Abstract: Disclosed is a water supply control system for controlling the water supply system in a structure, such as a home or industrial or commercial building. The water supply control system typically includes an electronically controlled on-off valve to shut down the water supply to the structure, and a water pressure relief valve coupled to the on-off valve. Additional means for relieving pressure build up in the water supply system that may be included in the control system are (1) an expansion bladder, or (2) a vent pipe integral to the water supply system and terminating on the exterior of the structure, including an on-off valve electronically controlled so as to open when the water supply system is shut down and to close when the water supply system is turned on, or (3) means for disabling a hot water heater integral to the water supply system, the disabling being accomplished concurrently with the closing of the water supply to the structure.