When there is air in the centrifugal pump housing, there is less centrifugal force due to the density of the air being much less than the density of the liquid. Thus, the tank above the liquid level and the pump inlet pressure difference is not enough to liquid storage tank pressure into the pump, that is, centrifugal pump without self-suction capacity, so that the centrifugal pump can not deliver liquid, a phenomenon called "gas tied phenomenon". In order to fill the centrifugal pump with a liquid, a bottom valve with a strainer is usually provided at the bottom of the suction pipe. The bottom valve is a check valve. The filter serves to prevent the solid matter from entering the pump to damage the impeller or impede the normal operation of the pump. This article Keyword search: more pump valves Product Information hangzhou mankun imp. exp. co., ltd. , https://www.multihz.com