Talking about water-saving technology in building water supply and drainage?

In recent years, the urban domestic water consumption in China has increased year by year, while the quality of source water has decreased year by year. This undoubtedly brings a heavy burden to water supply treatment and sewage treatment. So we should make a big fuss about saving water. A drop of water is negligible. But it has been dripping, and the number is considerable. It is estimated that Didi can collect 3.6 kilograms of water in 1 hour;

1 month can collect 2.6 tons of water. This amount of water is enough for a person's life. As for the continuous small water flow, it can collect 17 kg per hour and 12 tons per month; Roaring "running water" can collect 670 kilograms of water per hour and 482 tons of water per month [1]. So there is great potential for water saving. In particular, the consumption of urban domestic water is quite amazing, and most of the process of urban domestic water use is completed in buildings. Therefore, in order to save urban domestic water, we must explore the application of water-saving technology in building water supply and drainage.

Building water saving is a systematic project. In addition to formulating water-saving laws and regulations, strengthening daily management and publicity and education, and using price leverage to promote water-saving work, effective technical measures should be taken to ensure the comprehensive and in-depth development of building water-saving work.

1. Prevent the "invisible" waste of water resources caused by overpressure outflow of water supply system.

We know that due to the expansion of water supply network, the extension of water pipes and the height difference caused by building construction, the method of increasing pressure will be adopted in the initial stage of water supply to ensure that the most unfavorable water supply points can get sufficient water supply, so that a large number of water supply areas will be supplied with high-pressure water. Therefore, the hydrostatic pressure in front of the water supply fittings is greater than the outflow head, and its flow is greater than the rated flow. The part of the flow that exceeds the rated flow does not produce normal use benefits, which is a waste of water resources. Because this kind of water waste is not easy to be perceived and recognized by people, it can be called "invisible" water waste.

Some people have measured and analyzed the overpressure outflow from 67 water distribution points of different types of buildings in a building. According to statistics, 55% of the spiral lifting cast iron faucets (hereinafter referred to as "ordinary faucets") and 6 1% of the water-saving faucets with ceramic cores are in an overpressure state. The maximum flow of the two faucets is about 3 times the rated flow. It can be seen that in the existing buildings in China, the phenomenon of overpressure water outlet in water supply system is common and serious. In order to change this situation, the following measures should be taken.

1. 1 reasonably limit the water pressure at the water distribution point.

The "invisible" waste of water resources caused by overpressure outflow has not attracted enough attention. Although there are some restrictions on the maximum pressure of water supply pipe fittings and household branch pipes in the current Code for Design of Water Supply and Drainage in Buildings and the Draft for Soliciting Opinions on Design of Water Supply and Drainage in Buildings (GBJ 15-2000), this is only to prevent the water supply pipe fittings from being damaged due to excessive pressure. Therefore, the pressure of water supply system should be reasonably limited according to the actual situation of overpressure outflow of building water supply system.

1.2 Take decompression measures.

Reasonable allocation of pressure relief device in water supply system is the technical guarantee to control the water pressure within the limit requirements and reduce the outflow of overpressure.

1.2. 1 pressure reducing valve

The pressure reducing valve is a good pressure reducing device, which is divided into proportional type and direct-acting type. The former determines the decompression ratio according to the area ratio, and the latter can decompress according to the preset pressure. When the water user stops using water, the water pressure in the reducer can also be controlled not to rise, and both dynamic decompression and static decompression can be realized.

1.2.2 pressure relief orifice plate and throttle plug

Compared with the pressure reducing valve, the pressure reducing orifice plate has the advantages of simple system, less investment and convenient management. The practice of some units shows that the water saving effect is quite obvious. For example, after Shanghai Jiaotong University installed an orifice with a diameter of 5 mm on the hot water pipe in the school bathroom, it saved about 43% water. However, the pressure relief orifice can only reduce the dynamic pressure, but not the static pressure. The downstream pressure changes with the upstream pressure and flow rate, which is not stable enough. In addition, the pressure relief orifice is easy to block. In the case of good water quality and stable water supply pressure, [3] can be used. The function, advantages and disadvantages of throttle plug are basically the same as those of pressure relief orifice plate. Suitable for the installation and use of small pipe diameter and its accessories.

1.3 adopts water-saving faucet.

The experiment shows that the flow rate of ceramic valve core water-saving faucet and ordinary faucet is less than that of the latter when fully opened. That is, under the same pressure, the water-saving faucet has a good water-saving effect, and the water-saving amount is between 20% and 30%. Moreover, the higher the static pressure, the greater the water output of ordinary faucets and the greater the water saving of water-saving faucets. Therefore, buildings (especially water distribution points with excessive water pressure) should be equipped with water-saving faucets to reduce waste of water resources. 65438-0999 The Ministry of Construction, the State Economic and Trade Commission, the State Bureau of Technical Supervision and the State Bureau of Building Materials jointly issued the "Notice on Eliminating Backward Products in Residential Construction", requiring new residential buildings in large and medium-sized cities to prohibit the use of spiral lifting cast iron faucets, and actively adopt ceramic-piece sealed faucets that meet the Standards for Ceramic-piece Sealed Faucets and the General Technical Conditions for Faucets. Because the main building of our school was built earlier, the faucet in the bathroom is still an ordinary spiral lifting cast iron faucet. We often see that the faucet is loose and it is difficult to tighten the faucet, which leads to water leakage. In fact, this kind of nozzle still has a lot of waste of "invisible" water caused by overpressure. It should attract the attention of the relevant departments of the school, and start from the long-term interests, switch to new water-saving faucets to reduce unnecessary losses.

2. Reduce the amount of invalid cold water in the hot water system.

With the improvement of people's living standards and the improvement of building functions, building hot water supply has gradually become an indispensable part of building water supply. According to the investigation, most of all kinds of hot water supply systems have serious waste of water resources. For example, after the hot water distribution device in our home is turned on, it often takes a lot of cold water to be used normally. This part of the lost cold water has no use benefit and can be called invalid cold water, that is, wasting water. Cold water is ineffective for many reasons. We should find ways to reduce the discharge of invalid cold water from all aspects of building hot water system. You can also consciously collect this part for flushing hair such as toilets.

2. 1 adopt branch pipe or riser circulation mode.

The circulation mode of hot water system directly determines the existence of invalid cold water and the relative size of cold water quantity. There are three modes of hot water circulation in the current design code for building water supply and drainage in China: main pipe circulation, vertical pipe circulation and branch pipe circulation; At the same time, the hot water supply system is allowed to be small and the use requirements are not high, such as public toilets. , there is no circulating pipeline. A survey shows that the branch pipe circulation mode is the most water-saving, and the vertical pipe circulation mode saves water than the branch pipe circulation mode, but the investment payback period is shorter, which has obvious economic advantages. However, the main circulation mode has no advantage in terms of water saving or project cost recovery. Non-circulating system will produce a lot of ineffective cold water, which does not meet the requirements of water saving and brings inconvenience to people's use. Based on the above analysis and China's national conditions, the main pipe circulation and non-circulation mode should no longer be adopted in the hot water system of new buildings, but the branch pipe circulation or vertical pipe circulation mode should be selected according to the specific conditions of buildings.

2.2 The existing non-circulating timing hot water supply system should be reformed within a time limit.

At present, most public bathrooms in China use non-circulating timed hot water supply system, which discharges a lot of ineffective cold water before bathing every day. Because the pipeline of non-circulating system is simple, the reconstruction project has less investment, quick effect and easy implementation. For example, return pipe is added to the student bathroom hot water main of Beijing Jiaotong University, with a total investment of about 4,000 yuan and annual water saving of about 960 m3. If the water price is calculated according to 3.9 yuan /m3, the annual water fee can be saved by 3774 yuan, and the investment can be recovered in 13 months, which not only can achieve good water-saving effect, but also can obtain good economic benefits.

2.3 Reduce the waste of water caused by temperature regulation.

In order to reduce the waste of water resources caused by temperature regulation, public bathrooms should adopt single-pipe hot water system, and the temperature control device is the key component to control its water temperature. In life, we can find that the existing temperature control device is not sensitive enough, and the bath water is hot and cold. Therefore, we should actively develop single-tube water temperature control equipment with stable and sensitive performance. At present, the mixing modes of cold and hot water in double-pipe hot water system of buildings in China are mostly mixing faucet and double-valve adjustment. Every time the water distribution device is turned on, it needs to be adjusted repeatedly to obtain water with appropriate temperature. Therefore, the hot and cold water mixing faucet with temperature controller should be gradually adopted to quickly obtain hot water that meets the temperature requirements and reduce the waste of water resources caused by too long temperature adjustment time.

3. Prevent waste of water resources caused by secondary pollution.

The occurrence of secondary pollution accident makes the building water supply system unable to work normally, which makes it difficult for users to use water. At the same time, polluted water will be discharged; Cleaning the water supply system also requires a lot of tap water, resulting in a serious waste of water resources. Therefore, it is of great significance to prevent the secondary pollution of building water supply system and save water.

3. 1 variable frequency speed regulating pump is used for water supply in high-rise buildings.

The pressurized water supply mode of pool, pump and high-level water tank is the most widely used water supply mode in high-rise buildings at present. The research shows that the qualified rate of water quality indicators in this water supply system has decreased, about half of which is caused by the pressurized transportation and storage of water. The water in the water storage tank is directly delivered to the user by the water pump, which saves the water tank and reduces the probability of secondary pollution. In some areas of our country, this water supply mode has been clearly adopted under certain circumstances. Shanghai residential design standard stipulates that when the residential design scale is more than 400 households, the variable frequency speed regulating pump will be used for centralized water supply. In other cities, variable frequency speed pumps have also been applied to some extent.

3.2 The life of the new building is set separately from the fire pool.

At present, most high-rise buildings are built together with fire storage tanks, and the storage tanks are too large, and the domestic water reserves are generally less than 20% of the total reserves, and the storage time of domestic water is too long, sometimes as long as 2 ~ 3 days. The research shows that when the water temperature is high in summer, after the water in the water tank is stored for 12 hours, the residual chlorine is zero and the bacteria multiply rapidly. In the monthly fire test, the jointly built pool will also cause waste of fire test. Separating the drinking water pool from the fire water pool can greatly reduce the bacterial pollution of domestic drinking water. Fire test water can be discharged into the fire storage tank without being discharged to the outside. In addition, the total volume of the sub-built water pool will not increase basically, and the cost will not increase too much. It can also optimize the basement design and effectively use the basement area. Therefore, from now on, the living pool and fire pool of new buildings should be encouraged to be set separately.

3.3 Strictly implement the provisions on preventing water pollution in the design code.

The secondary water supply mode of pool, pump and water tank has the advantages of stable and reliable water supply and water pressure, although there are secondary pollution problems. Therefore, it is impossible to completely eliminate this water supply mode, and the provisions in the design code on the selection of pool (tank) materials, pipeline and structure design, and prevention of backflow pollution of pipeline system should be strictly implemented to prevent water pollution caused by improper material selection, design and construction.

3.4 Pool and water tank should be cleaned regularly, and secondary disinfection measures should be strengthened.

In order to ensure the good sanitary condition of the water tank, the health and epidemic prevention department should strengthen the supervision of water quality and tank cleaning, and should appropriately increase the number of tank cleaning. When the water stored in the drinking water pool (tank) cannot be updated within 12 h under the maximum daily water consumption, a disinfection treatment device should be set up. Practice has proved that this has played a very good role in preventing water pollution in high-rise buildings.

3.5 Promote the use of high-quality water supply pipelines

In building water supply, the traditional water supply pipe is galvanized steel pipe, but because galvanized steel pipe is easy to corrode and cause water pollution, some developed countries and regions have clearly stipulated that ordinary galvanized steel pipe is no longer used in domestic water supply network. China's Ministry of Construction and other four ministries and commissions also jointly issued a document, demanding that from June 1 day, 2000, the use of cold galvanized steel pipes should be banned in water supply pipelines of new residential buildings in cities and towns all over the country, and the use of hot galvanized steel pipes should be gradually banned according to local actual conditions, and new types of pipes should be popularized and applied [4]. At present, new types of pipes such as copper pipes, stainless steel pipes, PVC pipes, polybutylene pipes, aluminum-plastic composite pipes and high-density polyethylene pipes can be used to replace galvanized steel pipes. Compared with galvanized steel pipe, plastic pipe has certain advantages in economy. Although copper pipes and stainless steel pipes are expensive, they have long service life and can also be used in hot water systems. Therefore, suitable high-quality water supply pipes should be selected according to the nature of buildings and water supply.

4. Vigorously develop water facilities in buildings.

"Middle waterway". As the name implies, it is neither clean tap water on the waterway nor dirty water in the sewer. Concentrate the washing water and washing water for washing faces, bathing and clothes of residents in an area, and after decontamination, oil removal, filtration, disinfection and sterilization, input them into the reclaimed water pipe network for non-drinking water such as flushing toilets, washing cars, watering lawns and sprinkling roads.

So the middle waterway is also called miscellaneous waterway. Using one cubic meter of water in the middle canal is equivalent to using one cubic meter of clean water less and discharging nearly one cubic meter of sewage less, killing two birds with one stone and saving water by nearly 50%. Therefore, intermediate waterways are widely used in many water-deficient cities in the world.

4. 1 Make full use of high-quality miscellaneous drainage such as washing wastewater.

Most of the existing reclaimed water facilities are built in hotels and universities, and the water source is basically bathroom wastewater. For some small-scale units, the amount of bath wastewater is small, the discharge time is too concentrated, and the reclaimed water facilities can not get stable and sufficient water sources. Washing wastewater has the advantages of large water quantity, uniform use time, relatively good water quality and treatment effect, and should be fully utilized as a renewable water source.

4.2 Formulate and implement new water quality standards for reuse as soon as possible.

At present, the reuse of water in buildings is the water quality standard of domestic miscellaneous water. The requirements for total coliform bacteria in this standard are the same as those in Hygienic Standard for Drinking Water, which is stricter than the reuse water standard in developed countries and the Class III water quality standard applicable to swimming areas in China. This has led to two problems: first, many existing reclaimed water projects simply cannot meet the standards; Second, it is difficult to reach the standard, which increases the investment and treatment cost of the reclaimed water project. Therefore, the appropriate limit value of this index should be established as soon as possible to promote the popularization and popularization of reclaimed water projects.

5. Develop good water-saving habits.

Saving water is not to limit people's use of water, or even to prevent people from using water. But let people use water rationally, efficiently and without wasting. As long as families pay attention to getting rid of bad habits, they can save about 70% water. There are many habits related to wasting water, such as: flushing cigarette butts and breaking garbage with the toilet; In order to receive a glass of cold water, a lot of water was put in vain; Wash potatoes and carrots before peeling, or wash them before choosing vegetables; Intermittent use of water (when opening the door to pick up guests, answering the phone, changing TV channels), with the faucet on; Forgot to turn off the faucet during the water stop; When washing hands, washing face and brushing teeth, let the water flow all the time; Do not check the faucet before going to bed or going out; The equipment leaked and was not repaired in time. As can be seen from the following table, in many places in life, as long as we pay attention, the water saved is very considerable.

5. 1 Leak detection plug flow

It is no joke to "drip into a river" at home. Always check the tap water pipes in your home. In order to prevent a slight delay, don't ignore the leakage of faucet and water pipe connector. If you find water leakage, please ask someone or yourself to repair it in time to block the running water. For the water leakage that can't be repaired for a while, use the master gate to temporarily control the water flow. Although repairing and replacing faucets is a professional job, people with a little common sense can master it as long as they are willing to do it, although according to 1996 statistics, half of American families solve these problems by themselves. However, many families in China are very helpless about this. At present, DIY is advocated internationally, that is, changing the faucet yourself.

5.2 laundry water-saving tips

(1) When the washing machine washes a small amount of clothes, the water level is set too high, and the clothes float around in high water without friction. Instead, it is not clean and wastes water.

(2) Don't wash too little clothes. It is also a water-saving method to concentrate on washing after waiting too much.

(3) If the rinsed water is left to the next batch of washing water, 30-40 liters of clean water can be saved at a time.

5.3 Take a bath to save water

Take a shower with a shower nozzle: (1) Learn to adjust the ratio of hot and cold water. (2) Don't keep the water in the sprinkler open all the time, let alone open it. (3) Try to get wet from head to toe, then wipe the whole body with soap and rinse it for the last time. Don't wash your hair, upper body, lower body and feet alone. (4) Take a bath and concentrate. Take some time. Time is water! Don't be idle, let's chat and wash. Don't have a big water fight with your good friends in the bathroom. (5) Don't take the opportunity of taking a bath to "wash clothes and shoes by the way". Take a bath in the bathtub. Pay attention: don't fill it with water. 1/3- 1/4 pots are enough.

5.4 toilet water saving

(1) If you think the water tank in the bathroom is too big, you can put a sandbag or a coca-cola bottle filled with water in the water tank to reduce the amount of water flushed each time. But be careful not to interfere with the movement of water tank components. (2) The water tank always leaks the most, so always check whether it leaks. (3) Using the collected household wastewater to flush the toilet can serve multiple purposes and save water. (4) Regardless of the size and thickness of the garbage, it should be removed from the garbage passage and cannot be washed away with toilet water.

5.5 One-water multi-purpose

(1) You can wash your feet and then flush the toilet. (2) A vat for collecting waste water should be prepared at home, which can completely guarantee the water needed for flushing the toilet. (3) Rice washing water and noodle cooking water are used to wash dishes and chopsticks, which not only removes oil but also saves water. (4) Raising fish and watering flowers can promote the growth of flowers and trees.

6. Promote the use of water-saving appliances

In addition to developing good water habits, it is very important and effective to use water-saving appliances in household water saving. Some people would rather let themselves go with the flow than change water-saving appliances. In fact, it is not cost-effective to pay so much water for a long time. Therefore, vigorously promoting the use of water-saving appliances is an important means and way to realize building water saving.

6. 1 water saving faucet

6. 1. 1 ceramic valve core water-saving faucet

At present, most segmented faucets use ceramic core faucets. Compared with the common faucet, this faucet can save water by 20% ~ 30%. Compared with other types of water-saving faucets, the price is cheaper [3]. Therefore, this kind of water-saving faucet should be widely used in houses and other buildings. We teach the fifth floor and dormitory to use this faucet.

6. 1.2 delay self-closing faucet

The delayed self-closing faucet automatically closes after a certain period of time to avoid long running water. The water outlet time can be adjusted within a certain range, which is convenient and hygienic and meets the requirements of water saving. Very suitable for washing hands in public places. This kind of faucet is used by our carpenters.

6. 1.3 photoelectric control faucet

Although the delayed self-closing faucet saves water, it is difficult to meet the requirements of different users after the water outlet time is fixed. Photoelectric control faucet can overcome the above shortcomings. For example, the latest infrared automatic hand washing device can automatically check the fixed reflector (such as washbasin) below or in front of the device when it is installed for the first time and adjust its working distance according to the distance of the reflector, thus avoiding the phenomenon that the water flow is unchanged due to obstacles in front of the automatic water feeder in the past. Moreover, this intelligent hand washer can stop water even if you don't wash your hands or feed water under your hands, and it can also flush regularly when you don't use it for a long time.

6.2 Water-saving flushing toilet

6.2. 1 Use a small-volume water tank toilet.

At present, China is promoting the use of 6 L water tank water-saving toilets, and toilets with flushing volume of 4.5 L or even smaller have appeared. However, we should also pay attention to the use of small-volume water tank toilets under the condition of ensuring the normal operation of the drainage system, otherwise it will bring problems such as pipeline blockage and unclean flushing. When the secondary water tank flushes urine, the flushing volume is 4 L (or below); When flushing stool, the flushing volume is 9 L (or less). Two-port and two-gear water tank, which opens the lower drain when defecating and the upper drain when urinating. The left picture shows several forms of two-gear water tank switch. According to the Israeli building code, all new buildings must be equipped with two flush tanks. China should also vigorously promote two-stage water tanks, because in one day, people urinate much more than defecate. Take a family of three as an example. If each person defecates 1 time and urinates 4 times a day and uses the existing 9 L water tank, it needs135 L; The amount of water in a day. Use 6 L water tank and 90 l water a day; Using two-stage water tank, the daily water consumption is 75 L. It can be seen that using 9 L two-stage water tank is more water-saving than using 6 L water tank. It is best to use 6 L two-stage water tank to save water. Another advantage of using two-stage water tank is that it does not need to replace the toilet and reform the drainage pipeline system, so it is especially suitable for upgrading the existing building toilet water tank.

6.2.2 Flush-free urinal

The flush-free urinal introduced by the United States is a waterless and tasteless toilet appliance. In fact, it is only a special "trap" device at one end of the urinal, but it is still very popular because of its good economic, sanitary and water-saving effects.

6.2.3 Photoelectric control urinal

Some public buildings have installed and used photoelectric controlled urinals.

6.2.4 Delay self-closing flushing valve

Based on the pilot working principle, it is directly connected with the water official, which can ensure the need of instant flushing of the toilet when the water supply pressure is high enough. Used to replace water tanks and accessories, it has the characteristics of simple installation, convenient use, sanitation, low price and obvious water saving effect. This kind of washing machine is used by our carpenters.

6.3 Install various forms of water-saving appliances in the hot water system.

For example, installing a flow-limiting orifice in public toilets; Install a pressure balancing device between the cold water and hot water inlets; Install and use low-flow shower heads, inflatable hot water faucets and constant-temperature mixed hot and cold water faucets.

6.4 Further develop various forms of water-saving appliances.

6.4. 1 Develop faucets with different water output.

Some countries stipulate that faucets with different water output should be used in different places. For example, Singapore stipulates that the water consumption for washing dishes is 6 L/min and that for shower is 9 L/min. Taiwan Province Province, China, introduced a special faucet for hand washing, with an output of only 1 L/min. However, the rated flow of various faucets in China is mostly 0.2 L/s, that is, 12 L/min, which is obviously too large. Therefore, it is necessary to reasonably formulate the rated flow of various faucets and gradually install faucets with different water output in different places.

6.4.2 Vacuum water-saving technology

In order to ensure the flushing effect of sanitary ware and sewer, vacuum technology can be applied to drainage engineering, with air replacing most of the water, and relying on the high-speed gas-water mixture generated by vacuum negative pressure, the sewage and dirt in sanitary ware can be quickly flushed and sucked clean, so as to save water and discharge dirty air. A complete vacuum drainage system includes: sanitary ware with vacuum valve and special water absorption device, sealed pipeline, vacuum collection container, vacuum pump, control equipment and pipeline, etc. The vacuum pump generates a negative pressure of 40 ~ 50 kPa in the drainage pipeline, sucks the sewage into the collection container, and then the collected sewage is discharged into the municipal sewer by the sewage pump. All kinds of buildings adopt vacuum technology, saving more than 40% water on average. If used in office buildings, the water saving rate can exceed 70%.

6.4.3 Develop water tanks with hand washing taps.

In Japan, many families use water tanks with hand-washing faucets, and all the wastewater generated by hand-washing flows into the water tanks and is reused for flushing toilets. If the water tank needs water, you can turn on the tap and drain it directly. Using this flushing water tank can not only save water, but also reduce the cost of the water tank itself. At present, this kind of water tank has been sold in China.

7. Reasonable setting and use of water meters

7. 1 Improve the metering accuracy of water meters

In the investigation, it is found that the accuracy of water meter measurement is poor due to the problems of type selection and water meter itself. If the model of water meter in some buildings is too large and the water consumption is low, the pointer of the water meter basically does not move. According to the statistics of relevant departments and our research group on the measurement results of water meters, about 40% of water can't meet the precision requirement of 4%. The accuracy of water meter measurement is not only related to the problems of enterprises, but also to the evaluation and countermeasures of leakage control. Therefore, effective measures should be taken to improve the accuracy of water meter measurement.

7. 1. 1 Install the water meter in strict accordance with the specification requirements.

No matter what kind of building, water meters should be selected according to the requirements of Code for Design of Water Supply and Drainage in Buildings to prevent excessive water leakage. The construction unit shall install water meters in strict accordance with the installation requirements of cold water meters and other specifications.

7. 1.2 filter is installed in front of the water meter.

One of the main reasons that affect the accuracy of water meter measurement is the influence of water quality of pipe network, which is mainly manifested in that impurities in water block some water inlet holes of water meter filter screen, resulting in inaccurate water meter measurement. Installing a filter in front of the water meter can solve this problem and reduce the wear of the water meter. In foreign countries, a large number of filters are used before valves, water meters and water appliances in water supply systems, and they are cleaned regularly. However, in China, the effectiveness of filters has not attracted enough attention, and they are only used in a few occasions. Therefore, we should speed up the development of filters and apply them to buildings as soon as possible.

7. 1.3 Limited service life

According to the relevant provisions of the Verification Regulation of Measuring Instruments for Compulsory Verification (Trial) issued by the State Bureau of Technical Supervision, household water meters are only subject to compulsory verification for the first time, and they are used within a limited time and replaced when due. However, due to the lack of effective measures to implement the above provisions, most water meters under construction are used indefinitely. Due to the mechanical wear of the parts of the water meter itself, the longer the service life of the water meter, the lower the accuracy. Singapore's experience is that 15 mm water meters, 85% of the water meters can keep the accuracy within 3% once every seven years, and large water meters adopt a meter changing cycle of 2-4 years according to the situation. Therefore, all localities should, in accordance with national requirements, make restrictive provisions on the service life of water meters and force them to be replaced when they expire. Service life: 15 ~ 20 mm water meter shall not exceed 6 years, and 25 ~ 50 mm water meter shall not exceed 4 years. In addition, in order to ensure the accuracy of the water meter, the property management department and the water supply company should regularly check the water meter, find the problems in the use of the water meter in time, and maintain a good working environment of the water meter.

7.2 develop IC card water meter and remote water meter

At present, household water meters are widely installed in residents' homes, which brings inconvenience to residents' lives. At the same time, when residents decorate indoors, they often cover (hide) the originally installed water meters, which brings great difficulties to the maintenance and management of water meters and meters. In recent years, China's residential design began to set the water meter relatively centrally or uniformly on the first floor (or equipment floor), or set the water meter in the tube well. These designs will increase the water supply pipeline and cost, and at the same time increase the construction difficulty and the inconvenience for residents to check the water meter. In economically developed countries and regions, IC card water meters and remote water meters have developed rapidly. In a residential area in Tokyo, meter reading is centralized by computer through telephone line, and it only takes 2 s[3] for each household to look up the meter [3]. It can be seen that the application technology of water meter in China should develop to IC card water meter and remote water meter system.

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The key to water saving is not building water saving technology, but people's awareness of water saving and people's habits of water use. According to the survey, this concept has not really been effectively established. Therefore, it is imperative to advocate people to regard fresh water resources as rare resources, save their use and call on the whole people to save water. As long as one measure or several measures are used at the same time, the water-saving effect will be remarkable. Under the premise of following the ecological law, economic law and social development law, within the carrying capacity of water resources and water environment, under the guidance of water demand management theory, under the guidance of a sound legal system, and under the guidance of the government, comprehensive use of administrative, legal, management, economic, publicity and education, science and technology and other means and measures can not only achieve unified management and scientific allocation, but also alleviate the contradiction between supply and demand of urban water to a certain extent, solve the problem of water shortage during peak hours and reduce sewage discharge.

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