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MAGAZINE "WATER SUPPLY AND WATER SUPPLY" №6 2010

2021-07-15

Improving the quality of measurement and accounting of cold water consumption in the residential sector

Fresh water suitable for domestic use is a depleted resource, therefore, the attitude towards it should be careful, based on rational consumption. One of the factors stimulating the economical use of water is its objective and high-quality accounting in all areas of consumption. This issue is especially acute for the producers of services in the field of water supply - Vodokanals.
Qualitative measurement and accounting of water production and consumption are necessary conditions for the effective development of water utilities.
Statistics show that the largest consumer of water in cities and towns is the population, which accounts for 70÷80% of total consumption. At the same time, the difference between the volume of supplied and the volume of sold (accounted) water is 40÷50%. The main components of this difference are: technological costs associated with the process of preparing and supplying water to the water supply system; losses caused by pipeline ruptures, unauthorized sampling, as well as poor-quality measurements. It is poor-quality measurement that is the main component of all losses, and, above all, in the housing stock - the main consumer of water.

Consider an apartment building fully equipped with apartment cold water meters and having a common house metering unit installed at the inlet of the pipeline supplying cold water to the house. As statistics show, the balance of water consumption in a residential building is always negative and amounts to 25÷45%. The balance is the difference between the total readings of apartment meters throughout the house and the readings of a common house appliance. If we exclude losses caused by infrequent breaks in intra-house networks, and in new houses they are practically absent, the negative value of the water consumption balance of an apartment building - 25÷45% actually determines the losses of Vodokanals caused by poor-quality measurement of apartment water meters, as well as a long period of data collection on water consumption subscribers.
Consider the nature of the imbalance of water consumption in a residential apartment building.


1. An apartment water meter has a so-called sensitivity threshold, which, when installed in a horizontal position, is 15 l / h and in a vertical position - 30 l / h. This is the minimum water consumption that is recorded by the meter. But in reality, in everyday life, there are very often water flows below the sensitivity threshold of an apartment meter, such as leaks in toilet cisterns, taps, etc., which are summed up throughout the house and reach the flow rate recorded by a common house water meter. The use of water meters, in which the sensitivity threshold is as close as possible to zero flow, will minimize losses when measuring water at low flow rates. There are models of wing-type apartment water meters with a sensitivity threshold of less than 4 l / h and a volumetric type with a sensitivity threshold of less than 1 l / h (Sensus type "820" and "620" Qn 1.5 m³ / h).

2. All water meters of the mechanical principle of operation, which include apartment meters, have two ranges of flow rates (loads) - lower and upper. The border of the transition from the upper to the lower range of costs is the so-called transitional flow (Qt). The measurement of the volume of water passed in the lower flow rate range - from the minimum (Qmin) to the transitional (Qt), occurs with a relative measurement error of ± 5%, and in the upper flow range - from the transitional (Qt) to the maximum allowable (Qmax), with an error of ± 2%. Therefore, the use of apartment water meters with a lower transitional flow rate will expand the measurement zone with an error of ± 2%, and shift the interval of the lower flow rate range, which has a measurement error of ± 5%, closer to zero. Accordingly, the minimum flow rate (Qmin) and the sensitivity threshold are shifted to the beginning of the measurement (zero flow rate), which together, of course, improves the measurement accuracy.
These two points are met by water meters in the metrological accuracy class "C".

3. Statistics show that most residential water meters are installed in a vertical position. Let's see how this affects the measurement accuracy. Classical apartment water meters are single-jet impeller type with the axis of rotation of the impeller located perpendicular to the water flow supported by point bearings. Therefore, when the meter is operated in a vertical position or inclined with respect to the horizontal axis of fluid movement, the contact area of ​​the axis of the rotating impeller with the supports increases, which means that friction increases. As a result, the sensitivity of the meter is lost at low flow rates, the measurement accuracy deteriorates, which is one of the significant drawbacks in the design of a classic apartment water meter. There are types of meters, primarily volumetric type, whose metrological characteristics do not depend on the position on the pipeline.

4. Another factor that determines the measurement accuracy is the stability of the instrument's metrological parameters. In some cases, the use of apartment water meters with high initial metrological characteristics can significantly improve the measurement accuracy and reduce the balance in an apartment building to 5%, but only in a short time interval. This short-term effect is caused by a rapid deviation of the metrological parameters of the meter from the factory settings. The stability of the meter depends on a number of factors:

    • device design;
    • quality of production of components;
    • the ability of the materials used to resist the deposition of hardness salts, the so-called "scale", on the surfaces of the elements of the hydraulic chamber of the water meter.

    Of all the variety of systems for the collection and remote transmission of data, the SensusScout system should be singled out, which meets all of the above requirements. It has received practical application in many water utilities and heat supply organizations, which highly appreciated the convenience, simplicity and reliability of its operation.


    A good example of the organization of qualitative measurement and accounting of water consumption in a multi-storey residential building was a pilot project implemented in the city of Ternopil by the IN-Prem enterprise together with KP Ternopolvodokanal. For the implementation of the project, an apartment building was selected, fully equipped with apartment water meters (DN 15 mm, Qn 1.5 m³ / h), in the amount of 27 pieces, installed in a vertical position, and a common building counter DN 40 mm, Qn 10 m³/h. The imbalance of water consumption at home before the implementation of the project for 6 months (November 2008 - April 2009) was 20.9%.


    During the implementation of the project, all meters were replaced with highly sensitive ones, in the metrological accuracy class "C": apartment - type "820 Qn 1.5" DN 15mm with installation in a vertical position, general house - type "620 Qn 3.5" DN 25 mm .

    An autonomous radio data acquisition system SensusScout was deployed at this facility.

    For its organization, all counters were equipped with radio modules (see photo).


    The information from the meters was taken on the last day of the month by the service personnel of the Ternopilvodokanal utility using the Psion portable radio terminal, which has information about the factory numbers of the meters with their location address and readings at the time of the last reading. All data received by the Psion terminal is up-to-date at the time of polling the radio modules. It took about 15-20 minutes to remove information from all the counters in the house. In places that are difficult to reach for the passage of a radio signal, for example, a basement where a common house meter is installed, information was transmitted through another nearby radio module, which acted as a repeater.


    At the request of Ternopilvodokanal, in July 2010, a Scout-Web hub module was installed at this facility, which expanded the capabilities of the SensusScout system - it allowed, in addition to a mobile data transmission system, to have a stationary one, to poll radio modules installed on water meters, at the request of the operator from the office of KP "Ternopilvodokanal". Thus, the need for visits to the site by the Vodokanal personnel was eliminated. The data was collected by the Scout-Web module and transmitted over the network of one of the mobile operators to the control room.


    The result of the pilot project described above showed the following: from November 2009 to April 2010 (six months), the difference between the readings of the general house meter and the total readings of apartment meters was 0.45%. The use of high-precision water meters type "820" made it possible to minimize the existing imbalance of water consumption in the house and obtain the stability of its indicator for more than 6 months. The experiment made it possible to prove the effectiveness of the use of highly sensitive meters type "820", as well as the feasibility of using systems for remote data transmission from meters. The economic effect from the implementation of the project with a fairly small number of subscribers for six months amounted to 376.516 m³. At the same time, it should be noted that a house was chosen for the implementation of the project, which has an imbalance indicator of 20.9%, which is lower than the average for the region and in Ukraine as a whole. As a rule, the imbalance in the housing sector is 40-50%, which means that the efficiency of investments aimed at improving the quality of water consumption measurement and accounting will be several times higher.


    The use of high-precision water meters type "820" made it possible to minimize the existing imbalance of water consumption in the house and obtain the stability of its indicator for more than 6 months.

    Lukash Oleg

    Krasnozhon Iryna

    Equipment Used

    Mechanical water meter 820
    Mechanical water meter 820
    Mechanical water meter 620
    Mechanical water meter 620
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