ordinary centrifugal pump, if the suction fluid is under the impeller, it should be irrigated in advance, which is very inconvenient. in order to pump the water in the pump, the inlet of the suction tube requires the bottom valve, and the bottom valve causes a large hydraulic loss when the pump works. alleged self-priming pump, it is before start without irrigation (the first time you start after installation to infuse water still), after a short time, by the pump itself, namely can suck up the water, into the normal work.
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