It is thought most homes in the area have no water or low pressure
Residents in parts of Notts and Derbys have been without drinking water - with garden sprinklers being blamed.
Some homes in Mansfield and Belper had no clean water overnight and tankers were being used to boost the supply.
Severn Trent said it was a short term problem caused by garden sprinklers draining small reservoirs faster than they could be filled.
The company insisted there was no need for a hosepipe ban but asked people to water their gardens some other way.
A spokesman explained that the problem was that a reservoir storing clean drinking water had been drained and tankers would be used to help refill it.
It is thought more homes will be affected if people are not more careful when watering outside.
Jo Smith, Severn Trent's head of external communications, said: "We need people to stop using sprinklers to water their gardens.
"We would suggest that if people want to water their gardens they use watering cans or water from the dishes.
"A sprinkler uses more water in an hour than a family of four does in a day."