Yorkshire Water is mounting a "massive operation" to cope with burst pipes springing leaks around the county.
It has sent a record number of engineers out in the field tackling leaks.
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There are currently 164 men repairing leaks, said spokesman Richard Sears, and these are supported by 200 field technicians who have to take water samples.
They have already repaired over 400 bursts this week and were facing a workload of 300 more, said Mr Sears. They were repairing 160 a day.
Bursts were being prioritised so that those which lost most water were tackled first and others would have to wait. Many bursts were in Leeds which was treated as a priority area.
Water meter readings had been suspended and the readers had been diverted to look for leaks in empty properties.
"We suspect there are lots of bursts we are unaware of," said Mr Sears, "We have contacted local authorities and asked them to check on their buildings which are either empty or closed.
"North Yorkshire County Council have reported bursts in 80 of their schools.
"We are appealing also to the business community and asking them to check premises which have been closed over the Christmas break.
"The likelihood is that some will be losing water."
Mr Sears also appealed to residents to check houses which neighbours had left over Christmas. "We can shut off the supply in the street."
He said there had been one report of water gushing out of a letterbox.
Yorkshire Water was processing more clean water than ever before, continued Mr Sears, to keep customers on tap.
Some 1.6bn litres of water were going into the supply each day.
"We are moving mountains behind the scenes," he declared, "but we appeal to our customers to use water sparingly."
A loss of water in Middleton had the potential to affect 6,000 homes, largely in the Rothwell area, he added.
"It turned out to be a problem with a valve," he said, "which affected about 2,000 properties. Some lost supplies from 9pm to 9am.
"This problem is still ongoing as we discovered an air lock in the system."
Engineer also repaired a singificant burst at Parkwood Avenue, Beeston.
Christopher Wright, the curator at Thwaite Mill Museum south Leeds, said he had been without water for 11 days and was turning visitors away.
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