Abstract: An improved impeller and a casing for a centrifugal pump are disclosed. The impeller comprises vanes which sweep an arc around an impeller axis to provide a smooth path past the impeller and through the pump. The casing is constructed to allow maximum flow rate at the eye of the impeller then shrink the flow channel to reduce internal recirculation promote efficiency, further limiting the effect of damaging forces. The impeller is suited for use in pumps in which a high head is required and in which only low shear forces must be applied to the fluid moving through the pump.