The working principle of the self-priming pump is that the pump casing is filled with water before the pump is started (or the pump casing contains water itself). After starting, the impeller rotates at high speed to make the water in the impeller channel flow to the volute. At this time, the inlet forms a vacuum, which opens the water inlet check door, and the air in the suction pipe enters the pump and reaches the outer edge through the impeller channel.
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