Debated in Parliament on 6 Nov 2017.
Mr Murali Pillai asked the Minister for the Environment and Water Resources (a) what are the results of PUB's checks on the water pipes in Bukit Batok SMC; and (b) what are the steps it intends to take arising from its determination that the burst water pipe incidents occurring in Bukit Batok SMC in October 2017 were due to corrosion.
The pipes in Bukit Batok were last checked in January this year and found to be in good condition then. They were next due for inspection in January 2018. Following the recent leaks in Bukit Batok, the Public Utilities Board (PUB) brought forward and completed the inspection of all 100 kilometres of water pipes in the estate. We did not detect any additional leaks. Our engineers have also investigated and concluded that the leaks at Bukit Batok West Avenue 6 and Bukit Batok East Avenue 3 were unrelated. Both pipes were laid about 35 years ago in the proper manner and met the material specifications required by PUB. At the time that they leaked, they were well within their design lifespan of 70 years.
The leaks were determined by PUB engineers to have been caused by localised corrosion. This can occur in places where the soil condition is harsher to the pipe material and when the water table is particularly high, which accelerates corrosion. We have replaced the leaking section of the pipe at Bukit Batok West Avenue 6 and are replacing all 170 metres of water pipes at Bukit Batok East Avenue 3. We expect the work to be completed ahead of schedule by end-November.
PUB operates a network of 5,500 kilometres of potable water pipes to deliver water to 1.4 million customer accounts. It continually monitors, inspects and, if need be, repairs or replaces pipes to minimise the loss of water due to leaks and to ensure good water supply round the clock. Today, Singapore experiences about six leaks per 100 kilometres of pipes per year, which is among the lowest incidences in the world.
In addition to continuous monitoring using more than 300 sensors, all pipes in PUB's 5,500-kilometre network are checked physically for leaks at least once a year, or more frequently where necessary. However, as almost all our water pipes are buried between one metre and 40 metres underground, it is challenging to assess the condition of buried pipes and detect minute leaks. PUB is thus test-bedding new technology, such as acoustic sensors, to monitor the pipelines and identify those which are not in satisfactory condition. PUB is also using pipes that are externally coated with polyurethane. These pipes are more corrosion-resistant than pipes laid in earlier years.
However, despite regular monitoring and inspection, leaks do occur, due largely to localised corrosion, uneven soil settlement or damage from construction work. Whenever pipes are found to be in unsatisfactory condition, they are either repaired or replaced under PUB’s Pipe Renewal Programme. As I have announced earlier this year, PUB is increasing its pace of pipe replacement. We are on track to replace 30 kilometres of pipes this year and will be able to replace 50 kilometres a year from next year onwards, one year ahead of schedule.
While we aim to replace all faulty pipes before they fail, leaks like the ones which occurred in Bukit Batok will happen from time to time. PUB seeks to respond and fix the problem quickly, and most incidents are resolved within a few hours. Occasionally, due to the need to ensure that water supply to residents is not disrupted when leaking pipelines are isolated from the rest of the network, additional time is required to switch residents over to an alternate supply pipeline before the affected pipeline can be shut off.
Water is precious and everybody needs to do his or her part to conserve it. I would like to assure Members and Singaporeans that PUB engineers will continue to put in their best effort to maintain Singapore's water supply network and ensure good water supply to customers round the clock.
PAPERCUTS