Self-priming Pumps are a type of end-suction centrifugal pump which can operate in a suction-lift configuration without requiring an external priming system.
Since they operate by imparting velocity to a liquid, they must be filled with liquid in order to operate. However, there is a special type of centrifugal pump that can evacuate the air from its suction line. This type of pump is called a self-priming pump.
Solids handling is one of its most important advantages, as some self-priming pumps can handle solids up to 3 inches.
Another advantage, when compared to a submersible pump, is its ability to continue pumping fluid while pump is still situated out of the pit.
How do Self-Priming Pumps Work?
Self-priming pumps are designed with a large reservoir surrounding the pump casing. When the pump is energized it begins to attempt to pump the water in the casing that was retained after the last time the pump ran. As the water is pushed out of the casing, air is drawn into the suction of the pump. Since the casing is not full of water, the water being pumped exits the casing but does not exit the reservoir. Instead, the water drains back into the casing, but the air carried with the water separates and is pushed out of the pump as more air is pulled into the suction of the pump.