Abstract: A multiple section irrigation sprinkler system incorporating pilot operated, pressure actuated and sequenced valve assemblies incorporates controllable device to increase or decrease the water pressure in the water supply lines at a controllable rate. The system includes a dump valve to relieve the water pressure during the pressure reduction cycle to eliminate or at least greatly reduce water hammer effects. The dump valve has a flow rate substantially less than the flow rate of the device for increasing or decreasing the water pressure in the water supply lines. The dump valve is prevented from transitioning from the open position to the closed position below predetermined pressure levels selected to prevent false sequencing of the pilot operated, pressure actuated and sequenced valve assemblies.