Are centrifugal pumps self-priming?

Centrifugal pumps by their design are not inherently self-priming. A centrifugal pump relies on the presence of liquid to create the necessary hydraulic conditions to lift and move fluid. When a centrifugal pump is initially started, it must be filled with the liquid it is intended to pump; otherwise, it cannot build sufficient pressure at the inlet to start pumping.

If a centrifugal pump operates in a situation where it loses its prime (for example, if the fluid in the suction line is drained), it will not automatically re-prime itself without manual intervention. This characteristic distinguishes centrifugal pumps from self-priming types, which can automatically evacuate air from their suction line and allow for fluid to enter the pump even after a loss of prime.

Some centrifugal pumps can be modified or designed specifically to be self-priming, often including features like an integrated chamber to hold a certain volume of liquid, allowing them to manage air and restart pumping more easily. However, this is not typical for standard centrifugal pumps. Hence, stating that they are not self-priming is accurate for the general category of centrifugal pumps.