**1. Introduction**

In line with the Measurement Protocol for Water Meters in the Republic of Serbia, a water meter is declared unreliable for water volume measuring at flow rates lower than Qmin [1-3]. For a 20 mm rated diameter water meter, used in the households of this country, the mini‐ mum flow is about Qmin=0.016-0.060 m3 /hour. Therefore, water volume is measured unrelia‐ bly due to leakage at the tap, with a flow of 0.003-0.007 m3 /h (drop by drop) and 0.010-0.016 m3 /h (jet), at the bathroom tap at 0.010-0.014 m3 /h (in a very thin jet), and at the toilet tank at 0.004-0.025 m3 /h. As a solution to this problem, the installation of impulse valve, unmeas‐ ured-flow reducer, known as UFR, at the water meter is recommended since 2007.

UFR operates based on the difference between the upstream and downstream pressure of 0,4 bar at the valve. For pressure lower than the declared, the UFR closes flow through the water meter, since the spring force is stronger than the force generated by the difference in upstream and downstream pressure. Due to water losses through pipeline leakage, the dif‐ ference in pressure exceeds the limit value, hence the UFR opens, providing flow at a rate of at least Qmin which is then registered by the water meter. UFR manufactured by A.R.I. from Jerusalem is used for adjusting water volume measuring at flow rates lower than 0.026 m3 /h.

The papers published so far refer to measurements obtained on individual water meters and on segments of pipelines.

Operation of 33 water meters with UFR was tested in a calibration laboratory in Udine (Ita‐ ly) [5]. The water meters had a rated diameter of 20 mm, class C, Qmin=0.025 m3 /h, each 1 to 7

© 2013 Hovany; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

years old. In joint operation of water meters with URF a higher water volume was meas‐ ured: it was 94% in cases of stagnating water meter propellers, 31.8% for flow rates at the commencement of the propeller rotation (further designated as Qa) and 14.4% for Qmin. The valve's most significant contribution was defined for flow at water meter propeller still‐ stand. Due to the characteristics of water meters installed in the Republic of Serbia, a similar research is necessary for water meters with 0.025 m3 /h<Qmin<0.060 m3 /h.

measuring. During the operation with URF a higher water consumption was measured: 10.4% for July 2008, 9.5% for August 2008, 4.9% for September 2008, 11.9% for October 2008, 7.6% for November 2008, 8.9% for December 2008, 3.9% for January 2009, 8.4% for February

Error in Water Meter Measuring Due to Shorter Flow and Consumption Shorter Than the Time...

Two balancing were made on a part of the supply network with 52 water meters in Palermo: from October 24 through November 14, 2008 without UFR and from December 12, 2008 through January 9, 2009 with UFR [10]. The water meters with 15 mm rated diameter were either 11 years old (33, class C) or older (17 of class B and 2 of class A). During the operation with UFR, the measured volume of consumed water was higher for 28.06-18.91=9.15%.

The use of UFR facilitates the measuring of water consumption at flow rates lower than Qmin.

and that water consumption exceeds Qmin, a water supply network for a single household was set up in the Hydraulic Laboratory of the faculty of Civil Engineering in Subotica. The aim of the test was to confirm the contribution of UFR in measuring water volume by water

ARI from Jerusalem manufactures UFR with 20 mm rated diameter in three types, designed T10, T20 and T30. Thus, conclusions of testing with valve type T30 could also be controlled

> **Class Water Discharged Permitted Time between discharge water error two**

A Qmin=0.06 10 5 0.5 10

B Qmin=0.03 5 5 0.25 10

A Qmin=0.1 20 5 1 12

B Qmin=0.05 20 5 1 24

**Table 1.** Water volume and calibrated time of water meter of 20 mm rated diameter in the function of typical flows

**m3/h litres ±% ± litres minutes**

Qt=0.15 25 2 0.5 10 Qn=1.5 100 2 2 4

Qt=0.12 25 2 0.5 12.5 Qn=1.5 100 2 2 4

Qt=0.25 30 2 0.6 7.2 Qn=2.5 100 2 2 2.4

Qt=0.2 25 2 0.5 7.5 Qn=2.5 100 2 2 2.4

/h<Qmin<0.060 m3

**volume limit readings**

/h.

http://dx.doi.org/10.5772/51046

/h

133

By fulfilling the condition, that the flow of supply network water losses is below 0.026 m3

2009 and 11.6% for March 2009.

by valve types T10 and T20.

and water meter class.

meter with 20 mm rated diameter and flow of 0.026 m3

**Figure 1.** Structure of the UFR- manufactured by A.R.I. from Jerusalem (Israel) [4] 1 - flow direction, 2 - UFR plug, 3 - UFR spring.

Tests were made on parts of the water distribution pipeline in Jerusalem, Larnaca (Cyprus), on Malta, in Kingston (Tennessee, USA) and in Palermo (Italy). Each testing has been carried out with two water balancing: one with and another without UFR in operation. By compar‐ ing the results of the balancing obtained for the mentioned statuses, the contribution of UFR to measuring water volume by water meter was determined.

Testing was also implemented in Jerusalem from March 2005 in a duration of 14 months (8 months without UFR and 6 months with UFR) on two systems, where the first comprised 120 and the second 360 water meters [4, 6]. The used class B water meters were with the fol‐ lowing characteristics: Qa=0.012 m3 /h, Qmin=0.050 m3 /h and nominal flow Qn=2.5 m3 /h. With the usage of UFR, the measured water volume was higher for 16.0-6.1=9.9% (on the system with 120 water meters) and for 26.0-18.8=7.2% (on the system with 360 water meters).

From October through December 2006, a water supply system with 280, class B and C water meters, age over 1-15 years was tested in Larnaca with weekly balancing [6]. The water vol‐ ume measured with UFR was higher for 19.58-9.66=9.92%.

Three tests were made on a system with 26 households on Malta [7-8]. The class D water meters with rated flow of 1 m3 /h were 5 years old in average. The time interval for water balancing was one week. The quantity of water measured by UFR on water meters was more for 26.7-21.2=5.5%, 28-22.2=5.8% and 18.1-12.1=6% than without the use of this valve.

UFRs were installed in a part of a supply network with 35 water meters in Kingston from June 6 to 10, 2008 [9]. The water meters (aged about 4 years) were calibrated prior to the measuring. During the operation with URF a higher water consumption was measured: 10.4% for July 2008, 9.5% for August 2008, 4.9% for September 2008, 11.9% for October 2008, 7.6% for November 2008, 8.9% for December 2008, 3.9% for January 2009, 8.4% for February 2009 and 11.6% for March 2009.

years old. In joint operation of water meters with URF a higher water volume was meas‐ ured: it was 94% in cases of stagnating water meter propellers, 31.8% for flow rates at the commencement of the propeller rotation (further designated as Qa) and 14.4% for Qmin. The valve's most significant contribution was defined for flow at water meter propeller still‐ stand. Due to the characteristics of water meters installed in the Republic of Serbia, a similar

**Figure 1.** Structure of the UFR- manufactured by A.R.I. from Jerusalem (Israel) [4] 1 - flow direction, 2 - UFR plug, 3 -

Tests were made on parts of the water distribution pipeline in Jerusalem, Larnaca (Cyprus), on Malta, in Kingston (Tennessee, USA) and in Palermo (Italy). Each testing has been carried out with two water balancing: one with and another without UFR in operation. By compar‐ ing the results of the balancing obtained for the mentioned statuses, the contribution of UFR

Testing was also implemented in Jerusalem from March 2005 in a duration of 14 months (8 months without UFR and 6 months with UFR) on two systems, where the first comprised 120 and the second 360 water meters [4, 6]. The used class B water meters were with the fol‐

the usage of UFR, the measured water volume was higher for 16.0-6.1=9.9% (on the system

From October through December 2006, a water supply system with 280, class B and C water meters, age over 1-15 years was tested in Larnaca with weekly balancing [6]. The water vol‐

Three tests were made on a system with 26 households on Malta [7-8]. The class D water

balancing was one week. The quantity of water measured by UFR on water meters was more for 26.7-21.2=5.5%, 28-22.2=5.8% and 18.1-12.1=6% than without the use of this valve.

UFRs were installed in a part of a supply network with 35 water meters in Kingston from June 6 to 10, 2008 [9]. The water meters (aged about 4 years) were calibrated prior to the

/h, Qmin=0.050 m3

with 120 water meters) and for 26.0-18.8=7.2% (on the system with 360 water meters).

/h<Qmin<0.060 m3

/h.

/h and nominal flow Qn=2.5 m3

/h were 5 years old in average. The time interval for water

/h. With

research is necessary for water meters with 0.025 m3

132 Water Supply System Analysis - Selected Topics

to measuring water volume by water meter was determined.

ume measured with UFR was higher for 19.58-9.66=9.92%.

lowing characteristics: Qa=0.012 m3

meters with rated flow of 1 m3

UFR spring.

Two balancing were made on a part of the supply network with 52 water meters in Palermo: from October 24 through November 14, 2008 without UFR and from December 12, 2008 through January 9, 2009 with UFR [10]. The water meters with 15 mm rated diameter were either 11 years old (33, class C) or older (17 of class B and 2 of class A). During the operation with UFR, the measured volume of consumed water was higher for 28.06-18.91=9.15%.

The use of UFR facilitates the measuring of water consumption at flow rates lower than Qmin.

By fulfilling the condition, that the flow of supply network water losses is below 0.026 m3 /h and that water consumption exceeds Qmin, a water supply network for a single household was set up in the Hydraulic Laboratory of the faculty of Civil Engineering in Subotica. The aim of the test was to confirm the contribution of UFR in measuring water volume by water meter with 20 mm rated diameter and flow of 0.026 m3 /h<Qmin<0.060 m3 /h.

ARI from Jerusalem manufactures UFR with 20 mm rated diameter in three types, designed T10, T20 and T30. Thus, conclusions of testing with valve type T30 could also be controlled by valve types T10 and T20.


**Table 1.** Water volume and calibrated time of water meter of 20 mm rated diameter in the function of typical flows and water meter class.

In line with the Measurement Protocol for Water Meters in the Republic of Serbia, a water meter for water consumption in households is qualified for operation with error below the permitted values, i.e. from ±5% (for Qmin) and ±2% (for Qn and Qt ) from the actual water vol‐ ume [11]. During calibration, water meter operation errors are checked for the foreseen wa‐ ter volumes.

Through this water volume and discharge, the time for which the meter is calibrated was calculated.

To eliminate the effects of opening and closing the flow switch to measuring errors during calibration, the standard in force in the Republic of Serbia stipulates the following: "The un‐ certainty introduced into the volume may be considered negligible if the times of motion of the flow switch in each direction are identical within 5% and if this time is less than 1/50 of the total time of the test" [12]. The same recommendations are given by other standards as well [13-14]. Based on that, the following is recommended: "Should there be doubts about whether the operation time of the valve affects the results of the tests, it is recommended that the tests should be made longer, and never under 60 seconds" [15]. That is to say, for neglecting the impact of flow switch manipulation on the water meter's measuring errors the standards offer a solution during the calibration of water meter only.

**Figure 2.** The test rig for water balancing by water maters on water supply system in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica 1-3 - water meters, 4 - UFR, 5-8 - shut-off valve, 9 - storage tank, 10 - outlet pipe of water meter no. 3, 11 - balance with a bucket to measure the quantity of water flown through water meter

Error in Water Meter Measuring Due to Shorter Flow and Consumption Shorter Than the Time...

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135

The elements of water balance in the rig were as follows: the volume of the inflow water (measured by water meter no. 1), legal consumption billed and measured (measured by wa‐ ter meter no. 2) and the total volume of water losses, which occurred due to the water me‐ ter's inaccurate measuring of flow rates lower than Qmin (measured by water meter no. 3).

The operation of the UFR was regulated by shut off valves no. 5, 6 and 7, for example, by

Water volumes flown through water meters no. 1, 2 and 3 were defined by the difference of two water meter readings. By measuring time (with stopwatch) between two readings, flows Q1, Q2 and Q3 were calculated by means of the defined water volume. The weight of the water flown through water meter no. 3 was measured by a bucket (16 litres) on a scale. The volume of the water was calculated by the density of the water measured by scale and

For the test rig for water balancing in a water supply system, new, calibrated multi-jet pro‐ peller water meters with wet mechanism were installed for water temperature of 30°C, and with rated diameter of 20 mm, class B, with the following typical flow rates: Qa<0.01 m3

The used UFR was manufactured by A.R.I. from Jerusalem, with a rated diameter of 20 mm, product type T30. It was installed upstream to water meter no. 3. In line with the manufac‐ turer's recommendation, in order to provide smooth operation of the UFR between water meter no. 3 and shut off valve no. 8, a 6 m long discharge pipe was installed (marked as no.

/h.

/h,

shutting down valves no. 5 and 6, the UFR was set out of operation.

/h and Qn=1.5 m3

no. 3.

measuring cylinder.

10 in the attachment).

/h, Qt

=0.12 m3

Qmin=0.03 m3

Water consumption in a single household is implemented by the use of taps, washing ma‐ chine, dishwasher-machine and shower in the bathroom, likewise the flushing cistern of the toilet and the like. Each consumption is characterised by the opening and closing of flow switch and the duration of water discharge from the pipeline in order to satisfy needs. The duration of consumption in households is shorter than 1 minute in 95% of consumption cas‐ es [16]. The error in measuring consumption by water meter, due to manipulating the flow switch, practically manifests as an error due to the duration of consumption shorter than the time the meter was calibrated for [17].

Owing to this fact, the primary aim of this paper is to define measuring errors of consump‐ tion shorter than 10 (for Qmin), 12.5 (for Qt ) and 4 minutes (for Qn) of class B water meter with 20 mm rated diameter and flow of Qn=1.5 m3 /h, installed in the water supply pipeline of a single household.

Water meter operation error depends on water meter reading accuracy [18]. The further aim of this paper is to define water consumption measuring error in households shorter than the time the meter was calibrated for, in the function of water meter reading accuracy.
