Some embodiments of the present invention provide a pump including a pump housing having an inlet adapted to fluidly couple with an inlet conduit, and an outlet adapted to fluidly couple with an outlet conduit. The pump also includes a pump shaft rotatably supported in the pump housing and a plurality of impellers coupled for rotation with the pump shaft. The pump further includes a motor removably coupled to the pump housing. The motor has an output shaft drivably coupled to the pump shaft. The pump also includes a spacer positioned between the plurality of impellers and the motor. The spacer includes at least one aperture to access and de-couple the output shaft and the pump shaft. The motor, spacer, pump shaft, and the plurality of impellers are removable from the pump housing as a single unit without disconnecting the inlet conduit and the outlet conduit from the pump housing.