**2. The description of the test rig and the tested statuses**

In 2010 and 2011, a test rig was set up in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica with two-outlets and consumption and water losses were measured by water meters no. 2 and 3.

Error in Water Meter Measuring Due to Shorter Flow and Consumption Shorter Than the Time... http://dx.doi.org/10.5772/51046 135

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

ume [11]. During calibration, water meter operation errors are checked for the foreseen wa‐

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

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

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

Owing to this fact, the primary aim of this paper is to define measuring errors of consump‐

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

In 2010 and 2011, a test rig was set up in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica with two-outlets and consumption and water losses were measured

time the meter was calibrated for, in the function of water meter reading accuracy.

**2. The description of the test rig and the tested statuses**

) and 4 minutes (for Qn) of class B water meter with

/h, installed in the water supply pipeline of a

) from the actual water vol‐

permitted values, i.e. from ±5% (for Qmin) and ±2% (for Qn and Qt

the standards offer a solution during the calibration of water meter only.

time the meter was calibrated for [17].

single household.

by water meters no. 2 and 3.

tion shorter than 10 (for Qmin), 12.5 (for Qt

20 mm rated diameter and flow of Qn=1.5 m3

ter volumes.

134 Water Supply System Analysis - Selected Topics

calculated.

**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 no. 3.

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

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 measuring cylinder.

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 /h, Qmin=0.03 m3 /h, Qt =0.12 m3 /h and Qn=1.5 m3 /h.

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. 10 in the attachment).

Water was brought from the reservoir to the rig by gravitation. According to the pressure and flow rate, the rig complied with a single household water supply pipeline.

Two statuses were tested: a) Q2=0 and b) Qmin≤Q2≤Qn.

Under the Regulations on the Measurement Protocol for Water Meters of the Republic of Serbia, measuring error of a water meter is defined as:

$$\mathbf{G} = \frac{100 \text{(Vi} - \text{Vc)}}{\text{Vc}} \text{(\text{\textdegree\prime})} \text{ \textdegree \text{\textdegree} } \tag{1}$$

termined values for Q3<Qmin. Since flow rate Q3 has always been lower than Qmin, there is no

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

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

137

During accuracy measurements, water meter readings were 2.5 centilitres. Measurement ac‐

Error in water meter measuring due to consumption shorter than the time the meter was calibrated for: a water supply pipeline was set up in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica (in 2011 and 2012), gravitationally supplied from a tank with constant water level, i.e. for 16.25 m higher than the level of the water meter axis. Ac‐ cording to both water flow and the water supply pipeline characteristics, the water supply

**Figure 3.** Part of the water supply pipeline downstream from the water meter (1) in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica. 2 - stop valve, 3 - vessel with scale for measuring water quantity flown through

A stop valve for starting and stopping water flow was installed at 2.8 m downstream from

the water meter, 4 - stop-watch, 5 - measuring cylinder and thermometer, 6 - manometer.

the water meter.

During calibration, the reading accuracy of the water meter was 1 decilitre.

permitted balancing error limit for the tested statuses.

curacy of water quantity in the vessel was 0.005 kg.

pipeline corresponds to the one of a single household.

where:

Vi - water volume flown through the water meter, registered on the meter's counter, and

Vc - water volume flown through the water meter, measured in the bucket on the scale.

The errors changes in the operation of the water meter for status Q2=0 were tested for flow rates Q3<0.026 m3 /h for two cases: without UFR and with UFR in operation at water meter no. 3. Applying the criterion, that the error in the water meter's operation is lower than

$$\mathbf{G} \preceq \mathbf{G}\_{\text{av}} \pm \sigma \text{ (\%)}\tag{2}$$

where:

Gav - is the mean error of the water meter in case of steady flow, and

σ - is the standard deviation of the water meter error in steady state flow,

the time needed for getting steady flow, tst, was defined.

After the time required for establishing steady flow tst was determined, the error in water balancing for status Qmin≤Q2≤Qn and flow rate Q3 was investigated by the rig:

$$\mathbf{G}\_{\rm b} = \frac{100(\mathbf{V}\_2 + \mathbf{V}\_3 - \mathbf{V}\_1)}{\mathbf{V}\_1} \text{(\%)}\tag{3}$$

where:

V1=Q1\*tst - water volume at intake,

V2+V3=Q2\*tst+Q3\*tst - water volume at outlet, and

tst - time for establishing steady flow at water meter no. 3.

The error in balancing was checked for four values of flow rate Q2 - for two flow rates when Qmin≤Q2≤Q<sup>t</sup> and for two flow rates when Qt ≤Q2≤Qn. The series comprised of 1 to 30 measure‐ ments.

Errors in balancing are caused by errors in operation of water meters for measuring water volume: up to ±5% for Qmin≤(Q1 and Q2)≤Q<sup>t</sup> and up to ±2% for Q<sup>t</sup> ≤(Q1 and Q2)≤Qn, and unde‐ termined values for Q3<Qmin. Since flow rate Q3 has always been lower than Qmin, there is no permitted balancing error limit for the tested statuses.

Water was brought from the reservoir to the rig by gravitation. According to the pressure

Under the Regulations on the Measurement Protocol for Water Meters of the Republic of

Vc (*%*) (1)

G≤Gav ± σ (%) (2)

(*%*) (3)

≤Q2≤Qn. The series comprised of 1 to 30 measure‐

≤(Q1 and Q2)≤Qn, and unde‐

and flow rate, the rig complied with a single household water supply pipeline.

G= 100(Vi−Vc)

Vi - water volume flown through the water meter, registered on the meter's counter, and Vc - water volume flown through the water meter, measured in the bucket on the scale.

no. 3. Applying the criterion, that the error in the water meter's operation is lower than

Gav - is the mean error of the water meter in case of steady flow, and

Gb =

the time needed for getting steady flow, tst, was defined.

σ - is the standard deviation of the water meter error in steady state flow,

balancing for status Qmin≤Q2≤Qn and flow rate Q3 was investigated by the rig:

The errors changes in the operation of the water meter for status Q2=0 were tested for flow

After the time required for establishing steady flow tst was determined, the error in water

The error in balancing was checked for four values of flow rate Q2 - for two flow rates when

Errors in balancing are caused by errors in operation of water meters for measuring water

100(V2+ V3 - V1) V1

/h for two cases: without UFR and with UFR in operation at water meter

Two statuses were tested: a) Q2=0 and b) Qmin≤Q2≤Qn.

136 Water Supply System Analysis - Selected Topics

Serbia, measuring error of a water meter is defined as:

where:

where:

where:

ments.

V1=Q1\*tst - water volume at intake,

V2+V3=Q2\*tst+Q3\*tst - water volume at outlet, and

Qmin≤Q2≤Q<sup>t</sup> and for two flow rates when Qt

tst - time for establishing steady flow at water meter no. 3.

volume: up to ±5% for Qmin≤(Q1 and Q2)≤Q<sup>t</sup> and up to ±2% for Q<sup>t</sup>

rates Q3<0.026 m3

During accuracy measurements, water meter readings were 2.5 centilitres. Measurement ac‐ curacy of water quantity in the vessel was 0.005 kg.

Error in water meter measuring due to consumption shorter than the time the meter was calibrated for: a water supply pipeline was set up in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica (in 2011 and 2012), gravitationally supplied from a tank with constant water level, i.e. for 16.25 m higher than the level of the water meter axis. Ac‐ cording to both water flow and the water supply pipeline characteristics, the water supply pipeline corresponds to the one of a single household.

**Figure 3.** Part of the water supply pipeline downstream from the water meter (1) in the Hydraulic Laboratory of the Faculty of Civil Engineering in Subotica. 2 - stop valve, 3 - vessel with scale for measuring water quantity flown through the water meter, 4 - stop-watch, 5 - measuring cylinder and thermometer, 6 - manometer.

During calibration, the reading accuracy of the water meter was 1 decilitre.

A stop valve for starting and stopping water flow was installed at 2.8 m downstream from the water meter.

Water volume flown through the water meter was defined by:


By measuring time (with stop-watch) between two readings, through the defined water vol‐ ume in the vessel, the water flow rate Q was calculated.

With the criterion described by equation (2), steady state flow stabilisation time, tst was de‐

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

0 5 10 15 20 25 30 **Q3 (l/h)**

> **Q3 tst (min.) l/h without UFR** 25.5 15 19.6 13 12.7 16 7.1 22 5.2 90 3 135 1.3 210 **Q3 tst (min.) l/h with UFR** 24.4 10 18.7 13 12.4 16 6.7 28 5 12 2.8 75 1.3 55

**Figure 5.** Stabilisation time of water flow in the installation tst in the function of flow Q3.

**Table 2.** Stabilisation time of water flow in the installation tst in the function of flow Q3.

without UFR with UFR

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

139

fined:

0

50

100

**tst (min)** 150

200

250

During accuracy measurements, water meter readings were as follows: 2.5 centilitres, 1 deci‐ litre and 1 litre. Measurement accuracy of water quantity in the vessel was 0.005 kg (for Qmin), 0.01 kg (for Qt ) and 0.1 kg (for Qn).

Error changes in the operation of the water meter described by equation (1), were tested by applying two method by stopping the water meter: according to the valid Protocol of the Republic of Serbia, the status on the water meter and the scale was read prior and after measuring at water meter propeller in stillstand [12].
