Abstract: An overflow protection shut-off device for use with a water heater for shutting off a supply of water to the water heater when a leaking or an overflow condition occurs, the device including a valve mechanism coupleable to an input water line of a water heater and having an opened orientation for allowing flow of water within the input line and a closed orientation for preventing such flow; a water sensing mechanism positionable at a location proximal to the water heater for providing a signal when it is placed in contact with water when the water heater experiences the leaking or the overflow condition; and a switching mechanism coupled to the valve mechanism and the water sensing mechanism and with the switching mechanism being responsive to receipt of the signal from the water sensing mechanism for placing the valve mechanism in the closed orientation.