Abstract: A plumbing fixture is provided with means for preventing flooding by obstructing the waste outlet thereof, such means being an overflow chamber along the edge of a bowl or basin, further provided with an electrical probe within the overflow chamber to complete an electrical circuit between the probe and the basin when the water level bridges the gap therebetween, thereby actuating a normally open solenoid valve to closed position for shutting off the supply of running water to the basin. The invention is applicable to a combination lavatory and water closet fixture for preventing flooding from either the bowl of the lavatory, or the bowl of the water closet, or both by providing such means for both bowls.