Four fire crews from Preston, Fulwood and Penwortham were called to the remote scene on Birks Brow in Thornley-with-Wheatley around 7pm last night when a back-up diesel generator caught fire.
The blaze spread to the pumping station, causing significant damage.
A brigade spokesman said: "The water pumping station suffered a lot of damage to the point where it is out of action.
"So temporary measures are in place for supplies in the area.
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"The cause is under investigation, but we suspect it was an electrical fault in the generator which caught fire and the fire then spread to the building."