In response to a media report about impurities found in drinking water samples from various districts, the Development Bureau pointed out that the tests mentioned in the report were not conducted in strict compliance with the international standards adopted by Hong Kong’s drinking water testing programme.

The bureau said, as understood, the media organisation had mainly collected samples of impurities from aerators of water taps, commonly known as strainers, and then placed the samples into water for laboratory testing.

It noted that aerators are a kind of filter accessory commonly installed at household water taps and shower heads to help block impurities, hence the presence of impurities in the samples is simply a result of the strainer functioning, and is not abnormal.

In the past, the Water Supplies Department (WSD) had received similar inquiries, and staff members were deployed immediately to conduct onsite inspection.

They also arranged for flushing of consumers’ water meter, reminded them to cleanse the strainers, and checked for any irregularities in water quality. If a water quality issue is suspected, the WSD would collect drinking water samples for testing and notify consumers about the results.

In fact, only a few of such cases required water sample testing in the past three years, and the testing results showed that the water samples complied with Hong Kong Drinking Water Standards (HKDWS).

The bureau stressed that water quality testing must be conducted in accordance with international standards, including taking reference to ISO5667 of the International Organization for Standardization (ISO) for sampling, and referencing Chinese National Standard GB/T 5750 and the American Public Health Association’s in testing methods and procedures.

The samples tested must be drinking water samples, not those collected from strainers as arranged by the relevant media organisation. In other words, the type of samples, methods and procedures will affect the validity and representativeness of the tests.

As mentioned in the report, impurities collected from the strainers include resin, plastic and silicone. The bureau said it may relate to materials peeling off from pipes or fittings of the inside service of the building. These substances are not soluble in water. If they are found, the inside service should be cleansed as soon as possible.

The bureau explained that the drinking water supplied by the WSD undergoes strict treatment and meets HKDWS. However, materials may peel off from public or inside service pipes of buildings due to aging or water pressure, necessitating the installation of strainers at pipes.

Property owners, registered agents and management offices must carry out regular and proper maintenance of building’s inside service, including cleansing sump and rooftop tanks, to maintain good drinking water quality at the consumers’ taps.

To ensure the city’s drinking water quality, the WSD runs a routine drinking water testing programme, randomly collecting water samples from over 28,000 publicly accessible consumers' taps in shopping centres, community facilities, sports venues and government offices, for testing every year.

The sampling rate is based on international standards and the water quality parameters are drawn up in accordance with World Health Organization guidelines.

Moreover, the WSD randomly selects about 670 residential and non-residential water accounts each year to collect drinking water samples at their water taps and test for six metals, namely, antimony, cadmium, chromium, copper, lead and nickel, to ensure HKDWS compliance. The test results are regularly published on the department’s website.

The bureau added that the WSD had requested more detailed information, including sampling locations, for follow-up with the consumer when enquiries were received from the media organisation. It is still awaiting such information.

Citizens may call the WSD’s 24-hour hotline 2824 5000 to enquire about drinking water quality.