Abstract: A system is provided for pumping high pressure power liquid for a downhole hydraulic pump for producing fluids from an oil well. The power liquid is mixed in the well with the produced well fluid and is conveyed to a phase separation vessel at the surface where gas, oil and water are gravity separated. Power liquid is withdrawn from this vessel to the inlet of a combined pitot pump and centrifugal cleaner. This combined pump and cleaner has a stationary housing and a rotatable cleaning chamber. A stationary pitot tube in the rotatable housing provides pressurized clean power liquid for the suction inlet of a high pressure multiplex piston pump that feeds power liquid to the downhole pump. The rotating chamber has passages at its periphery for discharging dirty liquid which drains from the housing and is pumped to a production flow line. Fluids from the phase separation vessel are also recovered through the production flow line.