Is the tap water at my home potable?

• The quality of water treated in WSD treatment works is as good as that of many well-developed countries and regions. You can drink tap water without boiling on condition that the management of your building is done properly.

• When water is delivered to consumers' taps via inside plumbing, the quality may not be the same as the quality of water produced by the treatment works. It is because unlined galvanized pipes were widely used in Hong Kong in the past. These pipes began to corrode after being in use for several years. Discoloured water results after water has been stagnant inside the pipe for a certain period of time.

• As far as is known, we suffer no harmful effects from drinking water with traces of dissolved iron. In fact, the average person's daily intake of iron from consumption of food far exceeds that from drinking such water. Under normal circumstances, this aesthetic problem can usually be overcome by running the tap for a few seconds. For the more serious cases, replacement of the water pipes may be necessary.

• Since 23 December 1995, the use of unlined galvanized pipes has been prohibited. To avoid corrosion of pipes, other pipe materials such as lined galvanized steel pipes, copper pipes, stainless steel pipes and polyethylene pipes are recommended.

• The maintenance of water storage tanks is also very important. Therefore, you should monitor the management office of your building to make sure that they regularly clean the water storage tanks and maintain the water supply system in good condition. If you have doubts about the cleanliness of the supply system in your building, you should consider boiling water for drinking.

• Villagers relying on wells or streams for drinking should always boil the water for drinking.

Is Hong Kong's treated water safe for consumption?

• Hong Kong's water is safe and the risk of getting cancer from drinking water is almost zero.

• Average chloroform (a substance considered as possibly carcinogenic to human) levels in our water have remained less than 50 g/litre for a long time, which is far lower than the WHO guideline value of 200 g/litre.

• In our daily life, the chance of contact with carcinogenic substances through other channels is greater than that of drinking water. According to scientific research, the chance of getting cancer is less than 1 in 100 000 if you drink 2 litres of water containing 200 g/litre chloroform every day for 70 years continuously.

Why does the tap water contain a smell of chlorine?

• As the majority of Hong Kong people are living in high-rise buildings, it may take a long time for the final water from treatment works to go through the roof tanks before supplying to the consumers. A small amount of residual chlorine is maintained in the water to keep it free from bacterial infection during its journey in the distribution system. This minimal amount of chlorine will disappear if the water is boiled.

Why are sediments always found in my electric kettle?

• In Hong Kong, the treated water which is soft in nature is left with a small amount of minerals even it is visually clear. If you do not wash the electric kettle after frequent uses, sometimes it is observed that sediments of minerals will be left and accumulated in your electric kettle.

• Minerals left in your kettle are mainly calcium salts, trace amounts of which will not adversely affect the water quality or our health. This phenomenon is more common in other countries using hard water.

• You can simply use lemon juice to remove the minerals that have accumulated in your electric kettle.

Is it necessary to install a domestic water filter (including that incorporated in a drinking fountain or other similar water using apparatus)?

• Hong Kong enjoys one of the safest water supplies in the world. The quality of the water supplied by the Water Supplies Department (WSD) up to customers' building/lot boundaries conforms to the Guidelines for Drinking-water Quality recommended by the World Health Organization and is stringently monitored through extensive sampling at treatment works, distribution networks and customers' taps. WSD does not recommend the installation of any domestic water filters because they may become ideal breeding ground for bacterial growths and give rise to health hazards if they are not properly maintained.

• Provisions in Waterworks Regulations 24 stipulates that water using apparatus, such as water filters, shall not be installed or used without permission of WSD, who may require that such water using apparatus shall not be directly connected to mains water supply systems to avoid the possibility of contamination of mains water supply systems. While we have no plan to demand customers to remove the faucet or countertop type water filters installed, we would remind customers of the need for proper maintenance of the water tanks and water pipes in their buildings so as to maintain the water quality and to reduce the possibility of pollution arising from the use of water filters. In fact, we have been actively promoting the Quality Water Recognition Scheme for Buildings. Under the scheme, buildings with plumbing systems properly maintained and water sample test results complying with our water quality indicators will be awarded certificates to give recognition to their efforts. The tap water of these buildings is fit for direct consumption. Since its implementation in 2002, the scheme has received favourable and supportive responses. A substantial number of buildings in Hong Kong have already been awarded such a certificate.

• As stated above, there is no need for installation of filters if your premises' fresh water plumbing system is properly maintained. However, if for some reasons that you still opt to install a water filter, you shall ensure - besides proper maintenance of the filter - that provisions will be made to prevent contaminated water backflowing from the filter to the communal water supply system in the event of sudden pressure reversal due to unforeseen breakdown of the communal supply system or the government mains supply system.

• If the water supply to your premises is provided by a dedicated water main from a roof tank (see Fig.1), you may install a minor type of domestic filter - faucet filter (see Fig. 2) or countertop filter (see Fig. 3) - on your own provided that there is no stop valve downstream of the filter. In general, if your water meter is located at the roof of your building, the chance is high that the water supply to your premises is provided by a dedicated water main. You should make an enquiry to your building's management agent or consult a licensed plumber if you are not certain whether you have a dedicated water supply from a roof tank.

• If the water supply to your premises is provided from a roof tank but not by a dedicated water main (see Fig. 4), you may engage a licensed plumber to install a minor type of domestic filter - faucet filter or countertop filter - without prior approval from WSD on the condition that a non-return valve will be provided either within the filter or upstream of the filter (there being no branch pipe in between the valve and the filter in the latter case). There shall be no stop valve downstream of the filter.

• For circumstances other than above (for instance premises on direct supply, (see Fig. 5), customers shall employ licensed plumbers to install filters for them. The licensed plumbers shall submit for WSD's approval the details proposed for preventing backflow of water from the filters to communal supply systems or the government mains supply systems. WSD may give permission for a domestic in-line filter (see Fig. 6) of Point-of-use type (including in-line filter used in drinking fountain) under either direct or indirect supply situation if a single check valve or no less effective backflow prevention device is provided upstream of the filter and there is no branch pipe in between the device and the filter. However, off-tank supply provisions are required for all Point-of-entry type filters.

• Please note that customers shall be responsible for the quality of water passed through their filters and proper maintenance of the filters. WSD does not have a list of acceptable filters or require any test results of the filters before installation, i.e. "general acceptance" is not required and will not be given.