Abstract: An automatic fluid-sensing and fluid shut-off system (10) that allows a flow of water into a structure to be sensed, timed and stopped when the flow exceeds a preset time. The system (10), which operates in combination with a conventional main water valve (50) and pressure regulator (60), consists of a flow-sensing valve (12) that incorporates an infrared emitter (14) and an infrared detector (16), an electric valve (18) and an electronics control unit (20). When a flow is sensed by the valve (12), the detector (16) produces a flow-trigger signal that is applied to a programmable timer (20n) in the unit (20). When the signal is received, the timer commences a countdown; when the time has lapsed, the unit (20) produces a signal that energizes a power relay (20h) that removes the power keeping the electric valve (18) open. Upon this power removed, the valve (18) closes and shuts off the water supply. The water flow remains off until the system is reset by depressing a reset switch (20t).