How to Choose a Pump | Start With the Duty Point

Need to move water for irrigation, lawn treatment, or drainage? Most of how to choose a pump comes down to the job’s duty point, not the sticker price. Flow and pressure decide whether the pump works at all; efficiency and materials decide whether it lasts. The same care applies to nursing pumps, where the U.S. Food and Drug Administration (FDA) says intended use and shield fit matter most.

Choosing a Pump Starts With the Duty Point

Every selection starts with two numbers: the flow rate the system needs and the total head the pump must overcome. The U.S. Department of Energy (DOE) advises measuring actual flow and head and building a system curve instead of guessing from pipe size.

• Flow rate: how many gallons per minute the system demands. Add up irrigation zones, fill times, or fixture counts; this is the vertical axis of a pump curve.
• Head: the total energy needed to overcome elevation change, friction loss, and outlet pressure. Compare pumps by head in feet rather than wattage.
• Duty point: the exact flow-and-head combination the job requires. A pump with an impressive nameplate can still miss this point.

Head is not the same as vertical lift. Long runs, narrow pipe, elbows, and valves all add friction, so the same 20-foot lift can require far more head in a real installation. When in doubt, use a pressure gauge to check what the system actually needs.

How Much Pump Do You Actually Need?

Plot your system curve, compare it with the manufacturer’s pump curve, and find where the two meet. Ideally, that operating point sits near the pump’s best efficiency point (BEP). A pump that is too large runs off BEP, wastes electricity, and can damage the impeller. The DOE pump selection guide recommends choosing a pump that stays efficient across the expected operating range and reviewing lifecycle cost instead of purchase price only. It also calls for NEMA Premium efficient electric motors.

On suction-lift installations, verify that available NPSH exceeds required NPSH. When available NPSH falls below required, water flashes to vapor inside the impeller and causes cavitation — a loud, destructive failure that also cuts efficiency.

Then match wetted materials to the liquid’s viscosity, specific gravity, temperature, solids, toxicity, and volatility. A pump built for clean water can fail quickly on muddy irrigation supply. Finally, confirm the physical fit: pipe connections, voltage, dimensions, and service clearance.

Choosing a Breast Pump: Follow the FDA’s Criteria

For breast pumps, the FDA recommends choosing a model based on intended use, how long each pumping session runs, where you will pump, portability, and how well the breast shield fits. The agency also says to review the assembly, use, and cleaning instructions before you buy.

Shield fit and easy cleaning usually decide whether a pump gets used consistently. If the shield is uncomfortable or the parts are hard to reassemble, daily pumping becomes a chore. Comparing electric models? Our tested roundup of electric nursing pumps covers fit, portability, and how the controls actually work.

Either way, the same habit works: define the duty point or use pattern, verify the fit, and weigh efficiency and practical usability against the price.