It is thought the discolouration is caused by pipe sediment

At least 10,000 homes in Merseyside and Cheshire were affected by the problem, which is thought to have been caused by sediment in pipes.

The problem is not expected to be resolved in the Merseyside area until Thursday afternoon.

Supplier United Utilities (UU) said the discolouration was not harmful and customers should not be concerned.

The Drinking Water Inspectorate has been called in to investigate the problems, which is routine in such situations.

Cause investigated

A UU spokeswoman said it had taken 10,000 calls from customers on Wednesday about the problem, which is thought to have been caused by work carried out on one of the region's major aqueducts, on Monday.

"Parts of Cheshire are getting back to normal now, but we do not expect the problem to be cleared up until about lunchtime on Thursday," she said.

"We're investigating the cause at the moment, but the work on the aqueduct does appear to have been the reason.

'Natural sediment'

"What can happen is that the water flow in the pipes can change and natural sediment in the pipes can be disturbed, which is what has caused the discolouration.

"We don't think there's any cause for concern, the water just looks unsightly. Customers do not need to take any action and should continue as normal."

WaterVoice Northwest, which represents UU customers, said it has also received calls from concerned customers.

A spokesman for the group said: "At the moment we're just advising customers to contact the company if they are concerned, but we are liaising with United Utilities to keep up to date about the situation."