A hose and sprinkler ban has been placed on people in Kent and Sussex.
South East Water said it had no choice after demand for drinking water reached “record levels” in June, similar to last year’s drought.
Up to 4,000 customers have been without water or with low pressure since Monday due to supply problems.
The water company had urged people to use water for essential purposes only, but has now issued an immediate ban on hoses and sprinklers.
The measures mean that the equipment will not be allowed to be used for watering gardens, cleaning cars and filling swimming pools.
It is understood that the temporary use ban can only be enforced after ten days of inquiry, meaning that after June 26, violators of the rules could be fined £1,000.
Bottle stations have been installed in the two counties and supply problems are expected to continue through Sunday.
Douglas Whitfield, South East Water’s director of operations, told BBC Radio Kent that the hot weather had caused demand to outstrip supply.
“We are pumping as much water as we can into the system, but the water is being used before it reaches customers who are currently at the end of our system,” he said.