Canned motor Pumps are designed for high head low flow application. These pumps are in the category of low specific speed pumps and are offered for the better rise in head and efficiency when compared with centrifugal pumps in similar application requirements.

The rise in the head is achieved by adding energy to the fluid as it passes around the circumference of the impeller from the suction (inlet) of the pump to the discharge (outlet) of the pump. The suction of the pump is designed to minimise head losses of the liquid entering the impeller and has relatively small low-pressure area while comparing with normal centrifugal pumps. Thus the liquid hastens to impeller tip to fill the inlet chamber and begin adding the incremental (Regenerative) head. Due to this hastening in flow, the local static pressure is reduced, resulting in a small amount of vapour formation in the form of very small bubbles. The result of this bubble formation is to fill a portion of the pump chamber with vapour which reduces flow capacity but improves rise in a head.