Abstract: A fire hydrant break off valve includes an offset pivot and a lateral trigger captured between a fire hydrant and fire hydrant break off riser. When a collision breaks the break off bolts holding the fire hydrant to the hydrant break off riser, the lateral trigger is released and the valve rotates to a closed position. Force of water attempting to escape rotates the valve around the offset pivot. The edge of the valve is tapered and after rotating, the valve is pushed against a matching seat to close the valve. The match of the tapered valve against the tapered seat stops or nearly stops all flow of water from the broken hydrant.