Automatic Flush Valve Insert Inlet with Ring (1pc/Bag) Automatic Flush Valves optimize drip irrigation system performance by reducing maintenance and increasing dripline performance. Eliminates clogging and promotes long-term performance of the drip irrigation system. Specifications 1 Gallon Flush Valve 17mm Maximum Zone Flow Rate Per Valve Flush: 15GPM Min. Pressure: 1.5PSI Max. Pressure: 57PSI