1、Background

As the Ministry of Construction requires water supply companies to read water meters at each household, the one-meter-per-household work is being carried out in full swing among urban water supply companies across the country. This has indeed reduced many old conflicts between users and water supply companies, such as the total sub-meter does not meet the requirements. There are a series of problems such as disputes over water leakage and water bills, as well as sufficient water pressure on the pipe network but low water pressure in users' homes.

However, as the work of one household per meter continues to deepen, many new problems have arisen, such as the determination of the installation location of household meters, winter warmth, meter reading charges, and water meter rotation, among which water meter rotation issues are particularly important.

In the early days, users did not directly deal with water supply companies because they were all metered, and the direction of indoor pipelines and the installation locations of water meters were installed in layers. The distance between meters was large, and the pipeline layout in users' homes was also relatively simple. Most of them had only Consisting of a sink, a washbasin and a toilet, the water meter is less likely to rotate. Therefore, users have never reported water meter rotation problems.

With the continuous improvement of people's living standards, there are more sanitary ware in the home, the pipeline layout is relatively complex, and the water consumption increases. In addition, with the implementation of "one household, one meter", water bills are settled directly between users and water supply companies, and water prices are also changing. Keep rising. Therefore, users have also begun to pay attention to the operation of their water meters, and the problem of water meter rotation has naturally become prominent.

2. Causes of rotation problems

The water meter rotation problem is caused by many factors. This article analyzes the characteristics of the water supply pipeline network and the characteristics of the current water meters themselves. The main reasons are as follows:

2.1. Pressure fluctuation

Since water is a liquid, its physical properties are incompressible under normal circumstances. However, in tap water pipes, when there is considerable pressure in the pipe, the water will show a certain degree of compressibility.

In tap water pipes, pressure fluctuations are inevitable, and most of the water meters we currently use are mechanical meters, which rely on the kinetic energy generated by the flow of water to drive the gears to achieve the purpose of measuring water volume; when not used When there is water, there is a fixed amount of high-pressure water in the pipes connected to both ends of the water meter.

Therefore, when the pressure in the municipal pipe network increases, the volume of tap water in the pipe behind the meter will shrink due to the increase in pressure. At this time, a trace amount of water will pass through the water meter, causing forward rotation; when the pressure decreases, the volume in the pipe behind the meter will be reduced. The compressed water expands due to the reduction in pressure. There will also be a trace amount of water passing through the water meter, but the difference is that it is reversed at this time.

We all know that when a mechanical watch is filled with water, it goes in from the bottom up and out, pushing the gear to rotate forward; when the water is turned upside down, it goes in from the top up and out, pushing the gear to rotate in reverse; the resistance to the water entering at both ends is different, although the two ends The amount of water entering is the same, but the readings reflected on the water meter are very different.

According to statistics, when there is no air in the pipeline, the amount of water produced is very small, about 0.5--1m3/month. Under normal circumstances, users of water volume will not notice this; at the same time, this is also a normal result of the current metering level.

2.2. Air bag

This causes a large amount of rotational water.

The production processes of water supply enterprises are all constructed in the open air. During the production process, a large amount of gas will be dissolved into the water. At the same time, during the construction process, gas will also be brought into the pipelines. If the exhaust valves on the pipelines are not properly set, the gas will be released. It cannot be ruled out very well.

In this way, if there is no water in the home for a long time or the pipe design is unreasonable, air bags will be generated at the highest point or protruding point of the pipes in the home. As we all know, the compressibility of gas is very high. If there are pressure fluctuations on the pipe network, the space in the pipe behind the meter will expand and contract greatly, so the water meter will rotate more.

According to statistics, the amount of water produced ranges from 2-3m3/month to dozens of m3/month.

Therefore, it seems that the rotation phenomenon of most household water meters at present is mainly caused by the air bag in the pipe behind the meter.

2.3. Installation method and installation quality

2.3.1. Since water meters are now delivered to households, most household meters of one unit are concentrated in a box and installed in a pipe well or meter box. Taking into account the protection against cold and frost in winter and the convenience of meter reading, use a water distributor to connect 2 or 6 water meters. The distance between the meters is small, and the straight pipe section left by the water meter is also short. This will also It affects the normal measurement of the water meter and interferes with each other, causing the water meter to rotate.

2.3.2. Installation quality. Pipeline projects are basically buried underground or in walls and are hidden projects. The national pipeline construction specifications stipulate the installation requirements, construction procedures, acceptance standards and precautions for various pipe and pipeline construction. However, During on-site construction, some managers did not construct according to the specifications, causing more or less quality problems in the pipelines.

3. Solution

3.1. Install check valves before/after the meter. Since the rotation of the water meter is caused by pressure fluctuations and water compression, you can consider installing a check valve, which can prevent water from flowing back.

In this way, when the pressure increases, the water is compressed and the water meter rotates forward; when the pressure decreases, the check valve automatically closes and the water meter does not rotate. When the pressure rises again, as long as the pressure is not higher than the pressure in the check valve, the water meter will not rotate again.

The main reason for the water meter's rotation is that the water meter reciprocates multiple times to measure a large amount of water. Installing a check valve can reduce the frequency of the water meter's rotation, which can well solve the problem of water meter rotation caused by pressure fluctuations.

However, due to the high frequency of domestic water use by residents, and the pipeline pressure fluctuations are small most of the time, which are high-frequency fluctuations, the check valve is required to have high sensitivity and high impurity resistance performance.

The check valves currently on the market all have small diameters and large pressure losses, which have caused energy consumption burdens on the water companies. Due to the reduced diameters and increased pressure losses, residential users have small water output in their homes, especially Pipeline end users, so the water department has another task to solve water disputes.

3.2. Judging from the statistical analysis and processing results of user on-site surveys, the main reason for the phenomenon of water meter rotation is that, in addition to leakage of indoor pipes and water appliances, it is mainly caused by unreasonable installation of indoor pipes that cause air bags in indoor pipes. Therefore, in In future work, we should:

3.2.1. During design, the exhaust valve should be reasonably arranged according to the characteristics of the pipeline to eliminate the gas precipitated in the pipeline in a timely manner. When a newly installed pipeline or a newly installed household meter is supplied with water for the first time, the valve should be opened slowly to evacuate the air in the pipeline as much as possible. Reduce the air content in water.

3.2.2. For newly installed household meters, when installing pipes in residents’ homes, the pipes should be laid upward at a certain angle to reduce pipe bends and break points, and the highest point of the pipe should be designed at a frequently used faucet. , Reduce the chance of air bags in indoor pipe networks.

3.2.3. For household meter renovation projects, when the water meter leaves the home, it may cause the direction of water inflow to the user's home to change, causing some dead water pipe sections to appear indoors. This part of the "dead water pipe section" behind the billing water meter may or If the pipe is located at a higher position or is located in a protruding pipe section of the pipeline, it is easy to generate air bags. These pipe sections should be dismantled or modified during construction.

3.2.4. The water meter user has been uninhabited for a long time, and there is a large amount of gas in the pipeline. It is recommended that the user's situation be investigated when the water meter leaves the home. When the water meter is installed and accepted, the valve behind the meter of the unoccupied user's water meter should be closed, and a contract should be signed with the user to explain the reasons when the water meter leaves the home. If you need water in the future, you can open the valve behind the household meter yourself. If you have other water problems, you can call the 24-hour water supply service hotline of the water department.

3.3. From the statistical analysis, it can be seen that the main reason for the rotation of the water meter is caused by gas, so the installation of an exhaust valve can be considered. However, since the exhaust valve has high requirements on installation location, pipeline layout and check valve sensitivity, it will also add a certain workload to the maintenance and management of the pipeline network. Therefore, unless necessary, install as few exhaust valves as possible.

4、Conclusion

There are many reasons for the rotation of water meters, but generally they can be summarized into two:

The first is subjective factors, which are caused subjectively by humans, such as water leakage and original gas collection caused by human responsibility during construction acceptance. This can be improved by strengthening construction management and improving the work level and responsibility of the staff.

The second is objective factors, which are mainly caused by external objective factors such as the characteristics of the water meter itself, the characteristics of the pipeline and the development of technical level. This aspect must be continuously explored and improved in future work to improve.

5. Suggestions

It is recommended that interested persons in the industry develop and design targeted products based on the characteristics of water pipe networks and the complexity of actual installation of residential water and indoor pipes to reduce or eliminate the phenomenon of water meter rotation.