Funny film, probably 80s where the good guys get caught by the bad guys and tied up in a shower room with the drains blocked and the showers on (the idea is that when the room fills up they will drown.) The room fills with water and all their attempts to escape fail until another bad guy unwittingly frees them. When he opens the door the rush of water washes him down the stairs.
Similar scene in Captain Ron. Lol fun movie. Might be it.
Delicatessen? A French language film from 1991. Not quite as you describe, but close. The good guys were pursued into the bathroom, and our hero elected to block the drains and door with their clothes and break all the pipes, presumably preferring suicide to being eaten by the butcher and the other tenants.
http://www.metacafe.com/watch/mv-wqjV/delicatessen_film_bathroom_flood/