The self-priming of the self-priming pump refers to starting the pump without filling water in the suction tube (but there must be enough water in the pump body). It has the function of starting to remove the gas in the suction pipe and steps into normal operation after a very short period of time. The self-priming pump must be filled with sufficient water before the first start-up, and then start again by the water left in the pump body to work normally.

Ⅰ，Principle and performance characteristics of self-priming pump.
Self-priming centrifugal pump is a kind of self-priming centrifugal pump with compact structure, convenient operation, stable maintenance, high efficiency, long life and strong self-priming capacity. The bottom valve does not need to be installed in the pipeline, just make sure that the pump body has quantitative injection before working. Different liquids can be self-priming pumps.

Ⅱ，the difference between self-priming centrifugal pump and centrifugal pump.

1. Before starting, the self-priming centrifugal pump first begins to inject a certain amount of starting circulating water into the pump body. each time the centrifugal pump starts, it must fill the water inside and inside the pump body at the same time, or use an auxiliary device to pump into the inlet pipe.

2. On this device, the self-priming centrifugal pump is equipped with a filter screen and no bottom valve at the bottom of the intake pipe, and the centrifugal pump must be equipped with a bottom valve at the lower end of the intake pipe.

3. When running, the efficiency of the self-priming centrifugal pump is generally lower than that of the centrifugal pump, and the cavitation performance of the pump with the same performance parameters is poor.

Ⅲ，when the gas-liquid mixed self-priming centrifugal pump is working, three processes must be completed:
1. the gas in the impeller is output back and forth from the impeller, and the gas-liquid self-priming centrifugal pump is divided into internal and external mixing according to the different parts of water-gas mixing.
2. The water flow in the gas-liquid separation chamber returns to the impeller inlet, and the gas and water are mixed at the impeller inlet.
3. The water in the gas-liquid separation chamber is returned to the outlet of the impeller, and the gas and water are mixed in the external aid of the impeller, which is called the external mixing self-priming centrifugal pump.