Abstract: A leak-stopper system for water plumbing (2) has a leak-probe circuit (1) positioned in water-detection proximity to water plumbing for a building. Leak sensors (3) which include three-probe sensors (14) are spaced apart on the leak-probe circuit for conveying existence of leakage water (7) electrically to a control board (4) with electrical communication to visual signalers (5) and to a plumbing valve (6) for shutting off water to the water plumbing automatically before leakage in the water plumbing can be fixed and to indicate where one or more leaks are for being fixed to prevent water damage to a building or its contents. Preferably, electrical current to the leak-probe circuit and to the plumbing valve is from a power source that includes an isolated power source which can be a chargeable battery (9) or other DC power supplier (12) for supplying a safe level of current for a predetermined period of leak-detection time in case of power outage to the building.