US Patent 7318556 Water line safety valve

A safety valve for a lawn sprinkler system having at least one subterranean flow line and at least one head for spraying irrigation water. The valve includes a tubular member connected between the flow line and the head. The tubular member has an axial passage therethrough for the flow of water from the flow line to the head. A seat is located within the passage. A ball is located in the passage upstream of the seat. The ball is axially movable from an open position upstream of the seat to a closed position in engagement with the seat if the water flowing through passage reaches a selected flow rate. A coiled spring in the passage is in engagement with the ball for urging the ball toward the open position.