Water Supply Disruption in Clementi Town

Dr Tan Wu Meng asked the Minister for the Environment and Water Resources (a) what are the causes leading to the water supply disruption in Clementi Town on 28 October 2015; and (b) what are the actions taken by PUB to prevent a similar occurrence from recurring.

Dr Tan Wu Meng asked the Minister for the Environment and Water Resources how does PUB determine the deployment of water wagons and an onsite technical team during a water supply outage.

The water supply disruption in Clementi Town on 28 October 2015 was caused by an unexpected closure of a valve on a key pipeline supplying water to the Clementi Town. PUB was carrying out upgrading works of the control system to the valve when a software glitch occurred. This resulted in the unexpected closure of the valve and interrupted water flow into the distribution network.

For such upgrading works, PUB follows the industry practice of factory testing, followed by site-testing prior to the commissioning of the works. Following this incident, PUB has tightened its testing and commissioning processes to prevent the recurrence of a similar incident. The upgraded control system has since been commissioned.

On the deployment of water wagons, PUB operates a 24-hour centre to receive, respond and monitor customers' feedback. Water wagons are deployed by the centre when there is a water supply disruption affecting a large number of customers. PUB's technical crew is deployed for all water supply-related feedback which requires on-site attention, for example, to check water pressure and quality.

In the incident on 28 October 2015, the customers affected were located at the lower floors, which receive water directly from the PUB mains. Upon receiving feedback at 5.40 pm, PUB had immediately deployed service vans and water wagons to the premises. The water supply was progressively restored from 6.40 pm, after PUB officers reopened the affected valve. Customers on higher floors were not affected as they get their supply from the rooftop water tanks.