Pumps in Parallel or Serial

For pumps connected in serial - add head, for pumps connected in parallel - add flowrates

Pumps can be arranged and connected in serial or parallel to provide additional head or flow rate capacity.

Pumps in Serial - Head Added

When two (or more) pumps are arranged in serial their resulting pump performance curve is obtained by adding their heads at the same flow rate as indicated in the figure below.

pumps in series

Centrifugal pumps in series are used to overcome larger system head loss than one pump can handle alone.

  • for two identical pumps in series the head will be twice the head of a single pump at the same flow rate - as indicated in point 2. 

With a constant flowrate the combined head moves from 1 to 2.

Note! In practice the combined head and flow rate moves along the system curve to point 3.

  • point 3 is where the system operates with both pumps running 
  • point 1 is where the system operates with one pump running

Operation of single stage pumps in series are seldom encountered - more often multistage centrifugal pumps are used. 

Pumps in Parallel - Flow Rate Added

When two or more pumps are arranged in parallel their resulting performance curve is obtained by adding the pumps flowrates at the same head as indicated in the figure below.

pumps in parallel

Centrifugal pumps in parallel are used to overcome larger volume flows than one pump can handle alone.

  • for two identical pumps in parallel, and the head is kept constant, the flowrate doubles as indicated with point 2 compared to a single pump

Note! In practice the combined head and volume flow moves along the system curve as indicated from 1 to 3.

  • point 3 is where the system operates with both pumps running 
  • point 1 is where the system operates with one pump running

In practice, if one of the pumps in parallel or series stops, the operation point moves along the system resistance curve from point 3 to point 1 - the head and flow rate are decreased.

Related Topics

  • Pumps - Piping systems and pumps - centrifugal pumps, displacement pumps - cavitation, viscosity, head and pressure, power consumption and more

Related Documents

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