The multistage pump needs to add water before starting
The centrifugal pump can only exert centrifugal force on the water body when the impeller rotates when it is filled with water. The water body obtains energy through centrifugal force, and the pump can play its role with the flow rate and head. If the unused multi-stage pump is not filled with water before starting, the impeller of the multi-stage pump only drives the air in the pump to rotate, because the weight of the air is very small, the centrifugal force generated is too small, and the multi-stage pump cannot be separated from the pipe. All the air in the road is exhausted, that is, no vacuum can be generated in the multi-stage pump, so the water cannot be sucked up.
