Reverse Osmosis Parts Auto Shut Off 4 Way ValveUSAGE: With Reverse Osmosis Systems DESCRIPTION: It utilizes the back pressure created by the Storage Pressure Tank (or Float valve were used) to shut off the water supply to the Reverse Osmosis membrane. If your RO system is continuously having waste water flowing down the drain even after the tank is full, then you may need to replace your old aso valve with this replacement aso Valve. SPECIFICATION: 1 4" pushfit