Abstract: A dual-acting, reciprocating piston pump is provided which comprises a pump body formed with a passageway having an inlet and a discharge outlet which receives a piston assembly including a plunger rod carrying a valve plate or spider, a shovel rod carrying a shovel disc and a rod connector formed with a valve seat which interconnects the plunger rod and shovel rod. A tubular check valve is carried on the rod connector between the valve seat and the valve plate in sliding contact with the internal wall in the pump body formed by the passageway, which divides the passageway into an upper pumping chamber communicating with the discharge outlet and a lower pumping chamber communicating with the inlet. A second check valve is located at the inlet to the passageway in the pump body and is movable between an open and closed position relative thereto.