall last at least 1 s.  
6.5.3 Type 3 – Combination of analogue and digital devices  
The indicated volume is given by a combination of type 1 and type 2 devices and the 6.4 Color coding for indicating devices  
(a) Non-electronic digital indicator  
The color black should be used to indicate the cubic metre and its multiples.  The color red 
should be used to indicate sub -multiples of a cubic metre.  These colors shall be applied to 
either pointers, indexes, numbers, wheels, discs, dials or to the aperture  frames . 
6.5.1  Type 1 – Analogue device  
The indicated  volume is indicate d by continuous movement of  
(a) one or more pointers moving relative to graduated scales, or  
(b) one or more circular scales or drums each passing an index.  
The value expressed in cubic metres for each scale division shall be of the form 10n, where n is 
a positive or negative whole number or zero, thereby establishing a system of consecutive 
decades. Each scale shall either be : 
─ graduated in values expressed in cubic metres  
─ or accompa nied by a multiplication factor  (×0.001; ×0.01; ×0.1; ×1; ×10; ×100; ×1 000, etc.)  
(a) For non -electronic devices: Movemen t of numbered roller indicators  (drums) shall be 
upwards. If the lowest value decade has a continuous movement, the aperture shall be 
large enough to permit a digit to be read unambiguously.  
(b) For electronic devices: Either permanent or non -permanent displays are permitted. For 
non-permanent displays, the volume shall be able to b e displayed at any time for at least 
10 s. The meter shall provide visual checking of the entire display which shall have the 
following sequence:  
─ for seven segment t ype displaying all the elements  (e.g. an “eights” test);  
─ for seven segment  type blanking all the elements  (a “blanks” test);  
─ for graphical displays an equivalent test to demonstrate that display faults cannot result in 
any digit be ing misinterpreted.  CNPA 49  
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 respective requirements of each shall appl y. 
6.5.4 Verification scale interval  
6.5.4.1 Every indicating device shall provide means for visual, non -ambiguous verification 
testing. The visual verification display may have either a continuous or a 
discontinuous movement.  
6.5.4.2 Verific ation Scale Interval  
The indicator element  with the smallest decimal number, and its smallest decimal 
scale value is called the verification scale interval. In addition to the visual 
verification display, an indicating device may include provisions for rapid testing by 
the incl usion of complementary elements  (e.g. star wheels or discs), providing signals 
through externally attached sensors and convert the recorded data into numerical data.  
6.5.4.3 The value of the verification scale interval expressed in cubic metres sha ll be of the 
form: 1 × 10n, 2 × 10n or 5 × 10n, where n is a positive or negative whole number, or 
zero. For analogue and digital indicating devices with continuous movement of the 
first element, the verification scale may be formed from the division into 2, 5 or 10 
equal parts of the interval between two consecutive digits of the first element. 
Numbering shall not be applied to these divisions.  
(b) On indicating devices with non -continuous movement of the first element, the 
verification scale interval is the interval between two consecutive digits or incremental 
movemen ts of the first element.  
6.5.5 The minimum  verification scale of the indicating device shall meet the requirements in Table 
5. 
Table 5 Minimum subdivisions value  
 
 
 
 
(b) If the minimum verificat ion scale is discontinuous, an allowance shall be made for a 
maximum error in each reading of not more than one digit of the verification scale.  
7. Performance test 
7.1 The evaluation tests shall be made on the minimum number of samples of each type shown in Table 
6 as a function of the water meter designation Q3 of the type presented. The authority responsible 
for type approval may request  further specimens.  
For type approval of a water meter with electronic devices, five samples shall be supplied for the 6.5.4.4 Form of the verification scale  
(a) On indicating devices with continuous movement of the first element, t he apparent 
scale spacing shall be not less than 1 mm and not more than 5 mm.  
Accuracy  continuous  discontinuous  
Class 1  1.5Q1  0.25％ 1.5Q1  0.125％ 
Class 2  1.5Q1  0.5％ 1.5Q1  0.25％ 
(a) If the minimum verification scale is continuous, an allowance shall be made for a 
maximum error in each reading of not more than half the verification scale interval.  CNPA 49  
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 tests specified in Section 8, which may be different samples from those supplied for other testing, 
with at least one meter being subjected to all the appropriate tests. The same meter shall be 
subjected to all testing . 
Table 6 Minimum number of water mete rs to be tested  
Q3   
m3/h Minimum number of meters to be tested for all meter types, 
excluding the tests required for meters with electronic devices  
Q3  ≤ 160  3 
160 < Q3 ≤ 1,000  2 
7.2 Meters are tested either individually or in groups. In the latter case, the straight lengths between the 
meters shall be enough. The presence of any meter in the test rig shall not contribute significantly 
to the test error  of any other meter. During the tests, the gauge pressure at the outlet of each water 
meter shall be at least 0.03 M Pa (0.3 bar).  
7.3 Static pressure  
A water meter shall be capable of withstanding the following test pressures without leakage or 
damage:  
7.3.1 1.6 Times the maximum admissible pressure applied for 15 min and twice the maximum 
admissible pressure  applied for 1 min.  
7.3.2  Acceptance criteria  
There shall be no leakage from the meter or physical damage. For a water meter with a dry 
indicating devi ce, water should not be immersed in the upper gear chamber and the indicating 
device.  
7.4 Errors  (of indication)  
7.4.1 Test method  
It can be the volume method, the weighing method or the standard table method. The 
expanded uncertainty  of the equipment used  shall not exceed one -fifth of the  MPE , and the 
coverage factor of the estimated uncertainty is k=2. 
7.4.2 Flow rate  
Determine the intrinsic errors  (of indication) of a water meter  (in the measurement of the 
actual volume), for at least the following flow rates, the error at each flow rate being 
measured three times for  (a), (b) and  (e) and twice for the other flow rate ranges.  The relative 
errors  (of indication) observed for each of the flow rates shall not exceed the maximum 
permissible errors given in Ta ble 1 in section 3.2 . 
(a) Q1 to 1.1 Q1; 
(b) Q2 to 1.1 Q2; 
(c) 0.33 × ( Q2 + Q3) to 0.37 × ( Q2 + Q3); 
(d) 0.67 × ( Q2 + Q3) to 0.74 × ( Q2 + Q3); 
(e) 0.9 Q3 to Q3; 
(f) 0.95 Q4 to Q4; 
This flow rate variation condition is acceptable if the relative pressu re var iation  (in flow to CNPA 49  
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 free air) or the relative variation of pressure loss  (in closed circuits) does not exceed:  
±5 % from Q1 to Q2 (exclusive);  
±10 % from Q2 (inclusive) to Q4. 
The relative variation in the flow rate during each test (not including starting and stopping) 
shall not exceed:  
±2.5 % from Q1 to Q2 (exclusive);  
±5.0 % from Q2 (inclusive) to Q4. 
7.4.3  Orientation  of water meter(s)  
Mount the connecting  pipework with the flow axis in the horizontal plane during the test  
(indicating device positioned o n top).  
7.4.4 Where the initial error curve is close to the maximum permissible error at a point other than 
at Q1, Q2 or Q3, if this error is shown to be typical of the meter type, the body responsible for 
type approval may choose to define an additional f low rate for verification to be included in 
the type approval certificate.  
(c) The standard deviation for section 7.4. 2(a), (b) and (e) shall not exceed one -third of the 
maximum permissible errors . 
7.5 Water pressu re test  
Measure the error  (of indication) of at least one meter at a flow rate of Q2 with the inlet pr essure 
held firstly at 0.03 MPa  (0.3 b ar)(the test pressure error range is 0  % ~ 5 %) and then at the 
maximum admissible pressure  (MAP) ( the maximum allow able pressure does not exceed 1 MPa, 
and the test pressure error range is -10 % ~ 0 %). The relative errors  (of indication) shall not 
exceed the maximum permissible errors given in Table 1 in section 3.2 . 
7.6 Reverse flow test  7.4.5  Acceptance criteria  
(a) The relative errors (of indication) observed for each of the flow rates shall not exceed the 
maximum permissible errors given in Table 1. If the error observed on one or more meters 
is greater than the maximum permissible error at one flow rate only, then if only two 
results have been taken at that flow rate, the test at that flow rate shall be repeated; the test 
shall be declared satisfactory if two out  of the three results at that flow rate lie within the 
maximum permissible error and the arithmetic mean of the results for the three tests at 
that flow rate lies within the maximum permissible error.  
(b) If all the relative errors (of indication) of a wat er meter have the same sign, at least one of 
the errors shall not exceed one -half of the maximum permissible error.  
7.6.1 Meters  designed to meas ure reverse flow  
Measure the error  (of indication) of at least one meter at each of the following reverse flow 
rate ranges:  
(a) Q1 to 1.1 Q1; 
(b) Q2 to 1.1  Q2; 
(c) 0.9 Q3 to Q3. CNPA 49  
 Page 14 of 55 
 The relative errors  (of indication) shall not exceed the maximum permissible e rrors given in 
Table 1 in section 3.2 . In addition, the following tests shall be carried out with the application 
of reverse flow: pressure loss test and durability test.  
Error  must meet the requirements in Table 1 in section 3.2 . 
Error  must meet the requirements in Table 1 in section 3.2 . 
7.7 Pressure loss test  
7.7.1 The pressure  loss class is selected by the manufacturer  choice  from the values in Table 7. 
And t he water meter is tested for pressure loss as shown in Figure 1. When the pressure loss 
test value exceeds the maximum value listed in the classification, it is judged to be 
unqualified.  
Table 7 Pressure loss classes  
Class  Maximum pressure loss  
MPa  bar 
△p63 0.063  0.63 
△p40 0.040  0.40 
△p25 0.025  0.25 
△p16 0.016  0.16 
△p10 0.010  0.10 
7.7.2 To determine the maximum pressure loss through a water meter at any flow rate between Q1 
and Q3. 7.6.2 Meters not designed to measure reverse flow  
Subject the meter to a reverse flow  of 0.9 Q3 for 1 min.  Measure the error  (of indication) of at 
least one meter at the following forward flow rate ranges : 
(a) Q1 to 1.1 Q1; 
(b) Q2 to 1.1 Q2; 
(c) 0.9 Q3 to Q3. 
7.6.3 Meters which pr event reverse flow  
Meters which prevent reverse flow should be subjected to the maximum admissible pressure 
in the reverse flow direction for 1 min. Check that there is no significant leak past the valve.  
Measure the error  (of indication) of at least one m eter in the following forward flow rate 
ranges:  
(a) Q1 to 1.1  Q1; 
(b) Q2 to 1.1 Q2; 
(c) 0.9 Q3 to Q3. CNPA 49  
 Page 15 of 55 
 Slits should be perpendicular to the pipe axis and should have dimensions as follows:  (refer 
to Figure 3)  i=0.08D，and 2 mm  ≤ i ≤ 4 mm，k＞2i. 
7.7.4 A single pressure tapping may be provided and would be suitable for most tests. There should 
be at least four such pressure tapping holes, equally spaced in one plane around the pipe 
circumference  (see Figure 2, Figure 3 an d Figure 4). These would be interconnected by 
means of tee -shaped connectors to form an annul ar and to give a true mean static pressure at 
the pipe cross -section. Other methods such as ring or balance chamber may also be used.  
7.7.5 The upstream and downst ream pipes should be round and of smooth bore to minimize 
pressure loss in the pipe. The minimum  dimensions for installing the tappings are shown in 
Figure 1. The upstream tapping should be positioned a distance of at least 10 D, where D is 
the internal pi pe diameter, downstream of the entrance to avoid errors being introduced by the 
entry connection and be positioned at least 5 D upstream of the meter . The downstream 
tapping should be at least 10 D downstream of the meter to allow pressure to recover 
follo wing any restrictions within the meter and at least 5 D upstream of the end of the test 
section . 
 
Key 
1      differential manometer                            L1 ≥ 10 D 
2      water meter  (plus manifold, for concentric meters )      L2 ≥ 5 D 
P1, P2  planes of the pressure tappings                      L3 ≥ 10 D 
a      Flow direction                                    L4 ≥ 5 D 
b      Measuring section                      where D is the internal diameter of the pipe -work  
Figure 1 Pressure loss test: layout of measuring section  
 7.7.3 The pressure tapping hole can be a round hole or an annular gr oove. Holes drilled through 
the pipe wall should be perpendicular to the pipe axis.  (refer to Figures 2 and 4). The pressure 
tapping hole  diameter, d, is equal to 0.08D and is between 2 mm and 4 mm . If the pipe 
diameter is less than or equal to 25 mm, the tappings should be as close to 2 mm in diameter 
as possible. The diameter of the holes should remain constant for a distance of not less than 
twice the tapping diameter before breaking into the pipe.  The holes drilled through the pipe 
wall should be free f rom burrs at the edges where they break through into the inlet and outlet 
pipe bores.  The edges should be sharp: they should have neither a radius nor a chamfer.  
2
2 CNPA 49  
 Page 16 of 55 
  
 
 
Figure 2 Example of drilled hole type of pressure tapping with ring chamber, suitable for 
small/medium diameter test sections  
 
 
 
 
 
Figure 3 Example of slit type of pressure tapping with ring chamber, suitable for small/medium diameter 
test sections  
CNPA 49  
 Page 17 of 55 
 
 
 
 
Figure 4 Example of drilled hole type of pressure tapping with connections between tappings to 
give mean static pressure, suitable for med ium or large diameter test sections . 
7.7.6 The meter should be installed in the measuring section in the test facility. Flow is established 
and all air purged from the test section. Adequate back pressure should be ensured at the 
downstream pressure tappin g at the maximum flow rate Q3. As a minimum, a static pressure 
downstream of the meter under test of 100 kPa  (1 bar) is recommended to avoid cavitation or 
air release. While monitoring the differential pressure, the flow should be varied between Q1 
and Q3. The flow rate showing the largest pressure loss, Qt, should be noted along with the 
measured pressure loss and fluid temperature. Normally Qt will be found to be equal to Q3. 
7.7.7 The test section  can be rearranged as shown in Figure 5. Calculate the pre ssure loss, Δpt, of 
the water meter.  
Δpt = Δpm+p– Δpp 
where:  
Δpm+p is the measured pressure loss at Qt with the meter in place;  Key 
A  cross -section through pipe and pressure tappings  
B  detail of pressure tapping and boss  
y  vertical axis  
x  horizontal axis  
1  tee 
2  flexible hose or copper pipe  
3  pressure tapping (see B)  
4  isolating cock  
a  To manometer  CNPA 49  
 Page 18 of 55 
 Δpp is the pressure loss measured without the meter at Qt. 
If the measured flow rate either during the test or during the deter mination of the pipe pressure 
loss is not equal to the selected test flow rate, the measured pressure loss can be corrected to 
that expected at Qt by reference to the square law formula as follows:  
△pQt=
△pQmeas  
where:  
 is the calculated pressure loss at Qt. 
Qmeas is the flow rate when measures the pressure loss . 
 is the measured pressure loss at a flow rate Qmeas. 
 
(a) Pipe pressure loss  
 
(b) (Pipe and water meter) pressure loss  CNPA 49  
 Page 19 of 55 
 b  Measuring section  
Figure 5 Pressure loss test  
7.8 Flow disturbance  tests 
Except for the following requirements, all water meters must be tested at a flow rate between 0.9 Q3 
and Q3 in the following order : 
(a) V olumetric water meters (ie, those including measuring chambers with movable walls) are 
exempt from testing.  
(b) For meters where the manufacturer has specified installation length of straight pipe of at least 
15 times DN upstream and 5 times DN downstream of the meter, where DN is the nominal 
diameter, no external flow str aighteners are allowed.  
(c) When a minimum straight pipe length of 5 times DN downstream of the meter is specified by 
the manufacturer, only tests 1, 3 and 5 shall be performed.  
(d) Where meter installations with external flow straighteners are to be used,  the manufacturer 
shall specify the straightener model, its technical characteristics and its position in the 
installation relative to the water meter.  
(e) Please refer to Appendix A for the types of straightener . 
(f) Acceptance standard: refer to Table 1 . 
 
 
Test 1: without a straightener  Key 
1  differe ntial manometer  
2  water meter in downstream position (or temporary pipe)  
3  water meter  
P1, P2  planes of the pressure tappings  
Δp1  pressure loss of up - and downstream pipe lengths  
△p1=(△pL2+△pL3) 
Δp2  pressure loss of up - and downstream pipe lengths and water meter  
△p2=(△pL2+△pL3+△pmeter) 
△p2－△p1=(△pL2+△pL3+△pmeter)－(△pL2+△pL3) =△pmeter  
a  Flow direction  CNPA 49  
 Page 20 of 55 
 
 
Test 1A: with a straightener  
 
Test 2: without a straightener  
 
Test 2A: with a straightener  
 
Test 3: without a straightener  
 CNPA 49  
 Page 21 of 55 
 Test 3A: with a straightener  
 
Test 4: without a straightener  
 
Test 4A: with a straightene r 
 
Test 5: without a straightener  
 
Test 5A: with a straightener  CNPA 49  
 Page 22 of 55 
 
 
Test 6: without a straightener  
 
 
Test 6A: with a straightener  
Figure 6 Installation requirements for flow disturbance tests  
 
7.9 Durability tests  
7.9.1 Discontinuous flow test  
This test is applied only to meters with Q3 ≤ 16 m3/h. 
7.9.1.1  The discontinuous flow test consists of subjecting the meter to the specified number 
of starting and stopping flow rate cycles of short  duration . A complete cycle 
comprises the following four phases: a period from zero to the test flow rate, a period 
at constant test flow rate, a period from the test flow rate to zero, and a period at zero 
flow rate. For the convenience of laboratories, the test can be divided up into periods 
of at least 6 h.  Key 
1  type 1 disturber — swirl generator sinistrorsal  
2  Meter   
3  straight length   
4  straightener  
5  type 2 disturber — swirl generator dextrorsal  
6  type 3 disturber — velocity profile flow  disturber . CNPA 49  
 Page 23 of 55 
 (f) indicated volumes of the  meter(s) under test.  
7.9.1.3 Following the discontinuous durability test, measure the final errors (of indication) of 
the meters as specified  in Section 7.4.2 and then perform the continuous flow test. The 
acceptance criteria after discontinuous durabilit y test shall meet the requirements in 
Table 8.  7.9.1.2 The relative  variation of the flow values shall not exce ed ±10% outside the opening, 
closing, and stoppage periods.  
The tolerance on the test timing on the specified duration of each phase of the flow 
cycle shall not exceed ±10%. The tolerance on the test timing on the total test duration 
shall not exceed ±5%. 
The total theoretical volume duration of the test with a tolerance of ±5%. 
During the test, the following readings from the test rig shall be recorded at least once 
every 24 h period, or once for every shorter period if the test is so divided:  
(a) line pre ssure upstream of the meter(s) under test;  
(b) line pressure downstream of the meter(s) under test;  
(c) line temperature upstream of the meter(s) under test;  
(d) flow rate through the meter(s) under test;  
(e) number of cycles;  CNPA 49  
 Page 24 of 55 
 Table 8 Acceptance criteria  after discontinuous durability test  
Flow rate  MPE  
Class 1  Class  2 
Q1 ≤ Q＜Q2 ±4 ％ ±6 ％ 
Q2 ≤ Q ≤ Q4 ±1.5 ％ ±2.5 ％ 
7.9.1.4 Comparing the final errors (of indication) of the meter s as specified in Section 7.4.2, 
the variation in the error curve shall meet the requirements in Table 9. For the purpose 
of determining these requirements, the mean values of the errors (of indication) at each 
flow rate shall apply.  
 
Table 9 The variation  in the error curve after the discontinuous durability test  
Flow rate  Maximum erro r limit 
of variation curves  
Class 1  Class  2 
Q1 ≤ Q＜Q2 ±2 ％ ±3 ％ 
Q2 ≤ Q ≤ Q4 ±1 ％ ±1.5 ％ 
7.9.2  Continuous  flow test  
7.9.2.1  The test consists of subjecting the meter to constant flow rate of Q3 or Q4 for a 
specified duration. For the convenience  of laboratories, the test can be divided up into 
periods  of at least 6 h.  
7.9.2.2  The relative variation of the flow rate values during e ach test shall not exceed ±10 %  
(except when starting and stopping). The water meter(s) on test may be used to check 
the flow rate.  
During the test, the following readings f rom the test rig shall be recorded at least once 
every 24 h period, or once for every shorter period if the test is so divided:  
(a) water pressure upstream of the meter(s) under test;  
(b) water pressure downstream of the meter(s) under test;  
(c) water temp erature upstream of the meter(s) under test;  
(d) flow rate through the meter(s) under test;  
(e) indicated volume of the meter(s) under test.  
7.9.2.3 After the continuous durability  test(s), measure the errors  (of indication) of the 
meter(s) as specified in  Section 7.4.2. Calculate the relative error  (of indication) for 
each flow rate. Acceptance criteria after continuous flow test  shall meet the 
requirements in Table 10.  CNPA 49  
 Page 25 of 55 
 Table 10 Acceptance criteria after continuous durability  test 
Flow rate  MPE  
Class 1  Class 2  
Q1 ≤ Q＜Q2 ± 4 ％ ± 6 ％ 
Q2 ≤ Q ≤ Q4 ± 1.5 ％ ± 2.5 ％ 
7.9.2.4  Compare the error  (of indication) obtained of the following with the error  (of 
indicati on) obtained in Section 7.9.2.3  
(a) When Q3 ≤16 m3/h, compare the error (of indication) obtained in Section 7.9.1.3;  
(b) When Q3 > 16 m3/h, compare the error (of indication) obtained in Section 7.4.2.  
Table 11 The variation in the error curve after the continuous durability test  
Flow rate  Maximum erro r limit 
of variation curves  
Class 1  Class 2  
Q1 ≤ Q＜Q2 ±2 ％ ±3 ％ 
Q2 ≤ Q ≤ Q4 ±1 ％ ±1.5 ％ 
7.9.3 others  
The same meters shall be submitted to the discontinuous and continuous tests and the test  
order shall not be changed. As specified in Table 12.  
Table 12 Summary of discontinuous, continuous tests  
Permane nt flow rate  Q3 m3/h ≤ 16  Q3 m3/h＞16 
Test flow rate Q3 Q4 Q3 Q4 
Test of type  discontinuous  continuous  continuous  continuous  
Number of interrupts  100,000  － － － 
Time of pauses  15 s － － － 
Time of test at test flow rate  15 s 100 h  800 h  200 h  
Duration of start-up and rundown  0.15[ Q3]a s with a 
minimum of 1 s  － － － 
a  [Q3] is the number equal to the value of Q3 expressed in m3/h. 
7.10 Magnetic field testing  
7.10.1  All water meters where the mechanical components may be influenced by a static magnetic 
field (e.g. equipped with a magnetic coupling in the drive to the readout or with a 
magnet -driven pulse output) and all meters  with electronic components shall be tested to 
show that they are able to withstand the influence of a static magnetic field. Equipmen t under 
test is measured at flow rate, Q1 and Q2. The relative errors  (of indication) shall not exceed 
the maximum permissible errors given in Table 1 in section 3.2.  
7.10.2 The magnetic field source for the test may be a permanent magnet or electric magne t and 
the intensity of the magnetic field shall be 1500 Gauss at the shell of meter. In a free space, 
the range of the values shall be within maximum permissible errors listed in Table 13.  CNPA 49  
 Page 26 of 55 
 Table 13 Quantified Intensity Distance Relation  
Distance from 
Maxim um 
Intensity Point  
mm Ratio to 1500 
Gauss Intensity  
% 
0 ≥100  
10 58.1 
20 36.0 
30 23.7 
40 16.4 
50 11.8 
60 8.7 
70 6.7 
7.10.3 The test points of a water meter tested are all located on the meter shell. Centered on the 
sensing magnet inside the meter as the reference point, test points are distributed  in a radial 
pattern as shown in Fig.7 and Fig.8. There are two adjacent test points and a central reference 
point. Points to be measured are at 45 -degree angle. There are 6 test points in total.  
 
Fig 7 Top View of Tested Meter  
 
Fig 8 Side View of Tested  Meter  
 CNPA 49  
 Page 27 of 55 
 7.10.4  Antimagnetic  function tests shall be performed according to above method and conditions 
and one for each symmetric test point. If there is any test point at which the indication errors 
of the tested meter exceed the maximum permissible error s for the flow -rate, the meter is 
failed in the test.  
8. Performance test of water meters eq uipped with electronic devices  
This section applies to water meters that based on electrical or electronic principles or mechanical 
principles incorporating electro nic devices.  
(q) Absence of flow test (Section 8.19)  
8.2 Reference  conditions  
8.2.1 Flow  rate 
0.7 x (Q2+ Q3) ± 0.03 x (Q2+ Q3) 
8.2.2 Water temperature  
25 ℃  ± 10 ℃  
8.2.3 Water pressure  
0.03 M Pa (0.3 bar)  to1 MPa  (10 ba r) 
8.2.4 Ambient temperature range  
15 ℃ to 35 ℃  
8.2.5 Ambient relative humidity range  
45 % to 95 %  
8.2.6 Ambi ent atmospheric pressure range  
86 kPa to 106 kPa  (0.86 bar  to 1.06 bar)  
8.2.7 Power supply voltage  (mains AC)  8.1 Tests involving the electronic  part of a water meter or its devices  
(a) Dry heat  (Section 8.4)  
(b) Cold  (Section 8.5)  
(c) Damp heat, cyclic  (Section 8.6)  
(d) Mains voltage variation  
(e) Powered by direct AC or by AC/DC converters (Section 8.7)  
(f) Water meters po wered by external DC voltage or by primary DC batteries (Section 8.8)  
(g) Interruption in battery supply  (Section 8.9)  
(h) AC mains voltage dips, short interruptions and voltage variations  (Section 8.10)  
(i) Bursts on signal lines  (Section 8.11)  
(j) Bursts (transients) on  AC and DC mains  (Section 8.12)  
(k) Electrostatic discharge  (Section 8.13)  
(l) Radiated electromagnetic fields  (Section 8.14)  
(m) Conducted electromagnetic fields  (Section 8.15)  
(n) Surges on signal, data and control lines  (Section 8.16)  
(o) Surges on AC and DC mains power li nes (Section 8.17)  
(p) Static magnetic field  (Section 8.18)  CNPA 49  
 Page 28 of 55 
 Nominal voltage, Unom± 5 %  
8.2.8 Powe r supply frequency  
Nominal frequency,  fnom± 2 %  
8.2.9 Power supply voltage (battery)  
A voltage V in the range Ubmin ≤ V ≤ Ubmax 
8.2.10 Test volumes for  measuring error (of indica tion) of a water meter  
For items not specified, the test volume for measuring the error of indication of the meter 
shall correspond to that delivered in 1 min at the overload flow rate Q4. 
8.3 Environmental classification  
8.3.1 Climatic  environmental classification  
8.3.1.1 Class B for fixed meters installed in a building.  
8.3.1.2 Class O for fixed meters installed outdoors.  
8.3.2 Electromagnetic  environments  
8.3.2.1 E1 – residential, commercial and light industrial . 
8.3.2.2 E2 – industrial.  
8.4 Dry heat  
Guidan ce on testing arrangements is given in IEC 60068 -3-1 and IEC 60068 -1. 
8.4.2 Test procedure  
8.4.2.1 Before cond itioning the water meter under test,  place the water meter at the reference 
air temperature of 25 °C ± 10 °C and calculate the relative error  (of indication) for each 
test condition in accordance with Section 8.2.  
8.4.2.2 Measure the error  (of indication) of the water meter under test at an air temperature of 
55 °C ± 2°C, after the water meter under test has been stabilized at this temperature for 
a period of 2 h . 
8.4.2.3 Measure the error  (of indication) of the water meter under test at the reference air 
temperature of 25 °C ± 5 °C, after recovery of the water meter under test.  
8.4.2.4 The water flo w direction of the water meter under test is specif ied in Section 7.4.3.  
8.4.3 Acceptance criteria  
8.4.3.1 A ll the functions of the water meter under test shall operate as designed;  
8.4.3.2 T he relative error  (of indication) of the water meter under test, at the test conditions, 
shall not exceed the maximu m permissible error of the upper flow rate zone in Table 1 
in Section 3.2.  
8.5 Cold  
Guidance on testing arrangements is given in IEC 60068 -3-1 and IEC 60068 -1. 
8.5.2 Test procedu re 8.4.1 Preparation  
Follow the test arrangements specified in IEC 60068 -2-2. 
8.5.1 Preparation  
Follow the testing arrangements specified in IEC 60068 -2-1. CNPA 49  
 Page 29 of 55 
 8.5.2.1 Do not pre -condition the water meter under test. Measure the error (of indication) of 
the water meter under test in accordance with Section 8.2 at the reference flow rate 
and at the reference air temperature of 25 ℃±10 ℃. 
8.5.2.2 Stabilize the air temperature at 10  °C ± 3  °C for a period of 2 h.  
8.5.2.3 Measure the error (of indication) of the water meter under test at the reference flow 
rate at an air temperature of 10  °C ± 3  °C. 
8.5.2.4 After recovery of the water  meter under test, measure the error  (of indication) of the 
water meter under test at the reference flow rate and at the reference air temperature.  
8.5.2.5 The water flow  direction of the water meter under test is specified in Section 7.4.3.  
8.5.3 Acceptan ce criteria  
8.5.3.1 A ll the functio ns of the water meter under test shall operate as designed; and  
8.5.3.2 T he relative error  (of indication) of the water meter under test, at the test conditions, 
shall not exceed the ma ximum permissible error of the upper  flow rate zone in Table 1 
in Section 3.2.  
8.6 Damp heat , cyclic  
Two 24 -hour cycles, each cycle includes Sections 8.6 .2.1 to Sections 8.6.2.5.  
8.6.2 Test procedure  
8.6.2.1 Pre-condition the water meter under test. Expose the water meter under test at 
temperature of 25  °C ± 3  °C and maintain the relative humidity above 95 %.  
8.6.2.2 Temperature rise to 55  °C ± 2  °C over 3  h. 
8.6.2.3 Temperature maintained at upper value and maintain the relative humidity above 95 
% until 12 h from the start of the cycle.  
8.6.2.4 Temperature taken down to the lower value within 3 h to 6 h, the rate of fall during 
the first 1 h 30 min being such that the temperature of 25 °C ± 3 °C would be reached 
in 3 h.  
8.6.2.5 Temperature maintained at 25 °C ± 3 °C and the relative humidity of 93% ± 3 %  until 
the 24 h cycle is completed.  
8.6.2.6 Allow the water meter under test  to recover. After recovery,  all parts of the water 
meter under test  are within 3 °C of their final temperature. Measure the error  (of 
indication) of the water meter under test  at the reference flow rate.  
8.6.2.7  The water fl ow direction of the water meter under test is specified in Section 7.4.3.  
8.6.3 Acceptance  criteria  
8.6.3.1 A ll the functions of the water meter under test shall operate as designed . 
8.6.3.2 Either  the difference between any indication before the test and the indication after 
the test shall not exceed one -half of the maximum permissible error in the upper flow 
rate zone in Table 1 in Section 3.2 or the water meter under test shall detect and act 8.6.1 Preparation  
Follow the testing arrangements specified in IEC 60068 -2-30. 
Guidance on testing arrangements is given in IEC 60068 -3-4. CNPA 49  
 Page 30 of 55 
 upon a significant fault.  
8.7 Power supply variation - Water meters powered by direct AC or by AC/DC converters  
8.7.1 Preparation  
Follow the testing arrangements specified in IEC 61000 -4-11, IEC 61000 -2-1, IEC 61000 -2-2, 
IEC 61000 -4-1, and IEC 60654 -2. 
8.7.2 Test procedure  
8.7.2.1 Measure the error  (of indication) of the water meter under test during the application 
of the up per mains  voltage limit, Unom + 10 % . 
8.7.2.2 Measure the error  (of indication) of the water meter under test during the application 
of the upper mains  frequency limit, fnom + 2 %.  
8.7.2.3 Measure the error  (of indication) of the water meter under test dur ing the application 
of the lower mains voltage limit, Unom − 15 % . 
8.7.2.4 Measure the error  (of indication) of the water meter under test during the application 
of the lower mains frequency limit, fnom − 2 %. 
8.7.3 Acceptance criteria  
8.7.3.1 A ll the func tions of the water meter under test shall operate as desig ned; 
8.7.3.2 The relative e rror of indication of the water meter under test, at the test conditions, 
shall not exceed the maximum permissible error of the upper flow rate zone in Table 1 
in Section 3.2.  
8.8 Power supply variation - Water meters powered by e xternal DC voltage or by primary DC batteries  
8.8.1  Test procedure  
8.8.1.1 Measure the error  (of indication) of the water meter under test, during the application 
of the maximum operating  voltage of the battery, as specified by the water meter 
supplier, fo r a battery or the DC voltage at which the water meter under test has been 
manufactured to automatically detect high -level conditions for an external DC supply.  
8.8.1.2 Measure the  error  (of indication) of the water meter under test, during the application  
of the minimum operating voltage of the battery, as specified by the water meter 
supplier, for a battery or the DC voltage at which the water meter under test has been 
manufactured to automatically detect low -level conditions for an external DC supply.  
8.8.2 Acceptance criteria  
8.8.2.1 A ll the functions of the water meter under test shall operate as designed;  
8.8.2.2 T he re lative error  (of indication) of the water meter under test at the test conditions 
shall not exceed the maximum permissible error of the  upper flow rate zone in Table 1 
in Section 3.2.  
8.9 Power supply variation - Interruption in battery supply  
This section applies only to water meters with replaceable batteries.  
8.9.1 Test procedure  
8.9.1.1  Remove the battery . 
8.9.1.2  A period of 1 h afte r remove the battery and then reconnect it.  CNPA 49  
 Page 31 of 55 
 8.9.1.3  Interroga te the functions of the meter.  
8.9.2 Acceptance criteria  
8.9.2.1 All the functions of the water meter under test shall operate as designed;  
8.9.2.2 T he value of the totalization or the stored val ues shall remain unchanged.  
8.10 AC mains v oltage dips, short interruptions  and voltage variations  
The test in this section is only applicable to the water meter with external AC power supply . 
8.10.1 Preparation  
Follow the testing arrangements specified in  IEC 61000 -4-11, IEC 61000 -6-1, and IEC 
61000 -6-2. 
8.10.2 Test procedure  
8.10.2.1 Measure the error  (of indication) of the water meter under test in accordance with 
Section 8.2 before applying power reduction test.  
8.10.2.2 Measure the error  (of indication ) of the water meter under test in accordance with 
Section 8.2 during the application of at least 10 voltage interruptions and 10 voltage 
reductions with an interval of at least 10 s.  
8.10.2.3 A test generator is used which is suitable to reduce the amplit ude of the AC mains 
voltage for a defined period of time.  The performance of the test generator shall be 
verified before connecting the water meter under test.  
8.10.2.4 V oltage interruptions and voltage reductions are applied throughout the period 
required  to measure the error  (of indication) of the water meter under test. V oltage 
interruptions: the supply voltage is reduced from its nominal value, U nom, to zero 
voltage, for the duration of 300 cycles  (60 Hz). V oltage interruptions are applied in 
groups of 10. 
8.10.2.5  V oltage reductions: the supply voltage is reduced from nominal voltage to zero 
voltage, for the duration of 0.5 cycles  (60 Hz); reduced from nominal voltage to zero 
voltage, for the duration of 1 cycle  (60 Hz); and reduced from nominal voltage  to 70  
% voltage, for the duration of 30 cycles  (60 Hz). V oltage reductions are applied in 
groups of 10.  
8.10.2.6  The water flow direction of the water meter under test is specified in Section 7.4.3.  
8.10.3  Acceptance criteria  
8.10.3.1 All the functions of  the water meter under test shall operate as designed;  
8.10.3.2  The difference between the relative error  (of indication) obtained during the 
application of the short time power reductions and that obtained at the same flow rate 
before the test, under  reference conditions, shall not exceed one -half of the maximum 
permissible error in the upper flow rate zone in Table 1 in Section 3.2  or the water 
meter under test  shall detect and act upon a significant fault.  
8.11 Burst s on signal lines  CNPA 49  
 Page 32 of 55 
 To verify that a water meter containing electronics and provided with input/output (I/O) and 
communication ports  (including its external cables).  
8.11.2  Test procedure  
8.11.2.1  Measure the error  (of indication) of the water meter under test in accordance with 
Section 8.2 before  applying the electrical bursts.  
8.11.2.2  Measure the error  (of indication) of the water meter under test in accordance with 
Section 8.2 during the applicati on of bursts of transient voltage spikes, of double 
exponential waveform.  
8.11.2.3  A burst generator shall be used with the performance characteristics as specified in 
the cited standard.  
8.11.2.4  Each spike  shall have an amplitude  (positive or negative) o f 0.5 kV for 
environmental class E1 instruments or 1 kV for environmental class E2 instruments, 
phased randomly, with a rise time of 5 ns and a half amplitude duration of 50 ns.  
8.11.2.5  The burst length shall be 15 ms and the burst repetition rate shall b e 5 kHz.  
8.11.2.6  The injection network on the mains shall contain blocking filters to prevent the burst 
energy from being dissipated in the mains.  
8.11.2.7  For the coupling of the bursts into the I/O and communication lines, a capacitive 
coupling clamp as  defined in the standard shall be used.  
8.11.2.8  The dura tion of the test shall not be less than 1 min for each amplitude and polarity.  
8.11.2.9  The water flow direction of the water meter under test is specified in Section 7.4.3.  
8.11.3  Acceptance criteri a 
8.11.3.1  After  the application of the disturbance, all the functions of the water meter under 
test shall operate as designed . 
8.11.3.2  The difference between the relative error of indication, obtained during the 
application of the burst s and that obtaine d at the same flow rate before the test, under 
reference conditions, shall not exceed one -half of the maximum permissible error in 
the upper flow rate zone  in Table 1 in Section 3.2  or the water meter under test  shall 
detect and act upon a significant faul t. 
8.12 Bursts  (transients) on AC and DC mains  
8.12.2  Test procedure  
8.12.2.1  Measure th e error  (of indication) of the water meter under test in accordance wit h 
Section 8.2 before applying the electrical bursts.  
8.12.2.2  Measure the error (of indication) of the water meter under test in accordance with 
Section 8.2 during the application of bursts of transient voltage spikes, of double 
exponential waveform.  8.11.1  Preparation  
Follow the testing arrangements specified in IEC 61000 -4-4 and IEC 61000 -4-1. 
8.12.1  Preparation  
Follow the testing arrangemen ts specified in IEC 61000 -4-4 and IEC 61000 -4-1. CNPA 49  
 Page 33 of 55 
 8.12. 2.3 A burst generator shall be used with the performance characteristics as specified in 
the cited standard.  
8.12.2.4  Each spike shall have an amplitude (positive or negative) of 1 kV for environmental 
class E1 instruments or 2 kV for environmental class E 2 instruments, phased 
randomly, with a rise time of 5 ns and a half amplitude duration of 50 ns.  
8.12.2.5  The burst length shall be 15 ms and the burst repetition rate shall be 5 kHz.  
8.12.2.6  The water flow direction of the water meter under test is speci fied in Section 7.4.3.  
8.12.3  Acceptance criteria  
8.12.3.1 After the ap plication of the disturbance, all the functions of the water meter under 
test shall operate as designed . 
8.12.3.2 The differenc e between the relative error of indication, obtained durin g the 
application of the bursts and that obtained at the same flow rate before the test, under 
reference conditions , shall not exceed one -half of the maximum permissible error in 
the upper flow rate zone  in Table 1 in Section 3.2  or the water meter under t est shall 
detect and act upon a significant fault.  
8.13 Electrostatic discharge  
8.13.1  Preparation  
Follow the testing arrangements specified in IEC 61000 -4-2. 
8.13.2 Test procedure  
8.13.2.1 Measure t he error (of indication) of the water meter under test in  accordance with 
Section 8.2 before applyi ng the electrostatic discharges.  
8.13.2.2  Charge a 150 pF capacitor by means of a suitable DC voltage source, then discharge 
the capacitor through the water meter under test by connecting one terminal of the 
suppor ting chassis to ea rth and the other via a 330 Ω resistor to surfaces of the water 
meter under test which are normally accessible to the operator. If there has a coating 
of the water meter under test, the coating must be scratched off at the test point befo re 
test. 
8.13.2.3  For each contact discharge, a voltage of 6 kV shall be applied; for each air discharge, 
a voltage o f 8 kV shall be applied;  
8.13.2.4  At each test location, at least 10 direct discharges shall be applied at intervals of at 
least 10 s betwe en discharges, during the same measurement or simulated 
measurement; for indirect discharges, a total of 10 discharges shall be applied on the 
horizontal coupling plane and a total of 10 discharges for each of the various positions 
of the vertical coupling  plane.  
8.13.2.5 Measure the error (of indication) of the water meter under test during the application 
of electrostatic discharges . 
8.13.2.6 For water meter under test not equipped with an earth terminal, the water meter 
under test shall be fully discharg ed between discharges.  
8.13.2.7 Contact discharge is the preferred test method. Air discharges shall be used where CNPA 49  
 Page 34 of 55 
 contact discharge cannot be applied.  
8.13.2.8 The water  flow directi on of the water meter under test is specified in Section 7.4.3.  
8.13.3  Acceptance criteria  
8.13.3.1 After the ap plication of the disturbance, all the functions of the water meter under 
test shall operate as designed.  
8.13.3.2  The difference between the relative error (of indication), obtained during the 
application of the elect rostatic discharges and that obtained before the test, at the 
same flow rate, under reference conditions, shall not exceed one -half of the maximum 
permissible error in the upper flow rate zone  in Table 1 in Section 3.2  or the water 
meter under test  shall d etect and act upon a significant fault.  
8.14 Radiated electromagnetic fields  
8.14.1  Preparation  
Follow the testing arrangements specified in IEC 61000 -4-3. 
8.14.2 Test procedure  
8.14.2.1 Measure the intri nsic error (of indication) of the water meter under test in 
accordance with Section 8.2  before applying the electromagnetic field.  
8.14.2.2  The water meter under test , and its external cables of at least 1.2 m length, shall be 
subjected to radiate d electromagnetic fields at field strengths of either 3 V/m f or 
environmental class E1 instruments or 10 V/m for environmental  class E2 instruments. 
The test is performed as several partial scans with a vertical antenna and several 
partial scans with a horizontal antenna.  
Recommended start and stop frequencies for each scan are listed in Table 14. The 
frequency range for this radiated electromagnetic fields test is 26 MHz to 2 GHz, or 80 
MHz to 2 GHz when the test for frequencies in the lower range in Table 15 in Section 
8.15 is applicable.  CNPA 49  
 Page 35 of 55 
 Table 14 Start and stop carrier frequencies (Radiated electromagnetic fields)  
MHz  MHz  MHz  
26 160 600 
40 180 700 
60 200 800 
80 250 934 
100 350 1000  
120 400 1400  
144 435 2000  
150 500  
Note : Breakpoints are approximate.  
8.14.2.3  During each scan, the frequency shall be cha nged in steps of 1 % of actual frequency, 
until the next frequency in Table 4 is reached. The dwell time at each 1 % step shall 
be identical. However , the dwell time shall be equal for all carrier frequencies in the 
scan and shall be sufficient for the  water meter under test  to be exercised and able to 
respond at each frequency. The error (of indication) measurements shall be carried out 
with all of the scans listed in Table 14.  
8.14.2.4 Change the polarization of the antenna.  
8.14.2.5  Repeat steps in Secti on 8.14.2.3 until all the carrier frequencies listed in Table 14 are 
completed.  
8.14.2.6  The water flow direction of the water meter under test is specified in Section 7.4.3.  
8.14.3Acceptance criteria  
8.14.3.1 After the application of the disturbance, all the functions of the water meter under 
test shall operate as designed . 
8.14.3.2 The difference between the relative error (of indication) measured during the 
application of each carrier frequency band and that obtained at the same flow rate 
before the test , under reference conditions, shall not exceed one -half of the maximum 
permissible error in the upper flow rate zone  in Table 1 in Section 3.2  or the water 
meter under test  shall detect and act upon a significant fault.  
8.15 Conducted electromagnetic field s 
Where there are discrep ancies between this specification and IEC 61000 -4-6, this 
specification shall govern.  
8.15.2 Test procedure  
8.15.2.1  Measure the intrinsic error (of indication) of the  water meter under test in 
accordance  with Section 8.2  at reference conditions before applying the 8.15.1 Preparation  
Follow the testing arrangements specified in IEC 61000 -4-6. However, the test procedure 
specified in Section 8.15.2 is a modified procedur e from IEC . CNPA 49  
 Page 36 of 55 
 electromagnetic field.  
8.15.2.2  The water meter unde r test  shall be subjected to conducted electromagnetic fields at 
RF amplitude of either 3V for environmental class E1 instruments, or 10 V for 
environmental class E2 instruments. The frequency range for this conducted 
electromagnetic fields test in 0.15 MH z to 80 MHz. Recommended start and stop 
frequencies for each scan are listed in Table 15.  
8.15.2.3 During each scan, the frequency shall be changed in steps of 1 % of actual frequency. 
The dwell time at each 1 % step shall be identical. However, the dwell time shall be 
equal for all carrier frequencies in the scan and shall be sufficient for the water meter 
under test  to be exercised and able to respond at each frequency. The error (of 
indication) measurements shall be carried out with all of the scans list ed in Table 5.  
8.15.2.4  The water flow direction of the water meter under test is specified in Section 7.4.3.  
8.15.2.5  Repeat steps s in 8.15.2.3 until all the carrier frequencies listed in Table 15 are 
completed.  
Table 15 Start and stop carrier frequencie s (Conducted electromagnetic fields)  
MHz  MHz  MHz  
0.15 2.2 30 
0.30 3.9 50 
0.57 7.5 80 
1.1 14  
Note:  Break points are approximate.  
8.15.3  Acceptance criteria  
8.15.3.1  After the application of the disturbance, all the functions of the water meter under 
test shall operate as designed.  
8.15.3.2 The difference between the relative error (of indication) measured during the 
application of each carrier frequency band and that obtained at the same flow rate 
before the test, under reference conditions, shall not  exceed one -half of the maximum 
permissible error in the upper flow rate zone in Table 1 in Section 3.2  or the water 
meter under test  shall detect and act upon a significant fault.  
8.16 Surges on signal, data and control lines  
8.16.1  Preparation  
Follow the  testing arrangements specified in IEC 61000 -4-5. 
8.16.2  Test procedure  
8.16.2.1  Measure the error (of indication) of the water meter under test in accordance with 
Section 8.2  before applying the surges.  
8.16.2.2  The surges have to be applied line to line and line(s) to earth. When testing line to 
earth, the test voltage shall be applied successively between each of the lines and 
earth, if there is no other specification.  CNPA 49  
 Page 37 of 55 
 8.16.2.3  Measure the error (of indication) of the water meter under test  after the app lication 
of surge transient voltages . 
8.16.2.4  This test is only applicable for environmental class E2, for which the surge transient 
voltage on line to line is 1 kV , and on line to earth is 2 kV .  
8.16.2.5  The wa ter flow direction of the water meter under test is specified in Section 7.4.3.  
8.16.3  Acceptance criteria  
8.16.3.1  After the application of the disturbance, all the functions of the water meter under 
test shall operate as designed.  
8.16.3.2 The difference between the relative error of indication ob tained after the application 
of the surge transient voltages and that obtained before the test shall not exceed 
one-half of the MPE of the “upper zone“  in Table 1 in Section 3.2  or the water meter 
under test  shall detect and act upon a significant fault . 
8.17 Surges on AC and DC mains power lines  
8.17.1  Preparation  
Follow the testing arrangements specified in IEC 61000 -4-5. 
8.17.2  Test procedure  
8.17.2.1  Measure the error (of indication) of the water meter under test in accordance with 
Section 8.2 before ap plying the surge transient voltages.  
8.17.2.2  If not otherwise specified, the surges have to be applied synchronized to the voltage 
phase at the zero -crossing and the peak value of the AC voltage wave (positive and 
negative).  
8.17.2.3  The surges have to be  applied line to line and line(s) to earth. When testing line to 
earth the test voltage shall be applied successively between each of the lines and earth, 
if there is no other specification.  
8.17.2.4  Measure the error (of indication) of the water meter und er test  after the application 
of surge transient voltages . 
8.17.2.5  This test is only applicable for environmental class E2, for which the surge transient 
voltage on line to line is 1 kV , and on line to earth is 2 kV .  
8.17.2.6  On AC mains supply lines at l east three positive and three negative surges shall be 
applied synchronously with AC supply voltage in angles 0°, 90°, 180° and 270°.  
8.17.2.7  On DC power lines, at least three positive and three n egative surges shall be applied . 
8.17.2.8 The water flow di rection of the water meter under test is specified in Section 7.4.3.  
8.17.3  Acceptance criteria  
8.17.3.1  After the application of the disturbance, all the functions of the water meter under 
test shall operate as designed.  
8.17.3.2 The difference between th e relative error of indication obtained after the application 
of the surge transient voltages and that obtained before the test shall not exceed 
one-half of the MPE of the “upper zone”  in Table 1 in Section 3.2  or the water meter 
under test  shall detect an d act upon a significant fault.  CNPA 49  
 Page 38 of 55 
 8.18 Static magnetic field  
Test procedures, requirements and acceptance criteria are the same as in Section 7.10.  
8.19 Absence of flow test  
8.19.1 Test procedure  
8.19.1.1  Fill the meter with water, purging out all air.  
8.19. 1.2 Ensure there is no flow through the measurement transducer. Observe the meter 
index for 15 min.  
8.19.1.3  Fully discharge the water from the meter. Observe the meter index for 15 min.  
8.19.2  Acceptance criteria  
8.19.2.1  The water meter totalization shal l not change by more than the value of the 
verification scale interval during each test interval.  
9. Implementation date  
This specification will be implemented from July 1, 2023  for mechanical water meters, and for water 
meters with electronic devices from  January 1, 2026 ; the correction period ends on December 31, 2027 . CNPA 49  
 Page 39 of 55 
  
Appendix A Flow disturbers  
Machined dimensions shall have a tolerance of ±0.25 mm unless otherwise stated.  
A2. Threaded type disturbance generators  
 
Item  Description  Quantity  Material  
1 cover  1 stainless steel  
2 body  1 stainless steel  
3 swirl generat or 1 stainless steel  
4 flow  － － 
5 gasket  2 fibre  
6 hexagon socket 
head cap screw  4 stainless steel  
type 1 disturber – Sinistrorsal swirl generator;  
type 2 – Dextrorsal swirl generator  
Figure A.1 Threaded type disturbance generator – Arrangement of swir l generator units  
 
 
 A.1 General  
Figures A.1 to A.12 show flow disturber types to be used in tests as specified in Section 7.8.  
All dimensions shown in the drawings are in millimetr es, unless otherwise stated.  CNPA 49  
 Page 40 of 55 
 
 
Item  Description  Quantity  Material  
1 cover  1 stainless steel  
2 body  1 stainless steel  
3 flow  － － 
4 flow disturber  1 stainless steel  
5 gasket  2 fibre  
6 hexagon socket 
head cap screw  4 stainless steel  
type 3 disturber – Velocity  profile flow disturber  
Figure A.2 Threaded type disturbance generator – Arrangement of velocity profile disturbance units  
 
Key 
1  4 holes ϕJ, bore ϕK × L          Machined surface roughness 3.2 μm all over  
Figure A.3 Cover for a threaded type disturbance  generator, with dimensions as set out in Table A.1  
 
 
 
 
 CNPA 49  
 Page 41 of 55 
 Table A.1 Dimensions for the cover (item 1) for a threaded type disturbance generator  
unit：mm 
threaded type disturbance generator －item 1：cover  
DN A B(e9a) C D E(b) F G H J K L M N 
15 52 29.960  
29.908 23 15 G3/4〞B 10 12.5 5.5 4.5 7.5 4 40 23 
20 58 35.950  
35.888  29 20 G1〞B 10 12.5 5.5 4.5 7.5 4 46 23 
25 63 41.950  
41.888  36 25 G1 1/4〞B 12 14.5 6.5 5.5 9.0 5 52 26 
32 76 51.940  
51.866  44 32 G1 1/2〞B 12 16.5 6.5 5.5 9.0 5 64 28 
40 82 59.940  
59.866  50 40 G2〞B 13 18.5 6.5 5.5 9.0 5 70 30 
50 102 69.940  
69.866  62 50 G2 1/2〞B 13 20.0 8.0 6.5 10.5 6 84 33 
key( a )See ISO 286 -2.   (b)See ISO 228 -1. 
 
Key 
1  4 holes ϕH × J deep. Tap K thread × L 
Machined surface roughness 3.2 μm all over  
Figure A.4 Body of a threaded type disturbance generator, with dimensions as set out in Table A.2  
 
 
 
 
 
 
 
 
 
 CNPA 49  
 Page 42 of 55 
 Table A.2 Dimensions for the body (item 2) of a threaded type disturbance generator  
unit：mm 
threaded type disturbance generator －item 2：body  
DN A B(H9(a)) C D E F G H J K L M 
15 52 30.052  
30.000  23.5 15.5 15 46 G3/4〞B 3.3 16 M4 12 40 
20 58 36.062  
36.000  26.0 18.0 15 46 G1〞B 3.3 16 M4 12 46 
25 63 42.062  
42.000  30.5 20.5 20 55 G1 1/4〞B 4.2 18 M5 14 52 
32 76 52.074  
52.000  35.0 24.0 20 65 G1 1/2〞B 4.2 18 M5 14 64 
40 82 60.074  
60.000  41.0 28.0 25 75 G2〞B 4.2 18 M5 14 70 
50 102 70.074  
70.000  47.0 33.0 25 90 G2 1/2〞B 5.0 24 M6 20 84 
Key ( a )  See ISO 286 -2. 
 
Key 
1  8 slots equally spaced to locate blades      2   locate blades in slots and welding   
3  depth of slot at cent re, 0.76                4   blade detail  
Machined surface roughness 3.2 μm all over  
Figure A.5 Swirl generator for a thre aded type disturbance generator  
 
 
 
 
 
 
 
 
 
 
 CNPA 49  
 Page 43 of 55 
 Table A.3 Dimensions for the swirl generator (item 3) of a threaded type disturbance generato r 
unit：mm 
threaded type disturbance generator －item 3：swirl generator  
DN A(d10(a)) B C D E F G H J 
15 29.935  
29.851  25 15 10.5  7.5 6.05  7.6 0.57  
0.52  0.50  
20 35.920  
35.820  31 20 13.0  10.0  7.72  10.2  0.57  
0.52  0.50  
25 41.920  
41.820  38 25 15.5  12.5  9.38  12.7 0.82  
0.77  0.75  
32 51.900  
51.780  46 32 19.0  16.0  11.72  16.4  0.82  
0.77  0.75  
40 59.900  
59.780  52 40 23.0  20.0  14.38  20.5  0.82  
0.77  0.75  
50 69.900  
69.780  64 50 28.0  25.0  17.72  25.5  1.57  
1.52  1.50  
Key ( a )  See ISO 286 -2. 
 
Machined surface roughness 3.2 μm all over  
Figure A.6 Flow disturber for a threaded type disturbance generator  
Table A.4 Dimensions for the flow disturber (item 4) of a threaded type disturbance generator  
unit：mm 
threaded type disturbance generator －item 4：Flow disturber  
DN A(d10(a)) B C D E F G 
15 29.935  
29.851  25 15 13.125  10.5  7.5 7.5 
20 35.920  
35.820  31 20 17.500  13.0  10.0  5.0 
25 41.920  
41.820  38 25 21.875  15.5  12.5  6.0 
32 51.900  
51.780  46 32 28.000  19.0  16.0  6.0 
40 59.900  
59.780  52 40 35.000  23.0  20.0  6.0 
50 69.900  
69.780  64 50 43.750  28.0  25.0  6.0 
Key ( a )  See ISO 286 -2. CNPA 49  
 Page 44 of 55 
 
 
Figure A.7 Gasket for a threaded type disturbance generator  
unit：mm 
threaded type disturbance generator －item 5：gasket  
DN A B 
15 24.5  15.5  
20 30.5  20.5  
25 37.5  25.5  
32 45.5  32.5  
40 51.5  40.5  
50 63.5  50.5  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Table A.5 Dimensions for the gasket (item 5) of a threaded type disturbance generator  CNPA 49  
 Page 45 of 55 
 A.3  Wafer type disturbance generators  
 
Item Description  Quantity  Material  
1 swirl generato r 1 stainless steel  
2 flow  － － 
3 gasket  2 fibre  
4 straight length with flange  
(ISO 7005 -2or ISO 7005 -3) 4 stainless steel  
type 1 disturber – Swirl generator sinistrorsal;  
type 2 disturber – Swirl generator dextrorsal  
Figure A.8 Wafer type disturbance g enerators – Arrangement of swirl generator unit  
 
Item Description  Quantity  Material  
1 flow disturber  1 stainless steel  
2 flow  － － 
3 gasket  2 fibre  
4 straight length with flange  
(ISO 7005 -2or ISO 7005 -3) 4 stainless steel  
type 3 disturber – Velocity p rofile flow disturber  
Figure A.9 Wafer type disturbance generator – Arrangement of velocity profile disturbance units  CNPA 49  
 Page 46 of 55 
 
 
Key 
1  8 slots equally spaced to locate blades   
2  blades to be fixed in (welding)  
3  blade detail  
Figure A.10 Swirl generator for wafer  type disturbance generator  
 
Table A.6 Dimensions for the swirl generator (item 1) of a wafer type disturbance generator  
unit：mm 
DN  A  B  C  D  E  F  G  H  J  K  L  M  N  P  R  
50  50  165  104  4  18  125  45°  25  28  16.9  25.5  1.5  1.57 1.52  —  —  
65  65  185  124  4  18  145  45°  33  36  21.9  33.4  1.5  1.57 1.52  —  —  
80  80  200  139  8  18  160  22 1/2 °  40  43  26.9  40.6 1.5  1.57 1.52  —  —  
100  100  220  159  8  18  180  22 1/2 °  50  53  33.6  50.8  1.5  1.57 1.52  —  —  
125  125  250  189  8  18  210  22 1/2 °  63  66  41.9  64.1  1.5  1.57 1.52  —  —  
150  150  285  214  8  22  240  22 1/2 °  75  78  50.3  76.1  3.0  3.07 3.02  195  22  
200  200  340  269  8  22  295  22 1/2 °  100  103  66.9  101.6  3.0  3.07 3.02  245  24  
250  250  395  324  12  22  350  15°  125  128  83.6  127.2  3.0  3.07 3.02  295  26  
300  300  445  374  12  22  400  15°  150  153  100.3  152.7  3.0  3.07 3.02  345  28  
400  400  565  482  16  27  515  11 1/4 °  200  203  133.6  203.8  3.0  3.07 3.02  445  30  
500  500  670  587  20  27  620  9°  250  253  166.9  255.0  3.0  3.07 3.02  545  32  
600  600  780  687  20  30  725  9°  300  303  200.3  306.1  3.0  3.07 3.02  645  34  
800  800  1015  912  24  33  950  7 1/2 °  400  403  266.9  408.3  3.0  3.07 3.02  845  36  
 CNPA 49  
 Page 47 of 55 
 
 
Key 
1 D holes of ϕE                              Machined surface roughness 3.2 μm all over  
Figure A.11 Flow disturber of a wafer type disturbance generator  
 
Table A.7 Dimensions for flow disturber (item 2) of a wafer type disturbance generator  
unit：mm 
wafer type disturban ce generator －item 2: flow disturber  
DN A B C D E F G H 
50 50 165 104 4 18 125 45° 43.8  
65 65 185 124 4 18 145 45° 56.9  
80 80 200 139 8 18 160 22 1/2°  70.0  
100 100 220 159 8 18 180 22 1/2°  87.5  
125 125 250 189 8 18 210 22 1/2°  109.4  
150 150 285 214 8 22 240 22 1/2°  131.3  
200 200 340 269 8 22 295 22 1/2°  175.0  
250 250 395 324 12 22 350 15° 218.8  
300 300 445 374 12 22 400 15° 262.5  
400 400 565 482 16 27 515 11 1/4°  350.0  
500 500 670 587 20 27 620 9° 437.5  
600 600 780 687 20 30 725 9° 525.0  
800 800 1015  912 24 33 950 7 1/2°  700.0  CNPA 49  
 Page 48 of 55 
 
 
Figure A.12 Gasket of a wafer type disturbance generator  
 
Table A.8 Dimensions for the gasket (item 3) of a wafer type disturbance generator  
unit：mm 
wafer type disturbance 
generator －item 3：gasket  
DN A B 
50 103.5  50.5  
65 123.5  65.5  
80 138.5  80.5  
100 158.5  100.5  
125 188.5  125.5  
150 213.5  150.5  
200 268.5  200.5  
250 323.5  250.5  
300 373.5  300.5  
400 481.5  400.5  
500 586.5  500.5  
600 686.5  600.5  
800 911.5  800.5  CNPA 49  
 Page 49 of 55 
 Appendix B The diameter and overall size of volumetric and velocity 
meter  
B.1 Diameter and overall dimension  
The diameter of water meter is characterized by the thread size of the end connections or by the 
nominal size of the flange. Fo r each meter size there is a corresponding fixed set of overall 
dimensions (see Figure B.1). The dimensions are giving in table B. 1 and B. 2. For thread and 
connections, two minimum dimensions, a and b, are specified (see B.1.3).  
H1+H 2, L, W1+W2 define the height, length and width respectively of a cuboid within which the 
water meter can be contained (the cover being at right angles to its closed position).  
H1, H 2, L, W1, W2 are maximum dimensions.  
 
Key  1 Pipe axis  
Figure B.1 – Meter size and overall dimen sion 
B.1.1  Permanent flow rate  Q3, expressed in m3/h. 
B.1.2  Relationship  between meter diameter and meter designation  
Meter diameter and hence overall dimensions are in principle linked to the designation of the 
water meter as specified in Tables B.1 and B .2. For a given meter diameter, it nevertheless is 
permitted to adopt the immediately adjacent larger or smaller meter diameter, provided that the 
metrological requirements are met. End connections shall be the same at the water meter inlet 
and outlet . 
Table B.1 Water meters with threaded end connections -Meter sizes and dimensions  
unit：mm 
Meter size  Meter dimensions  
Nominal 
Diameter  
DN Meter diameter 
(nominal size of 
threaded end 
connection  amin bmin Lmax W1max 
and 
W2max H1max H2max 
15(13)  G 3/4 B(3) 10 12 165 50 40 100 
20 G 1 B(3) 12 14 190 65 40 100 
25 G 1 1/4 B  12 16 210 85 45 110 
40 G 2 B  13 20 245 85 50 140 
50 G 2 1/2 B  13 20 270 115 60 180 
(3) thread size of the next larger value is accepted as an alternative.   CNPA 49  
 Page 50 of 55 
  
Table B.2 – Water meters with flanged end connection – Meter designations, meter sizes and dimension  Meter dimens ion ( unit: millimeter s) 
H2max 
Woltmann  
390 
39 
410 
440 
440 
500 
500 
500 
500 
Note:  (1) Nominal size of flange end connections.  V olumetric
, single -jet 
and 
multi -jet 
300 
320 
320 
320 
- 
 
 
 
 H1max 
Woltmann  
Horizon 
axis 
100 
110 
120 
140 
140 
180 
200 
220 
250 Vertical 
axis 
140 
- 
170 
180 
- 
220 
255 
270 
2850  V olumetric
, single -jet 
and 
multi -jet 
115 
130 
140 
215 
- 
 
 
 
 W1max and W2max 
Woltmann  
Horizon 
axis 
135 
135 
135 
135 
135 
175 
190 
210 
240 Vertical 
axis 
135 
- 
135 
135 
- 
180 
225 
250 
290 V olumetric
, single -jet 
and 
multi -jet 
135 
150 
170 
225 
- 
 
 
 
 Lmax 
Woltmann  
Horizon 
axis 
200 
300 
200 
250 
250 
300 
350 
450 
500 Vertical 
axis 
560 
- 
630 
750 
- 
1000  
1160  
1240  
1600  V olumetric
, single -jet 
and 
multi -jet 
350 
450 
480 
650 
- 
 
 
 
 Meter size  
Size 
DN (1) 
50 
65 
75 
100 
125 
150 
200 
250 
300 
B.1.3  Threaded connection  
Values are given in table B.1. Threads shall comply with CNS 494. Figure B.2 defines 
dimensions a and b. When there is installation problem for replacing new water meter, the 
threads specified i n Section B.2 may be adopted.  CNPA 49  
 Page 51 of 55 
 
 
Figure B.2 - Thread  
B.1.4  Flanged connection  
Either one of the following specification of flange shall be adopted.  
B.1.4.1  Flanged end connections shall comply with table A.2 for working pressure 0.735 MPa of 
CNS 12795 or CN S 13272, and the flange size is in accordance with the prov isions of 
Table 2 of CNS 12795 . The manufacturer shall provide a reasonable clearance behind the 
rear face of the flange to allow access for installation and removal.  
B.1.4.2  The flange connection end face adopts the flange size of other specifications of working 
pressure. However, the applicant shall provide the connection adaptor for type approval 
testing. The manufacturer shall provide a reasonable clearance behind the rear face of the 
flange to allow access for installation and removal.  
B.2 The thread specification of threaded connecting of water meters.  
B.2.1  Type  
The thread type of threaded connecting of water meters are divided into two types, male pipe 
thread and female pipe thread . 
B.2.2 Dimension  
The dimension of thread is described in Table B.3, the basic profile of and basic dimension is 
described B.4 and the tolerance of dimension is described in Table B.5.  
 CNPA 49  
 Page 52 of 55 
 Table  B.3 Dimension of thread of water mete  
 
 
Nominal 
Diameter  
mm Outside 
diame ter of 
water 
meter d  
mm Number of 
Threads 
per 25.4 
mm a 
(minimum)  
mm 
15(13)  25.8 14 14 
20 33.0 14 14 
25 39.0 14 14 
4. 56.0 11 18 
50 67.6 11 18 
 CNPA 49  
 Page 53 of 55 
 Table B.4 Thread profile  
 
A: external thread  
B: internal thread  
unit: mm  
The basic profile of threads in this table is according to CNS 494  Nominal 
Diameter  Number 
of Threads 
per 25.4 
mm Pitch  Height 
of 
thread  Radius of 
rounded 
crests and 
roots  Diameters of external thread  
Major d  Pitch d 2 Minor d 1 
Diameters of internal thread  
Major D  Pitch D 2 Minor D 1 
15(13)  14 1.8143  1.162  0.25 25.8 24.64  23.48  
20 14 1.8143  1.162  0.25 33.0 31.81  30.68  
25 14 1.8143  1.162  0.25 39.0 37.84  36.67  
40 11 2.3091  1.479  0.32 56.0 54.52  53.04  
50 11 2.3091  1.479  0.32 67.6 66.12  64.64  Axis of thread  
d2 or D2 d1 or D1 
d or D  Solid-line 
indicates  
 the profile of 
thread  
n4.25P
 
H=0.960491P  
h=0.640327P  
r=0.137329P  
d2=d-h   D2=d2 
d1=d-2h  D1=d1 A B CNPA 49  
 Page 54 of 55 
 Table B.5 Deviation of dimension  
 
 
 
 
 
 
 
 
 
 
 
 
 
A: external thread  
B: internal thread  
Nominal 
Diameter  
 mm Number 
of 
Threads 
per 25.4 
mm Tolerance on the pitch of external thread  
 μm Tolerance on the pitch of internal thread  
 μm 
Major d  Pitch (1) d2 Minor d 1 Major D  Pitch (1) D 2 Minor D 1 
Upper 
deviation  Lower 
deviation 
( - ) Upper 
deviation  Lower 
deviation 
( - ) Lower 
deviation  Upper 
deviation  Lower 
deviation  Upper 
deviation  Lower 
deviation  Upper 
deviation 
( + ) Lower 
deviation  Upper 
deviation 
( + ) 
15(13)  14 0 284 0 284 0 No 
specified  0 No 
specified  0 142 0 541 
20 14 0 360 0 360 0 0 0 180 0 640 
25 14 0 360 0 360 0 0 0 180 0 640 
40 11 0 360 0 360 0 0 0 180 0 640 
50 11 0 434 0 434 0 0 0 217 0 640 
Note: (1) For thin -walled parts, the tolerances apply to the mean pitch diameter, which is the 
arithmetical mean of two diameters measured at right angles to each other.  
1. The deviations specified in this table are accordi ng to B Class of CNS 494.  
2. The deviations of half angle of thread and the pitch dimension that not specified in this table 
have been converted into diametral pitch and included in the tolerance of pitch.  
 
 
 
 
 
 
 
(Upper deviation of pitch diameter of 
internal thread )×
21  
(Upper deviation of minor diameter of 
internal thread)×
21  
(Lower deviation of pitch diameter of 
external thread )×
21 (Lower deviation of major diameter of 
external thread )×
21  
Axis of thread  A B CNPA 49  
 Page 55 of 55 
  
Annex  C Vortex water meter diameter and sh ape dimensions  
C.1 Diam eter and overall size of meters  
The structure of meters are described as Figure C.1, the overall size and flow -rates are described as 
Table C.1. Unspecified structure and dimension mat be decided by manufacturers.  
 
Figure C.1 The fl ange dimension of V ortex water meters  
 
Table C.1 – The flow -rate and dimension of vortex meters  
 Specification  
 
 
Nominal 
Diameter  
(DN)  
mm V ortex water meters  
Maximum 
flow-rate 
(m3/h) ≥ Minimum 
flow-rate 
(m3/h) ≤ L 
(unit: mm)  
≤  Button to 
Center of 
Bore(H 1) 
mm 
 ≤ Top to 
Center of 
Bore(H 2) 
mm 
 ≤ 
50 60 6 170 100 390 
75 160 16 190 120 410 
100 250 25 210 140 440 
Note 1. The flow -rates listed in the table are based on the working medium  (water)  with dynamic 
viscosity 1 x 10-6 m2/s. 
2. The dimension D 2 and d  x n of the flanges are specified in CNS 12795 or CNS 13727.