Self-Priming Pumps

Some centrifugal pumps need to be primed before startup. The term "priming" basically means filling of the pump casing before the pump is started. In a later section we discuss priming in more detail.

Self-priming pumps are usually used in suction-lift configurations. A self priming pump always retains some water in its casing to prime itself, when needed.

When you shut down a pump of this type, it retains some water in a chamber below the impeller.

In the illustration provided here we show the following:

A: Suction pipe
B: Discharge pipe
C: Bottom chamber where water is retained after shutdown

D: Vent plug which can be opened up to let the air out and fill the casing for startup, if necessary.