The 2,500 l/h multi-jet water meters are commonly used for domestic water metering in Israel. New meters are typically installed in new constructions, but in other installations meters are usually refurbished and reinstalled for further use. There is no limit to the number of refurbishments, and the efficiency of this practice is questionable.
The following legislation virtually governs the domestic water metering market in Israel:
- A man shall not supply water unless metered.” (Water Metering Rule (1955)). The water provider must deliver water meters for check up and calibration once in 5 years. (Water Metering Regulation (1988)).
- New meters shall be installed at new construction. (Municipal Regulations).
While the first and the third of these are straightforward, the second regulation is vague. It is impractical to test and calibrate domestic water meters on site. Consequently, the practice has emerged where existing meters are removed and delivered to a laboratory, where they are refurbished and recalibrated. Eventually these meters are reinstalled at another point.
The regulation does not limit the lifespan of an individual meter, nor the number of times a meter can be refurbished and recalibrated. It should be mentioned also that this regulation is not well enforced. Some water utilities have tended to extend the refurbishment and recalibration period to 7 to 8 years and even longer.
Meter refurbishment methods
- The refurbishment involves the cleaning and painting of the meter body as well as other work. Two methods are applied: Refurbishment: The ‘wet parts’, including the impeller and the measuring chamber, are replaced. The measuring unit, including the sealed register, is taken apart and damaged parts are replaced.
- Conversion: The ‘wet parts’ and the measuring unit kit are both replaced with new items.
In 2001 a voluntary standard for meter refurbishment was defined by the Standards Institute of Israel. However, this standard has been applied by only three laboratories. Since refurbishment is not required by legislation, each water provider is free to choose its own policy. Some, who are interested in providing better service, choose to convert the meters, assuming that this method is more effective. Others, looking for a least cost solution, prefer the first option.
In recent years, tough competition in the meter refurbishment market has led to a dramatic price decline and an increase in complaints regarding the level of service, as meter accuracy has also declined. The water metering law in Israel permits the use of Qn 1,500-2,500 l/h meters. The water quality in Israel is particularly hard. Concern over the functioning of water meters in these conditions led to the selection of a Qn = 2,500 l/h multi-jet water meter as the common type used for the domestic sector.
The accuracy survey
A water meter survey was conducted to better assess the current status of the market. The main goal was to evaluate the reduction over time in accuracy of domestic meters and to establish the optimal meter service period.
For the sake of this work, three types of meter were defined: new meters, which were installed for the first time; refurbished meters, which were reinstalled after refurbishment; and converted meters, which were reinstalled after conversion. The meter age refers to the length of time the meter has been installed in the field.
Meters were selected and classified according to ages 1, 2, 4, 6, 8 and 10 years. It was assumed that to achieve a significant statistical sample, 20 to 30 meters of each type and age would be required.
In order to obtain a homogeneous sample meters were selected according to the following criteria:
- From a single manufacturer, Arad Dalia, which controls the local market.
- From a single refurbishment company, which applies the voluntary standard and is considered as a good practice company.
- From the same city or similar water supply area, so that water quality is similar.
In addition the average meter reading volume should be about 20 m3 per month, which is considered the average consumption per flat in apartment blocks. Strict meter replacement, packaging, transportation and storage procedures were also defined in order to avoid damage to the meters during the process. Laboratory tests included the following:
- Test flow rates of 50, 200, 450, 750, 1,000, 1,250, 2,500 and 5,000 l/h.
- Sensitivity test to measure the starting flow of each individual meter.
- Validity test to validate the meter fitness.
The survey was conducted by a steering committee comprising four members, two each from governmental authorities and the water supply companies.
The water demand pattern was determined by installing data loggers on the 1 l/h pulse emitter of water meters. The results (Table 1) show that 97.5% of the demand flows are less than 1,500 l/h. It should be noted that single short demands of volume less than 1 l and leakages at lower flows than the meter starting flow rate affect the demand curve accuracy. The high flows over 2,000 l/h are believed to be erroneous due to synchronisation problems between the meter and the data logger.
The following results compare the performance of new and refurbished meters. The test of converted meters was not completed due to difficulties in locating a sequence of ‘New’ versus ‘Converted’ meters for the full period. The sample size included 146 new and 176 refurbished meters (Table 2).
Validity tests for installed meters are conducted on meters suspected of erroneous functionality. These tests might be initiated by the customer or by the utility itself. The meter is then shipped to a laboratory for an accuracy test. An error curve of ±10% error in the Qmin-Qt range and ±4% between Qt to Qmax is defined and a meter must not violate this error range.
Validity test results for the tested meters are presented in Table 3. Thirty-five percent of the 1-year-old refurbished meters are disqualified. This segment increases to 71% and 57% in years 8 and 10 respectively. New meters average 10%, except for 30% in year 8. A year-by-year comparison clearly indicates the better performance of the new meters.
Average error and standard deviation
Start flows in new meters range between 15 and 20 l/h and are lower at all ages than the refurbished meters’ start flows, which range between 20 and 30 l/h (Table 4).
The weighted error curve, calculated based on the average errors over time and the domestic demand pattern, provides some surprising results (Figure 1). The new meters’ accuracy error is positive, tending to increase moderately in the first 6 years, but by year 8 the error shifts to negative and less than 0.5% in size. The refurbished meter average error is positive throughout the time range, and except for the sixth year, its growth is moderate until it deteriorates in the tenth year.
The standard deviation (SD) error provides another perspective. Comparison between the two meter types shows that for the new meters the SD is lower at all times. In other words, the SD of 10-year-old meters that have not been refurbished is lower than the 1-year-old refurbished meters. This demonstrates that the measurement reliability of the new meters is clearly higher.
The performance indicators of new meters are good and within the required standard limits throughout the test period. This clearly shows that the lifespan of a new meter could be set at 10 years or more.
Refurbished meters show a positive error, which might be beneficial to water suppliers, yet the use of this type of meter should be questioned in the light of the high number – 30% and more – of non-qualified meters and their low measurement accuracy.
These issues have come to the attention of the Israeli authorities and the above-mentioned laws and regulations are now under assessment. A change is expected shortly. Among the key issues in Israel’s water market currently are a national desalination plan, a national plan to improve water quality from other water sources, and the privatisation of the water utilities.
At the same time there is growing interest in technologies such as automated meter reading (AMR), and devices (UFR) that would improve low flow metering. As a result it is possible that the Qn 1,500 l/h meters might replace the current Qn 2,500 l/h meters as the commonly used meters. The use of AMR will improve the metering and billing processes.