Discoloured water that was coming out of residents' taps in Serangoon Road, Beng Wan Road and Bendemeer Road from noon on Tuesday cleared up yesterday morning, PUB said.
Residents in those areas were advised not to use the water and to instead collect clean water from five water wagons deployed at collection points near blocks 44 to 49 in Bendemeer Road on Tuesday.
Photos posted by Facebook user Jo Ee at 10.37pm on Tuesday showed people queueing up for water in Bendemeer.
National water agency PUB told The Straits Times that its officers were at the scene to help residents and to flush the water mains.
"The discoloured water is due to resuspension of mineral sediments arising from sudden flow changes within a water pipe," said PUB.
Such mineral sediments are naturally present in the water and settle down inside the pipe over time, it added.
PUB said it had isolated the section of the pipe where the mineral resuspension occurred and tapped an alternative feed to supply water to affected blocks on Tuesday night.
The agency is investigating what caused the resuspension of the sediments. Residents who need help can call PUB on 1800-2255-782.