Abstract: A centrifugal pump includes a housing containing an impeller mounted on a shaft which is journaled for rotation within the housing. An inlet to the housing directs fluid from a supply to one end of the impeller and axially spaced first and second volute diffusers formed around the other end of the impeller receive fluid from the impeller. The volute diffusers are of different predetermined sizes designed to handle different flowrates of fluid while producing about the same pressure head. A sleeve telescoped into the housing and surrounding the impeller may be moved between extended and retracted positions to close off and open the flow of fluid into the larger one of the volute diffusers.