Replacement of bitumen-lined water pipes ‘part of Hong Kong’s long-term plan’

Hong Kong authorities will replace old pipes lined with bitumen in the long run and are planning to increase cleaning efforts, an official has said, after test results confirmed the presence of the banned substance in the water supply at two public housing estates.

But the government’s late response failed to ease worries of residents, who said black particles were dissolving in the water and becoming sticky, questioning whether filters could do the job.

Bitumen, which has been found in the freshwater supply at Queens Hill Estate and Shan Lai Court in Fanling, is a substance produced through the distillation of crude oil and known for its waterproofing and adhesive properties. It has been banned from use in water pipes since 2005.

“It is obvious that the black particles have decreased after the Housing Department added the filters,” Director of Water Supplies Roger Wong Yan-lok told a radio programme on Friday.

Asked if the government would replace the ageing pipes, Wong said it was part of the department’s long-term plan.

“We will replace the pipes in a risk-based approach in the long term,” he said, adding that 700km (435 miles) of water pipes in the city were lined with bitumen.

The government has been accused of a slow response in delivering water test results and addressing residents’ concerns. Wong and a Housing Department head only confirmed bitumen had been found in the water supply on Thursday, five days after residents filed complaints and a day after a test commissioned by two media outlets showed the same results.

Wong could not give a definite answer for when all the black particles would be cleared, but said authorities would increase cleaning efforts in estates using the older pipes.

According to the water examination report for the two estates published by the department on Friday afternoon, all water samples collected between last Friday and Thursday were free of carcinogenic substances and not poisonous. The results also showed that the appearance of the water was clear.

Wong said he believed the bitumen came from a 400-metre-long (437-yard) steel water pipe laid in an upstream area, 2.6km away from the public estate, in 1987.

The substance could have lingered after Queens Hill Estate was used as a Covid-19 quarantine facility in 2022, when authorities received reports that a large amount of sediment was flowing in its pipes, he said.

Authorities had cleaned the pipes and installed filters to stop particles larger than 0.1mm from entering the estate’s pipes in December that year, he added.

Wong said the pipes in Queens Hill Estate were relatively large, with the one linking the two estates being 800 metres long. New development areas nearby would also share the same pipe system.

“If the water flow is not sufficient, sediment can easily accumulate,” he said.

Wong said he would discuss with the Housing Department whether to increase the frequency of washing in the future and ensure it would be done regularly and according to the established procedures.

The department said it had installed 22 filters in the estates’ pipe system to further remove particles larger than 0.1mm from the water.

Residents earlier said that they had to resort to buying bottled water, as the government’s cleaning work had not removed all particles.

A resident, surnamed Chan, said on another radio programme that households were still concerned about safety and worried that the filters might not be working.

“The particles are sticky and dissolved in the water,” he said, adding there were fewer particles than on the previous days.

Wong said the water was still safe for consumption, according to the government’s tests.

Lawmaker Judy Chan Kapui called on authorities to suspend the water supply and thoroughly clean the pipes in one go.

“I hope the government will consider replacing the ageing pipes to prevent similar situations,” she said.

A specialist in emergency medicine, who declined to be named, said bitumen could be more concerning for human health if it was in the form of vapour.

“There is a lot of vapour when bitumen is used for road surfacing. [The vapour] is more easily to be absorbed by human body,” the medical expert said. “But those small particles [in the water] are inert … meaning it is unlikely for them to be absorbed or turned into something else.”

“Usually they would just be passed out in faeces.”

He said the water could be consumed after it hds been filtered, as bitumen was not soluble.

Black particles were also reported in the past, including in Kwun Tong’s Sau Mau Ping Estate in 2018 and Shau Kei Wan Oi Tung Estate in 2017.

Particles detected at Shau Kei Wan Oi Tung Estate were confirmed to be bitumen.