A submersible pump assembly includes a centrifugal pump driven by a motor. The pump has a number of stages, each of the stages having a diffuser and an impeller. An upthrust washer is located between a diffuser upthrust surface and an impeller upthrust surface. Balance holes extend from an inlet on an upper side of the impeller to an outlet within one of the impeller passages. The upthrust washer overlies the inlets while the impeller is in the upthrust position. Slots are located at an interface between the upthrust washer and the impeller upthrust surface. Each of the slots registers with the inlet of one of the balance holes to allow fluid flow into the inlets of the balance holes while the impeller is in the upthrust position.