Residents in parts of Surrey and south London have been told water supplies are “starting to return to normal” after a major fault at a water company’s treatment works.

Sutton and East Surrey (SES) Water said customers around Sutton, Morden and Epsom could be affected as it carried out “essential repairs” on Monday evening.

A statement from SES Water issued after midnight on Tuesday said when water returned it may be cloudy or discoloured.

“We are pleased to confirm that supplies are starting to return to normal,” it read.

“However, some customers may continue to experience lower pressure or intermittent loss of supply.

“Our water storage remains low in the area and therefore customers may experience further interruption to their supply.”

Two bottled water stations were set up at Bourne Hall in Ewell, Surrey, and in Upper High Street Car Park in Epsom, as a makeshift solution, while the issues at its Cheam Water Treatment Works were resolved.

Both stations will remain open throughout the night and into Tuesday.

The company had earlier said that parts of Carshalton, Cheam, North Cheam, Wallington, Hackbridge, Worcester Park, Ewell and South Croydon may also have experienced issues with their water supply.

Luke Taylor, Lib Dem MP for Sutton and Cheam, said on X, formerly Twitter, that the situation was “not good enough” and he would be monitoring the situation closely.

He said: “Despite efforts by SES teams to repair a critical valve failure and sustain the water supply through alternative measures, they have been unable to fully resolve the fault.

“Unfortunately, this means the supply across the network has diminished, and some customers may now experience interruptions to their water supply, including complete loss of service.”

SES Water confirmed it was working closely with St Helier Hospital in Sutton to support their water needs, he said.

The company said it would be looking to set up further bottled water stations on Tuesday.

An SES Water spokesman earlier said: “Following a fault identified overnight at our Cheam Water Treatment works our teams initiated a routine alternative supply plan to ensure customers’ water supply operated as normal.

“Unfortunately, our reserve levels as part of this response have not been able to maintain the supply and demand, meaning a number of customers within Sutton, Morden and Epsom are currently experiencing no water supply until this fault is fixed.”

SES Water supplies 160 million litres of water to more than 750,000 people in parts of Surrey, Kent and south London each day, according to the company’s website.

Pennon, which also owns South West Water, Bristol Water and Bournemouth Water, was cleared to buy the company for £350 million in June.