Almost 10,000 properties in Devon are without regular water supplies because of a burst pipe.
South West Water said about 9,500 homes and businesses in the west of the county had either lost water altogether or were experiencing lower pressure than usual.
Engineers are working to fix the problem after the rupture happened on Monday, the supplier added.
“We’ve prioritised support for our most vulnerable customers throughout and will continue to provide bottled water where it’s needed,” the company said.
A spokeswoman said the repairs could not be rushed.
“This is a large and complex system, and it needs to refill properly and safely before we can bring it fully back into supply,” she said.
“That’s why it may take a bit more time for all customers to see their water return.”
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Fred Thomas, Labour MP for Plymouth Moor View, said it was “unacceptable” for residents to be without water for more than 24 hours.
He has written to South West Water demanding urgent action including compensation, he added.
“The water outage is continuing to cause major disruption and chaos for residents across Plymouth, with thousands of people without water,” Mr Thomas said.
“We must do better in crisis situations like this to make sure residents can keep getting on with their lives.”