The Development Bureau on Sunday said a media report about impurities found in drinking water in various districts was based on inadequate testing, as the samples had been taken from water tap strainers.

In a statement, the Development Bureau said 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.

A spokesman said the media organisation had mainly collected samples of impurities from water tap strainers, and then placed them into water for laboratory testing. He said the report mentioned resin, plastic, and silicone in the strainers which may be due to material peeling off from pipes or fittings inside the building.

"Drinking water supplied by the Water Supplies Department undergoes strict treatment and meets Hong Kong drinking water standards. However, materials may peel off from public or inside service pipes of buildings due to ageing or water pressure, necessitating the installation of strainers at pipes," he said.

He said such substances are not soluble in water and, if they are found, cleansing should take place. The spokesman added that impurities in strainers were not abnormal.

"If there was a suspected water quality issue, the Water Supplies Department 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 testing results showed that the water samples complied with Hong Kong drinking water standards," he said.

The statement said the Water Supplies Department runs a drinking water testing programme each year which does meet international standards.