Reference: EPA- Safe Drinking Water (Fifth Edition)

The secondary pollution of tap water means that tap water is exposed to external pollution during transportation. It may happen when the user’s water-using facility is unqualified, the water tower does not clean regularly, or the pipeline is damaged due to the earthquake or house reconstruction.

1. Information for reservoir and water tower

The reservoir is located inside/outside the house or in the basement to receive tap water from distribution system. And the water tower is installed on the roof or independently elevated outside as a water storage facility. There is no restricted type of storage facility and it should be located somewhere far from potential pollution sources such as septic tank.

2. Regular clean and maintain water facilities(reservoir and water tower)

To insure water quality, people should regularly check and clean water facilities. It is recommended to clean reservoir and water tower at least once half year. Inspect relevant equipments and arrange for professional cleaning services to clean water facilities.

3.Do not pump water directly from the tap water supply pipe

 If the motor is directly pumped, the amount of water in the tap water supply pipe is extracted in a short time. When peak water consumption or water pressure is low, the pressure in the tap water pipe is less than the pressure in the surrounding water. This is the formation of negative pressure. The crack will cause the outside sewage to be sucked into the tap water pipe from the crack, causing serious pollution of the water quality.

4.Equip the effective quantity of reservoir and water tower

In order to avoid the shortage of water supply, people often design oversize water reservoir or water tower. It cause water maintain in the reservoir for a long time, which is a good place for bactrtia to thrive because of insufficient chlorine.

5.Replace water supply pipeline

The quality of the water supply pipe is recommended to comply with the Chinese National Standards (CNS).

6.The water storage tanks are not regularly maintained and cleaned

Cleaning the water storage tower is a very important maintenance work for water equipment.It is recommended to clean at least once every six months to one year.

7.Don’t mix tap water with other water sources

If the tap water in reservoir or water tower connect with other water sources, it will be polluted when flow in the contaminated water.

8.Strengthen reservoir and water tower structure

The manhole cover edge of the reservoir or water tower should be higher than the top of tower. Manholes should be sealed and locked up to keep out contaminated water or suspended materials. Reservoir/water tower air vents, overflow pipes and drain pipes should be installed with insect net to keep out insects and dust causing water pollution.

9.Reservoir and water tower inlet shoule be installed higher than the highest water level

If reservoir and water tower inlet lower than the highest water level, it may be immersed in the water and easily cause siphon effect. At this time, the water in the reservoir/water tower may flows back to the supply pipe, which is likely to cause tap water pollution.

10.Don’t drink immediately after water supply stop

Generally, during the water supply stop, the pipeline inside pressure will be smaller than outside. If the pipeline has old cracks, the contaminated water outside will easily infiltrate, and water is polluted after water regain.