Abstract: A valve adapted to be disposed in a conduit for a flowing substance which may be a liquid or gas comprises a lower valve housing for allowing fluid under pressure to enter the valve. As flow under pressure enters the valve body it forces a float ball to float inside the valve body. When a rupture in the conduit occurs and allows the flowing substance to exceed the normal amount of pressure, the float ball rises to and engages an upper valve housing ball seat where the float ball sits thereby sealing and shutting off the valve from escape of the flowing substance. When the problem has been rectified, the valve can be reactivated by removing a lock member and simply pressing a reset button.