Reading a Pump Performance Curve Without the Jargon

A performance curve is the single most useful document in pump selection, but the first look can be intimidating. Once you know what each line means, it becomes a map.

The main curve plots head (vertical axis) against flow (horizontal axis). As flow increases, the head a pump can produce falls — that downward slope is the pump's character. Your operating point is where this curve crosses your system's demand.

Overlaid on that are efficiency lines, often drawn as arcs. The peak is the best-efficiency point (BEP). Selecting a pump so your operating point sits near BEP saves energy and reduces vibration and wear. Running far to the left or right of BEP shortens pump life.

Power curves tell you the horsepower the pump draws across the flow range, which sets your motor size. NPSH-required curves, usually near the bottom, show how much suction margin the pump needs at each flow — compare it to your system's NPSH available to avoid cavitation.

When you compare two pumps, look past the headline flow number and check where each one's BEP lands relative to your actual duty. The pump whose sweet spot matches your system will almost always be the better long-term buy.