Abstract: A pump assembly includes a manifold having an inlet port configured to be coupled to a supply pipe and an outlet port configured to be coupled to a discharge pipe. The pump assembly also includes a cartridge having a pump stack including a plurality of pumping stages. Each pumping stage includes an impeller. The cartridge extends between a first end and a second end. The first end is removably coupled to the manifold. A carrier assembly supports the cartridge. The carrier assembly moves the cartridge between an advanced position and a retracted position. The cartridge engages the manifold in the advanced position and the cartridge is disengaged from the manifold in the retracted position. Optionally, the carrier assembly may include a support frame and at least one rail. The support frame is slidable along the rail and the cartridge is supported by the support frame.