Patent ID: 8517699

Claim:
A pump, comprising: (a) an elongated pump housing having first and second ends; (b) a centrifugal primary impeller mounted in the housing for rotation about an axis, the primary impeller comprising a plurality of vanes whose outer tips define an impeller plane; (c) an inlet disposed in fluid communication with the primary impeller; and (d) a volute housing extending in a spiral shape around the pump housing, the volute housing communicating with the primary impeller and with an outlet, the volute housing extending radially beyond axially-adjacent portions of the pump housing relative to the axis, where the volute housing is axially offset from the impeller plane, such that the volute housing is separated from the primary impeller in the axial direction by a cylindrical portion of the pump housing; wherein the primary impeller is carried at one end of a generally cylindrical rotor and a secondary impeller is carried at a second end of the rotor.