**5. Conclusion**

According to pressure and water flow rate, the test rig in the Hydraulic Laboratory of the Faculty of Civil Engineering Subotica presented a case of a single household water pipeline. The water meters are produced by Potiski vodovodi Ltd. from Horgos with rated diameter of 20 mm, class B, and the following flow rate characteristics: the flow at starting the water meter propeller (Qa) is between 0.0052 and 0.0067 m3 /h, Qmin=0.03 m3 /h, Qt =0.12 m3 /h and Qn=1.5 m3 /h. Upstream from water meter no. 3 an UFR was installed, manufactured by A.R.I. from Jerusalem, with rated diameter of 20 mm, product type T30.

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

According to the measurement results, the most significant contribution of the UFR in meas‐ uring water volume by a water meter of a single household takes place at water losses by flow rate Qa, prior to starting the water meter propeller:

a) 70.57% at flow rates Q2=0 and Q3=0.005-0.0052 m3 /h, and

b) 15.7% at flow rates Q2=0.03-0.0385 m3 /h and Q3=0.0049-0.0053 m3 /h.

The effects of UFR types T10 and T20 manufactured by ARI from Jerusalem on water meas‐ uring accuracy are less than that of type T30.

For calibration discharges, foreseen by the Protocol, through the testing of class B flow meter with 20 mm rated diameter and discharge of Qn=1,5 m3 /h, it has been established, that:


**•** to provide that measuring errors of calibrated flows be lower than the permitted ones, the minimum time for measuring these flows is 5 minutes (for water meter reading accuracy of 2.5 centilitres), 9 minutes (for water meter reading accuracy of 1 decilitre), or 60 mi‐ nutes (for water meter reading accuracy of 1 litre).

Since it concerns 95% of water consumption measurement, such testings are necessary for all types of water meters used in the supply networks of this country.
