Single-stage or multistage pump: differences and when to use them

Centrifugal pumps split into two families by the number of impellers: single-stage and multistage. Understanding the difference is the first step to choosing well.

Single-stage: one impeller

A single impeller gives high flow at moderate head. Ideal for transfer, circulation, irrigation and cooling. In the Grundfos range these are the NB/NK and CM series.

Multistage: impellers in series

Several impellers stack up: each stage adds head, so the pump reaches high pressure at medium flow. Perfect for pressure boosting, booster sets and boiler feed. The Grundfos CR series (and electronic CRE) is the benchmark.

How to choose

• Lots of water, low pressure? → single-stage (NB, CM)
• High pressure, medium flow? → multistage (CR, CRE)

The fastest way to decide is to start from the duty point: enter flow and head in the selector and compare curves. See also the CR multistage pumps.