A dialysis unit at Accrington Victoria Hospital flooded after a pipe leaked.
Firefighters said a burst pipe caused the incident at around 4.20am on Thursday, November 29.
Crew manager Don Brady from Hyndburn fire station said there was no threat to patients, but the alarm disturbed them.
He added: "The hot pipe hadn't been shut off properly. It just needed turning off so we isolated it and did that.
"A small amount of flooding was caused and steam had also been coming out of the pipe in a room in the dialysis unit. There were no patients or staff in that room but there was a lot of equipment."