Friday, 6 October 2017

Bukit Batok water pipe leaks caused by corrosion, says PUB

Investigations are ongoing; works start this week to replace 170m of pipeline in St 21 area
By Lin Yangchen and Tan Tam Mei, The Straits Times, 5 Oct 2017

National water agency PUB is checking all 100km of water pipes in Bukit Batok after initial observations found that corrosion caused two water pipes in the estate to burst in the span of less than a week.

Investigations into the incidents are ongoing, including what caused the pipes to corrode, added PUB yesterday, even as it looks to speed up a project to renew old water pipes islandwide.

On Sept 26, and then on Sunday, pipes had burst in Bukit Batok West and Bukit Batok East, respectively. Water spouts rose several storeys and caused localised flooding.

Mr Michael Toh, director of PUB's Water Supply (Network) Department, told reporters during a site visit to Bukit Batok that both pipes were laid in the 1980s, when Bukit Batok New Town was being developed.

The pipe that burst in Bukit Batok West was a 700mm-diameter high-pressure steel pipe and supplied water to the whole Bukit Batok estate.

The one in Bukit Batok East was a smaller 150mm ductile iron distribution pipe.

Starting later this week, PUB will replace 170m of pipeline within the Bukit Batok Street 21 area, which includes Blocks 222 and 223, where the most recent incident occurred. The works are expected to be completed by the end of the year.

PUB will also examine the condition of the old pipes that will be dug out in Street 21 before deciding whether to step up the frequency of inspections elsewhere in the estate.

Mr Toh said the pipes in the estate were checked in January, in accordance with PUB's practice of checking all pipes in Singapore at least once a year.

He said that although the two recent leaks in Bukit Batok were quickly detected by wireless sensors installed throughout the potable water pipe network, water continued spouting for a while because the agency was rerouting water from other pipelines to ensure an uninterrupted supply to customers.

In response to additional queries, a PUB spokesman said pipe leaks could also be caused by wear and tear due to age, damage from other works in the area, soil settlement and pipe corrosion due to high water table or high salinity in the soil.

Singapore experiences about six leaks per 100km of pipes a year, down from 95 leaks per 100km in 1985. Around 5 per cent of the water supply is "unaccounted for" - lost through events like leakage, firefighting, maintenance and others.

This beats many other developed cities: According to a report by the Smart Water Networks Forum, unaccounted-for water in 2011 stood at 25 per cent in Hong Kong and 28 per cent in London, for example.

Associate Professor Tan Soon Keat of the Nanyang Technological University's School of Civil and Environmental Engineering, said zero pipe leak or burst incidents is not possible, and detecting them has always been a challenge.

"With the system we have, occasional leaks are inevitable.

"Our agency (PUB) has an excellent and responsible response team that is the envy of many other places," said Prof Tan.

PUB is looking into acoustic technology that would enable the agency to identify worn-out pipes with thinning walls that could be on the verge of springing leaks.

"Water is precious and leaks are disruptive, so all the more we need to prevent them," said Mr Toh.

PUB has a pipeline renewal programme that began in the 1980s, replacing unlined cast iron pipes laid during colonial times with more robust materials such as cement-lined, polyurethane-coated ductile iron and steel pipes.

Last year, it renewed 20km of pipelines. It said it would accelerate the programme, and aims to renew an additional 125km of its 5,500km of potable water pipes by 2019.

Additional reporting by Tan Tam Mei

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