PURPOSE: To stabilize the sprinkling amount by controlling a valve opening by the balance between a spring for pressing a valve body attached and separated by sliding in a cylinder mounted on a valve body allowing the communication between a pressure water outlet port and inlet port through a valve seat and the pressure of pressure water.
CONSTITUTION: A water valve 11 is formed of a valve box 13 consisting of an outer cylinder 17 having a water outlet port 21 and an inner cylinder 19 having a water inlet port 25 and a valve seat 25, a cylinder 14 having an air feed port 30, and a valve body 16 provided with a spring 29 and sliding in the cylinder 14. A solenoid valve is switched to close side to discharge the pressure air in the cylinder 14 from the air feed port 30. The valve body 16 is separated from a valve seat 15 by the balance between the pressing force to the valve body 16 of the spring 29 set to a value slightly smaller than general water pressure and the pressure of the pressure water from the water inlet port 25 to automatically control the opening of the water outlet port 21. The sprinkling thus can be uniformly performed.