Thousands warned not to use 'high chlorine' water
Severn Trent has warned thousands of customers not to use water while it investigates problems with high levels of chlorine in its supply.
The company said it is investigating an issue at the Castle Donington reservoir in Derbyshire.
It has told residents in the DE11, DE15, DE65, DE73 and LE65 areas of Derbyshire and Leicestershire not to use water for any purpose.
A total of 3,700 properties have been affected.
Severn Trent said it did not know how long it will take to resolve the problem.
"It looks like there's been over-chlorination," a spokesman said. "Once we've got through this incident and we've flushed the water through the system, we can go back, take a look and see exactly what happened.
"A Do Not Use notice means that customers shouldn't use their water supply for any purpose - including drinking, flushing the toilet, preparing food and bathing."
Darren Reynolds - professor of health and environment at the University of the West of England (UWE) - says chlorine has been used for more than 100 years to disinfect water.
"They may add chlorine in the form of liquid or possibly a solid and they may do that directly in the reservoir or large holding tanks," he said.
"It seems to me a potential problem could have been at the point of dosing - they may have just put too much chlorine in by accident."
Affected residents said they were concerned at how long they could be without water.
Dad James Machin, from Swadlincote, Derbyshire, said: "You can get the bottled stuff but you can't wash in the bottled stuff.
"It'll be a bit of a nightmare because as well as bathing, the kids like a glass of juice too."
The company, whose website crashed earlier due to the demand for information, was alerted to the problem by a monitoring systems alarm.
Staff made bottled water available to customers at Sainsbury's in Swadlincote.
"We are now working to flush the water out of the system and are constantly testing the quality of water at customers' taps," the spokesman added.