A single stage centrifugal pump consists of an impeller and a volute. The liquid is drawn inside at the centre of the impeller and discharged radially.Multistage centrifugal pumps have more than one impeller and volute. A three stage multistage pump will have three impellers and three volutes. The output of the first impeller will be fed to the input of the second impeller and so on.
The multistage pump can generate more pressure than a single stage pump.
For a given output pressure, the multistage pump will have impellers of smaller diameter. The efficiency of a multistage pump will also be greater than a single stage pump.
It is possible to retrofit a single stage pump assemble with a multistage assembly with minimal rework in the piping.
In certain multistage pumps, there are provisions to by pass an impeller. This may be useful for applications such as in firefighting where the pressure of the liquid will be different at different situations (based on the height of the building). In such cases, the last impeller may be bypassed and the output can be drawn before the last impeller.
Multistage pumps will have more vibration than single stage pumps.
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