What is a self-priming pump and how does it work?
Priming is the addition of liquid into the pump casing which aides in the evacuation of captured air via a vent while creating a liquid seal inside the casing. A self-priming pump develops a vacuum sufficient enough for atmospheric pressure to force the liquid to flow through the suction pipe into the pump casing without priming the pump. A self-priming centrifugal pump is especially designed with a large chamber at its discharge side that acts both as an air separator that removes the air from the liquid, and a reservoir that holds residual liquid used for priming or re-priming the pump. The pump has to be primed during the initial start-up but re-priming is done automatically without outside attention. Although self-priming appears to be a desirable feature for centrifugal pumps the trade-off is that pump efficiency is slightly compromised due to certain design constraints. This type of pump is popular with intermittent service such as drainage, sewage, and similar applications, but
