More than 20,000 people are without water and might not have it all day.

The incident was caused by “unusually low levels of chlorine” at Southern Water’s Hardham water supply works near Pulborough which meant the site had to be shut down.

The site was shut down last night at around 9pm.

Southern Water apologised to people and said it is trying to restore the water supply as soon as possible.

The Argus: Nineteen tankers are being used while water supply issues continueNineteen tankers are being used while water supply issues continue

The number of people without water is expected to rise to 40,000 by lunchtime.

People have no water supply in Horsham, Billinghurst, Broadbridge Heath, Pulborough, Codmore Hill, West Chiltington, Wisborough Gree, Rudgwick, Loxwood, Barns Green and Slinfold.

The water supply should be back to normal by tomorrow.

A spokesman for Southern Water said: “We're very sorry to our customers who are without water - we're doing everything we can to restore supply as soon as possible.

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“The incident was caused by unusually low levels of chlorine being detected at our Hardham water supply works on Saturday.

“Although this did not impact customers, we had to shut down the site and as a consequence, are currently unable to supply water to approximately 20,000 customers in West Sussex. 

“We anticipate that this number will grow during the morning, and could reach 40,000 at around lunchtime.  We're doing everything we can to fix this and return the plant to service. We hope supplies will begin to return early this evening, and be back to normal within the next 24 to 36 hours.

“We've already started deliveries to our most vulnerable customers on our priority services register, and have a fleet of 19 tankers already supporting hospitals and supply where most needed. Bottled water stations will be open today.”

There is a bottled water station open at Billingshurst Football Club.