What do pump performance curves primarily illustrate?

• A. The efficiency curve with respect to flow
• B. The relationship between head and flow
• C. The material compatibility at high flow
• D. The electrical wiring diagram of the pump

Answer: (B)

Pump performance curves show how the head a pump can develop relates to the flow it delivers. The vertical axis represents head (pressure equivalent, such as feet or meters of head) and the horizontal axis shows flow rate (like GPM or L/s). The curve generally slopes downward, meaning as you push more water through the system, the head the pump can maintain decreases due to hydraulic losses and the pump’s impeller characteristics. This relationship is key because you use it together with the system curve (piping losses) to determine the actual operating point where the pump will run in a real installation.

There are usually other lines on the chart for efficiency, power, and net positive suction head (NPSH) requirements, but the central idea the curves convey is the head-versus-flow relationship. Material compatibility at high flow and the pump’s electrical wiring diagram are separate considerations not shown on these curves, which is why they aren’t the primary focus of pump performance plots.