Self-priming centrifugal pump works is: before starting the pump pump filled with water (or the pump itself has water). After the start of high-speed rotation of the impeller so that the impeller channel flow of water to the volute, then the entrance to form a vacuum, the inlet valve against the open, the suction pipe into the air within the pump and reach the outer edge of the impeller channel. On the other hand, the water drained by the impeller into the gas-water separation chamber flows back to the outer edge of the impeller through the left and right return holes. The water flowing back from the left backwater hole is directed to the impeller channel under pressure difference and gravity and is crushed by the impeller. After mixing with the air from the suction pipe, it is thrown to the volute and flows in the direction of rotation. Centrifugal force is actually high-speed rotation of the impeller, water and air at high speed rotation, resulting centrifugal force.