Abstract: An apparatus and method for ensuring that the flow of water to a toilet tank is shut off. The first preferred embodiment of the invention combines a conventional float mechanism to shut off the flow of water to a toilet tank when full, with a timer mechanism to shut off the flow of water if the float mechanism fails. There is also a manual override to shut off the flow of water if both the float mechanism and the timer mechanism fail. In the second preferred embodiment, the float mechanism is in the toilet bowl, and shuts off the flow of water when the water level rises in the bowl above a certain level after the toilet is flushed, with the timer mechanism again backing up the float mechanism. In the third preferred embodiment, there are two float mechanisms, one in the tank and the other in the toilet bowl.