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Pump Performance Curve: What It Is & How to Read It

  • Posted on 28/05/2026
  • by Keith Pearson
  • Pumps
10 min read

A pump performance curve (also called a pump curve) is a graph published by the manufacturer showing how a centrifugal pump’s head, efficiency, power draw, and NPSH required change as flow rate increases. Reading it correctly is the most reliable way to confirm a pump will deliver the flow and pressure a system actually needs, without wasting energy or running outside its safe operating range

What the Curve Actually Shows

A typical pump performance curve plots several values against flow rate (measured in L/s or m³/hr) on the horizontal axis:

  • Head curve – the pressure (in metres or kPa) the pump can generate at a given flow rate. Head falls as flow rises.
  • Efficiency curves – concentric “islands” showing pump efficiency (%) at different combinations of flow and head.
  • Power curves – the motor power (kW) required at each point on the curve.
  • NPSH required (NPSHr) – the minimum suction pressure needed at the pump inlet to avoid cavitation, plotted as a rising line against flow.

Why the Performance Curve Matters

Selecting a pump without checking its curve against your actual system conditions is one of the most common — and most expensive — mistakes in HVAC and water system design. The curve matters because it lets you:

  • Confirm the pump can hit the required duty point (design flow and head) before it’s installed.
  • Avoid running the pump inefficiently, which drives up energy costs over the life of the system.
  • Prevent cavitation and premature wear by keeping NPSH available above NPSH required.
  • Stay inside the manufacturer’s allowable operating range, avoiding vibration, seal failure, and bearing damage from running too far left or right of the best efficiency point.

FAQ

What is a pump performance curve used for? −

It’s used to confirm that a specific pump can deliver the required flow and head for a system, while operating efficiently and within a safe range, before the pump is purchased or installed.

What is the best efficiency point (BEP) on a pump curve? +

BEP is the flow rate at which the pump operates at its highest efficiency, converting the most input power into usable head and flow with the least wear on components.

What happens if a pump runs outside its curve’s operating range? +

Running too far from BEP increases vibration, heat, and mechanical stress, which can cause premature seal, bearing, and shaft failure — even if the pump still technically meets flow and head requirements.

How does Masterflow help select the right pump using performance curves? +

Masterflow matches your system curve against manufacturer pump curves using the Pump Selector tool, confirming duty point, BEP proximity, NPSH margin, and motor sizing before a pump is specified.