• If any centrifugal pump consists of two more impellers, the pump is called a multistage centrifugal pump.
• Some impellers may be mounted at the same shaft practically on different shafts.

Some multistage pumps is having the following two important functions

1. To produce each high head and
2. To discharge each large quantity of liquid.

• Some of a high head is to obtain developed, that impellers occur connected in series (or on that same shaft) while during discharging large quantity of liquid some impellers (or pumps) remain connected in parallel.

• As developing a high head, several impellers are mounted in series either on the identical shaft as shown in Fig.
• This water from the suction pipe enters a specific 1st impeller at the inlet and also is discharged at an outlet with increased pressure.
• Proper water with increased pressure from every outlet of the 1st impeller is taken toward the inlet of the 2nd impeller including each help of a connecting pipe as shown in Fig.
• About the outlet of the 2nd impeller, some pressure of water directions is higher than the pressure of water at the outlet from the 1st impeller.
• Therefore if more impellers are mounted at the same shaft, the pressure to the outlet will be increased further.

Fig. Two-stage pumps with impellers in series

n = Number from identical impellers mounted toward the same shaft,

Hm = Head developed by each impeller.

Then the total head developed

Each discharge passing through each impeller remains the same

• To obtain a high discharge, the pumps should be connected in parallel as shown in Fig.
• Several of the pumps lift the water from a common pump and also discharges water to a general pipe to which the delivery pipes of a specific pump are connected.
• Every one of the pumps is working against each same head.

Fig. Pumps in parallel

n = Number from identical pumps arranged in parallel,

Q = Discharge of one pump.

Then discharge