A hydraulic system for a reciprocating piston pump that includes an accumulator for producing a steady-pressure supply of compressible material to a distribution nozzle. The hydraulic system includes an adjustable means for constricting the flow of hydraulic fluid from the accumulator to the hydraulic system. The means for constricting the flow of hydraulic fluid allows the operator to compensate for the type of material being pumped, the vertical distance the material is being pumped, as well as the overall distance the material is being pumped in order to reduce or eliminate line surge. The means for restricting the flow from the accumulator preferably includes a needle valve that allows the operator to select the flow characteristic from the accumulator.