These valves are used to operate the pumps with minimum load in accumulator circuits or in high-low pump circuits. In accumulator circuits, when the system pressure reaches to a cut out pressure (adjusted maximum), the valve acts to divert the pump delivery to the reservoir at low pressure, thus the pump is unloaded automatically. When the accumulator pressure drops to the cut in pressure, the valve directs the pump delivery to the accumulator and hydraulic system. An integral check valve prevents reverse flow through the valve from the accumulator. In high-low pump circuits, the valve acts to unload the large volume pump with the same manner as described above during load operation of the small volume pump.