Abstract: A centrifugal pump assembly including a housing containing a pump impeller having an axis of rotation with an inlet opening for fluids generally aligned with the axis of rotation of the impeller and a discharge opening aligned with the periphery of the impeller. The impeller is attached to a drive shaft for rotation by means of a central hub which has at least one circumferentially extending surface having an edge projecting toward the inlet at a circumference radially spaced from the axis of rotation. The surface, which is progressively recessed away from the inlet toward the rotational axis, modifies fluid flow through the pump to reduce whirling motion in the inlet, thereby significantly improving efficiency of the pump.