The Government’s task force investigating the cause of excessive lead in drinking water in public rental housing estates released its preliminary findings today.
It was found that leaded solder joints were the cause of the excessive lead in drinking water in Kai Ching Estate and Kwai Luen Estate Phase 2.
Speaking at a press conference today, task force chairman Wong Chung-leung said the group held seven meetings in two months and visited the two estates. Over 100 components, including 44 copper pipes, 28 valves, three meters, 12 taps and 47 solder joints were dismantled.
The task force conducted leaching tests, elemental analyses of various components, mathematic modelling and lead isotopic analysis on the components.
The results indicated that copper alloy valves, taps and solder joints of copper pipes with diameters below 76mm dismantled from the water supply chain of Hong Ching House in Kai Ching Estate leached lead, with solder joints found to be leaching the highest amount of lead, with the lead content reaching 41%, 585 times the British Standard of 0.07%.
It was also found that copper alloy fittings also leached lead but did not result in excessive lead in water.
The task force also examined the leaching rate of three other heavy metals - chromium, cadmium and nickel - in all the components dismantled from the water supply chains.
Some valves and taps did not comply with the British Standard for lead content, but leach tests revealed that it did not contribute to excessive lead in the water.
To prevent future occurrence of similar incidents, the task force recommended that site inspection and testing during construction of plumbing works should be enhanced to prevent the use of leaded solder and non-conforming pipes and fittings.
Regular field inspections by qualified experts, tests of soldering joints during construction, and random sampling and testing of soldering materials should be carried out.
It also suggested the Housing Authority consider requiring the adoption of central procurement for solder materials.
The task force will issue a final report in October.
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