Firefighters were called to Accrington Victoria Hospital after a water pipe burst.
The fire alarm went off inside the dialysis unit after steam from the water leak activated the alarm.
Crews from Hyndburn arrived at 5am and spent around an hour clearing up the water.
Tony Spencer, watch manager, said the unit was closed at the time and nobody was injured or evacuated.
He said: “The fire alarm went off caused by steam from a leaking hot water pipe.
“We spent an hour squeezing the water out so it could open again in the morning.
“The water pipe was suppling one of the dialysis machines. The unit was shut at the time.”