Pumps

A pump including a stator, a rotor mounted within the stator and comprising a frusto-conical first chamber, a second chamber axially aligned with said first chamber and lying adjacent the end thereof having the larger diameter, a first centrifugal impeller arrangement secured between said chambers, the larger end of the frusto-conical first chamber being adjacent said impeller arrangement and the smaller end of the frusto-conical first chamber defining an inlet for the pump, a hollow member having a substantially cylindrical axial through passage mounted co-axially within the second chamber, the diameter of said through passage being less than the smallest diameter of said second chamber, an opening at one end of said member being at the level of said impeller arrangement, a radial web securing the other end of said member to a wall of the second chamber, a second impeller arrangement mounted at the other end of said through passage remote from said first impeller for discharging fluid from said through passage, said stator having a passage therein communicating with the first impeller arrangement and with an outlet for the pump, said radial web and said other end of the through passage lying within the second chamber, and a conical element mounted within said hollow member for directing fluid to said second impeller arrangement, said second impeller arrangement being disposed between said web and said conical element.