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“True culprit” of lead in Hong Kong tap water: copper throat solder

The lead-water turmoil has been in trouble for more than two months, and finally it is determined that the “lead culprit” is that the tin soldering material of the copper throat contains lead. A task force established by the Hong Kong government to investigate excessive lead in drinking water released preliminary results on September 25. It was found that samples of copper throat welding positions at Kang Ching House, Kai Ching Village contained 41% of lead, 585 times higher than the British standard. The task force did not respond to whether the contractor involved will be held accountable through legal channels, but only made a number of suggestions, including the use of central procurement of welding materials in the future, so as to reduce the downstream mistaken purchases.

In the past two months, the task force inspected the second phase of Qiqing Village and Kwai Lian Village where the lead content in drinking water exceeded the standard, and removed more than 100 internal water supply system components, including 44 copper pipes, 28 gates, and 3 The water meter, 12 faucets and 47 welding positions were transported back to the laboratory for various tests, during which the stainless steel hoses were used in Hong Fuk Village, Yuen Long, for comparison tests.

The task force stated that since it has inspected the underground water tanks and rooftop water tanks of the second phase of Kai Ching Village and Kwai Lian Village, it was found that there was only less than 1 microgram of lead per liter of water, and the water pipes from the underground to the rooftop were made of cast iron pipes. No welding is involved, so there is reason to believe that the water delivered from government water pipes to buildings is lead-free. The main object of this investigation is the copper pipes that go down from the rooftop to each floor.

The task force member Chen Hanhui explained that the release test is to inject water into the components for 24 hours to calculate the total amount and specific gravity of lead released from each component of the entire water supply chain. The release test results found that in the water supply chain of Kang Ching House, Kai Ching Village, lead was released from copper alloy gates, faucets, and copper pipes/soft soldering positions with a diameter of less than 76 mm. Among them, the release amount of soldering positions was the highest. The material analysis showed that the lead content was 41%, which was 585 times the lead content of 0.07% in the British standard.

The task force also determined that the lead content in the drinking water in the two villages exceeded the standard and was not caused by copper alloy plumbing installations. The team conducted a scientific analysis of lead isotope and found that the lead isotope ratios of lead-tin soldering materials and copper alloy plumbing fixtures clearly belong to two different groups, and the isotope of lead-containing soldering materials and water samples with excessive lead content The averages are very consistent. In other words, the lead in the water comes from lead-tin soldering materials.

In addition, the task force discovered that some contractors had turned their backs on their own. The gates and faucet brands actually installed in some public housing estates were not the same as those originally submitted to the Water Supplies Department. The team secretary and assistant director of the Water Supplies Department, Leung Chung-li, stated that the brand of the gate switch used in Kai Ching Village is different from the declared brand, and the lead content of the gate switch does not meet the British standard. The team will follow up with the relevant material supplier. Do not rule out removing it from the approved list.

In order to prevent the occurrence of lead in drinking water, the task force made a number of recommendations, including adequate and regular site inspections by qualified persons from the Buildings Department; use of rapid lead testing or X-ray fluorescence spectrometers for welding positions; and requirement for a license Plumbers and authorized persons have added four new parameters to the water quality test of the newly completed internal water supply system, namely lead, chromium, cadmium and nickel; it is recommended that the Housing Authority study the use of centrally purchased welding materials; and it is recommended that the Water Authority study Review relevant legislation.

The task force is expected to publish its final investigation report in mid-October. The task force also tested the release of three other heavy metals, including cadmium, chromium and nickel from all parts of the water supply system. The results showed that nickel was detected in the kitchen and washing machine taps of the Kangqing House unit in Kai Ching Village. However, there is only a small amount of water in the faucet, and the nickel can be washed away after a second or two. The release test results of cadmium and chromium in each device are below the detectable level, that is, the content is less than 1 microgram per liter of water.

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