Self-Priming Centrifugal Pumps
The pump suction pipe is then air-evacuated without any special external suction devices.
Centrifugal pumps without external or internal suction devices can be operated at a suction lift if the pump body is filled with water before starting the actual fluid displacement. Due to the function of a non-return valve the fluid will be retained within the pump body after switch-off.
The construction required for for self-priming capability has a negative effect on the pump efficiency.