A primary school closed early on Thursday afternoon after a water main burst in Fylde.
Taps ran dry across Ansdell shortly after lunchtime.
The problem was reported to United Utilities at 1.54pm and the water company said engineers were aiming to get the supply restored as quickly as possible.
Ansdell Primary School in Landsdowne Road texted parents to say it was closing shortly after 2pm, just over an hour ahead of the usual finishing time for its 240 pupils.
Headteacher Mandy Colligan said: “With no water for toilets or washing hands we just had to take the decision to close.
“It is very unfortunate but we had no choice and we hope to be back to normal tomorrow.”
The water supply was also cut off at nearby Lytham St Annes Technology and Performing Arts College – Fylde’s biggest school with 1,400 students – but it stayed open as normal to the usual 3.10 finishing time.
A careers evening at the college went ahead as planned.
A spokesman said: “The water has been off here but with it happening so close to the end of the school day we managed to limp through without having to close.”
Water tankers were later seen on Smithy Lane and Blackpool Road and a spokesman for United Utilities said: “The water supply problem was caused by a burst water pipe within a field in the vicinity of Moss Hall Lane.
“We deployed engineers who have managed to move water around the network to bypass the damaged pipe, which will help restore water supplies.
“Over the course of the afternoon and early evening water supplies will return to normal and work to repair the water pipe will be on-going.
“We’re very sorry for this disruption.”