People in parts of Blackpool will be without water for up to eight hours as part of a £70m scheme to improve their drinking supplies.
The work will be carried out in the Kimberley Avenue and Sandgate areas from 2200 GMT on Thursday.
Engineers will push large sponges through mains pipes at high pressure to clean them out and remove debris.
United Utilities apologised for the inconvenience but said it would improve the reliability of supplies.
Workers will dig small holes along the roads to access the underground main to get the sponges into the pipes, before tankers suck up the sediment forced out.
'Funded by customers'
United Utilities' project coordinator Ray Melia said: "The investment will improve the reliability of the water supply for local residents.
"We apologise for any inconvenience and would ask local residents to bear with us while we carry out this essential work.
"We always aim to cause as little disruption as possible and we need to remember this is the type of work that our customers' bills help to fund."
People living in the area are urged to switch off any gas, oil or electric appliances that are only used to heat hot water.
Once completed, water supplies may be white or cloudy but will eventually run clear, the company said.