Since January, 2021, the China Business Daily news hotline 029-88880000 has received a total of 128 complaints about tap water. The reporter from Huashang Daily interviewed Kuoray, Vice Minister of Production and Operation Department of Xi ‘an Tap Water Co., Ltd., on the issues with the highest mentioned rate among the 128 clues. You may just have questions about these issues.
ask
Why is the water sometimes light yellow and blue when the tap is turned on?
Answer: The light yellow color is caused by the internal corrosion caused by using cast iron, galvanized pipes or faucets for too long, or the secondary water supply facilities are not cleaned in time. Suggestion: If there is no water at home for a long time, drain the dead water in the water pipe before using it, or turn on the tap after getting up in the morning to put tap water before using it.
The blue color is caused by the aging of the toilet check valve in individual users’ homes, and the toilet cleaning spirit (blue) is placed in the water tank. When the water supply pressure is reduced or the water supply pressure is reduced, the water in the toilet water tank is pumped into the pipeline due to the siphon effect. To avoid this situation, the faulty check valve should be replaced or a new toilet without check valve should be used.
ask
Why is tap water sometimes as white as milk?
A: The main reason is that water dissolves into air. When delivering water under pressure, the air will dissolve into the water under the high-speed mixing and pressure of the water pump. When the faucet is turned on, the pressure will be reduced, and the air originally dissolved in the water will be released immediately, forming many dense and tiny bubbles. At this time, you will feel that the flowing water is milky white, but after standing for a few seconds, with the disappearance of the bubbles, the water will become clear. This is a normal physical phenomenon.
ask
Why is there white precipitation after the tap water is boiled? Is the water quality not up to standard?
A: In our daily work, we often meet residents with this question, and we have collected water samples and conducted water quality tests on the spot many times. It can be said that the water quality in Xi ‘an fully meets the national standards.
Generally, there is a certain hardness in natural water, and the existence of scale in boiling water is a normal phenomenon in groundwater supply areas. Because of the high content of calcium and magnesium ions in groundwater, when water is heated, calcium and magnesium ions and bicarbonate existing in the water form white precipitates such as calcium carbonate and magnesium hydroxide which are insoluble in water. Calcium and magnesium ions are essential elements for human body, which are harmless to human health within the scope of national standards, and citizens can rest assured to use water. In the National Hygienic Standard for Drinking Water, the total hardness index is used to characterize the content of calcium and magnesium ions in water, and its limit value is 450mg/L, while the total hardness of urban water supply in Xi ‘an ranges from 80 to 300 mg/L, and the water quality meets the requirements of the National Hygienic Standard for Drinking Water.
ask
Why do some users report that bugs will be picked up in the faucet?
A: Small organisms such as red nematodes are easy to breed in sewers. Sometimes they crawl into the basin along the sewer hose, or climb to the mouth of the faucet along the outer wall of the faucet. The humidity near the faucet is easy to attract small organisms, which will make users have the illusion that bugs are found in tap water. In order to avoid this situation, the vicinity of the faucet should be kept clean and hygienic. In addition, the secondary water supply facilities (water tanks or residential reservoirs) are not cleaned in time or improperly operated during cleaning, and microorganisms are easy to breed.
ask
Can you measure the water quality value with a water measuring pen to illustrate the quality of water?
A: Some distributors of water purification equipment carry a kind of "water quality testing pen" when selling so-called water purification equipment, claiming that they can detect the content of heavy metals in water. If the detection value is greater than 30mg/L, it will exceed the standard. In fact, this "water-measuring pen" is usually a simple TDS (English abbreviation for dissolved total solids) tester. Dissolved total solids is a term used to describe inorganic salts and a small amount of organic substances dissolved in water. The main components are cations such as calcium, magnesium, sodium and potassium, as well as carbonate, bicarbonate, chloride, sulfate and nitrate anions, which do not represent the content of heavy metals in water. The detection of heavy metals requires the use of large-scale detection instruments, and the cost and requirements are high, which is not possible with a simple "water measuring pen".
The national standard limit of total dissolved solids in drinking water is 1000 mg/L. After advanced treatment, most ions in purified water are removed, so the total dissolved solids are lower than tap water, which is also normal, but this does not mean that tap water is unsafe. On the contrary, drinking water with low TDS content for a long time will reduce the intake of trace elements, which is not conducive to human health.
ask
Why do some people say that the tap water just released from the tap has a slight chlorine smell?
A: In order to ensure the safety of microbial indicators of tap water, water supply enterprises should add chlorine for disinfection in the water treatment process according to the requirements of national standards. The national standard requires that the residual chlorine in the factory water is more than 0.3mg/L, and the residual chlorine in the water at the end of the pipe network is more than 0.05 mg/L. Only when the pipe network water keeps a certain amount of residual chlorine can the secondary pollution of tap water be effectively prevented. Therefore, users with sensitive sense of smell can smell a little residual chlorine for the tap water that has just been released. Due to the different length of the pipe network, the residual chlorine content also changes slightly. The residual chlorine in the water supply area near the water plant will be larger, and it will be smaller far away, which is normal as long as it is within the specified range.
ask
Why does tap water turn black after electrolysis? Is the water quality really too bad?
A: Now some people who sell water purification equipment often do similar "small experiments" to mislead residents. They use two disposable cups, one filled with purified water on the market and the other with tap water, and then insert the electrolyzer into two cups at the same time. After a few minutes, it is found that the tap water cup gradually turns black, and a cotton wadding-like precipitate is also produced; However, the pure water cup only changes in light yellow, which shows that tap water is harmful to human body and using their products can ensure the safety of drinking water.
In fact, the main reason for this is the simple electrolyzer, whose anode is an iron bar and the cathode is an aluminum bar. Because tap water, mineral water and other natural water bodies contain minerals and have certain conductivity, when the two poles of the electrolyzer are plugged into tap water and electrified, an electrolytic reaction occurs, and the iron rod as the anode loses electrons to generate divalent or trivalent iron ions, and the hydrogen ions in the water gain electrons at the cathode to generate hydrogen. After electrolysis for a period of time, the ferrous ions of the anode enter the water body, and the ferrous ions in the aqueous solution are light green, and the trivalent iron ions are hydrolyzed to form reddish-brown flocculent precipitates. However, pure water contains almost no ions and basically has no conductivity, so there is no electrolytic reaction, so pure water is clear in the experiment.
The experiment of electrolyzed water can’t be used as the basis for testing the quality of water at all, but only shows that natural water has conductivity, and some conductive mineral ions in natural water are beneficial to human body.
ask
Why do some residents report that there will be vibration and noise in indoor water pipes?
Answer: There are several reasons for this: (1) The pressure reducing valve in the high-rise building is out of order, and the pressure in the water pipe fluctuates. (2) The indirect water pressure in the area is too high, which causes indirect vibration of indoor water pipes. (3) The direction of indoor pipes is unreasonable, and air is accumulated in the water pipes laid on the ceiling or at high positions. (4) The floating ball valve of the multi-storey roof water tank fails, resulting in continuous impact sound. (5) Air accumulates at the end of the pipeline, causing vibration when the water pressure changes.
ask
How to judge whether it is floor heating or water supply pipeline leaking, and how to know whether indoor and outdoor pipelines are leaking?
A: The simple inspection method is to check the water meter regularly, and check whether the water meter moves when all water facilities are closed. If it moves, it means there may be water leakage.
ask
There is no water in the house, what is the rotation of the water meter?
Answer: It may be caused by the small-flow water leakage of sanitary ware in the user’s home, the drainage of overflow valve of water heater or the leakage of pipeline in the home, so it is necessary to find out the reasons carefully and systematically.
Kuoray, deputy director of the production and operation department of Xi ‘an Water Supply Co., Ltd., said that citizens can call the water supply service hotline 965113(24 hours) whenever they encounter difficulties in daily water use. Www.xazls.com, the official website of Xi ‘an Water Supply Co., Ltd., regularly publishes information on the quality of urban water supply every month and accepts social supervision.
Huashang Daily reporter Xiao Lin
Know it
March 22nd this year is the 30th World Water Day, and March 22nd-28th is the 35th China Water Week. The United Nations has determined that the propaganda theme of World Water Day in 2022 is "Ground-water-Making"
the
InvisibleVisible "(cherish groundwater and cherish hidden resources). The propaganda theme of China’s activities to commemorate "World Water Day" and "China Water Week" in 2022 is "Promoting the comprehensive management of groundwater overexploitation and reviving the ecological environment of rivers and lakes".
Source: Huashang. com-Huashang Daily