Is tap water drinkable after a rainstorm? What should we do?

In the hot summer, thunderstorms and rainstorms are frequent. Many residents found that the tap water in their homes turned yellow and turbid after the rainstorm. There are also messages on the Internet calling on people not to drink tap water after the rainstorm. So, why does the tap water become turbid after the rainstorm? Can we still drink it?

Generally speaking, except for some areas (rural areas, etc.) that directly use well water or groundwater as domestic water, tap water in other places basically comes from water plants. Water plants collect water from nature, and then go through a series of treatments and purifications before delivering it to every household. The water source used by water plants is called "raw water", which contains various impurities. To ensure the quality of tap water, water plants purify the raw water, which mainly includes four steps: mixing, sedimentation, filtration, and disinfection. After these four steps, the water plant delivers tap water to various regions through pipelines.

During heavy rains, the organic matter, inorganic matter, silt, and garbage in the raw water will increase greatly, making it more difficult for the water plant to draw and purify water. The water plant will increase the amount of coagulants and disinfectants used according to the changes in water quality to ensure that the quality of tap water meets the requirements of the "Sanitary Standards for Drinking Water". Therefore, even after a heavy rain, the tap water purified by the water plant is relatively safe.

So, why does the tap water in residents' homes turn yellow and turbid after a heavy rain?

As mentioned above, even if the turbidity of the raw water is high, it will meet the water quality requirements after being treated by the water plant. However, a large number of pipelines are needed to transport the tap water from the water plant to each household. The yellow and turbid tap water in some residents' homes is likely due to problems with the tap water pipeline. There was once a water pollution accident reported due to the rupture of an old tap water pipeline. The tap water in the residents' homes had a strange smell and was turbid. After inspection, it was found that the water from the factory met the requirements. The source of the pollution was the ruptured tap water pipeline. Sewage flowed in through the cracks in the pipeline, thereby polluting the residents' domestic water[1]. The pipelines in many cities have been used for a long time, and some of them may have rusted and bacterial growth. The water supply pipelines and high-rise water towers in some communities are poorly sealed due to their age and are easily polluted by rainwater.

If we find that the water in our homes becomes turbid after a heavy rain, especially in some old residential areas, the reason for the turbid water is probably that there is a problem with the pipes. Do not drink the tap water at this time. You should promptly inform the property or community administrator to check the tap water pipes in the community. Domestic water affects all aspects of our lives and must be taken seriously.

In addition, the turbidity of raw water increases after heavy rain, and the purification process of the water plant may require the addition of chemical agents such as flocculation disinfection. The water that meets the standards may still contain low concentrations of residual chlorine and flocculants, and long-term drinking may also affect our health. In summary, it makes sense that tap water after heavy rain cannot be drunk, but it also depends on the region. The tap water in some communities with intact and closed pipes and water towers is relatively safe. We can also install a water purifier at home or prepare some purified water to add a guarantee to our health.

References:

1. Wang Debin, Wang Lingling: A water pollution accident caused by the rupture of an old water pipe. Journal of Environment and Health, 2002, 19(005):373-373.