Why centrifugal pump can do the self-priming?

First of all, the pump head must contains water full enough to form a water pillar when the pump started to run and send out the water in the pump head. The water gets kinetic energy from the impeller to resist the atmospheric pressure outside to press the water back. When it comes to a balance, the air in the pump head will go through the water pillar and escape step by step. This decreases the pressure in the pump head and inlet pipeline and the water in the tank will get into the pump head step by step because the atmospheric pressure on the surface of the water in the tank.

Finally when the pump head is full of water, the sel-priming si completed. However, we strongly recommend to set a self-priming tank at the suction side of the pump as the prolonged dyr-running usually cause the damages to the mechanical seal or friction bearing of magnetic pump.