Proactive methods and articles of manufacture are disclosed for preventing any water leak or flooding of a toilet. These methods and systems can replace or be added to the water system of existing toilets, especially the North American toilets, which use water tanks. In various embodiments the water is turned OFF and prevented to enter the toilet tank before the flush handle is activated and/or before a user is sensed. In some embodiments each flushing of the toilet permits the toilet tank to only fill once. If a leak causes the tank to empty, water is not permitted to fill the leaking tank until the next time the flush handle is activated. In some other embodiments each flushing of the toilet and/or sensing of a user permits the toilet tank to fill a predetermined number of times.