Water Pumps

How to Select a Pump

Good selection starts with the required duty rather than the motor size or connection diameter alone.

Selection guide

How to Select the Right Water Pump

Pump-selection guide covering the duty point, system and pump curves, best efficiency point, and oversized, matched, and undersized pump comparisons.

Use this guide as a starting point. Confirm the duty point and final selection with manufacturer performance data.

Key takeaways

What to Know

Scan the main ideas first. Open “Key points” only when you want the supporting details.

Swipe the cards to continue

01

Define the Required Duty Point

The first panel combines required flow and total dynamic head into one target operating point. Flow states how much water must be delivered, while head includes elevation, required outlet pressure, and friction through the complete system.

Key points 3
  • Record one flow value and its matching head value
  • Describe temperature, solids, corrosiveness, and other water conditions
  • Choose materials compatible with the liquid and environment
02

Compare the Pump and System Curves

The system curve rises as flow increases because pipe and equipment losses grow. The pump head curve normally falls as flow increases. Their intersection is the expected operating point for that pump in that system.

Key points 3
  • Do not compare pumps using maximum flow or shut-off head alone
  • Use the manufacturer’s curve for the actual speed, impeller diameter, and liquid
  • Check motor power and available net positive suction head across the operating range
03

Understand the Best Efficiency Point

The BEP shown in the picture is the point of best hydraulic efficiency on the pump curve. A good selection places the required duty within the manufacturer’s preferred operating range near that point, not simply anywhere the curves cross.

Key points 3
  • Operation far from BEP can increase vibration, internal recirculation, noise, and wear
  • The permitted range varies by pump design and manufacturer
  • Variable-speed control changes the pump curve and should be evaluated as part of the system
04

Avoid Oversizing and Undersizing

An oversized pump may operate too far left of its BEP, waste energy, require throttling, and experience higher mechanical stress. An undersized pump may run too far right, fail to deliver the required head, overload the motor, or face cavitation risk.

Key points 3
  • Oversizing can increase throttling losses, stress, noise, and operating cost
  • Undersizing can prevent the system from reaching its required duty
  • Select within the manufacturer’s preferred operating range wherever practical
05

Complete the Final Checks

After identifying a hydraulically suitable pump, confirm suction conditions, power supply, motor rating, controls, materials, seals, installation dimensions, noise, maintenance access, spares, and lifecycle cost.

Key points 3
  • Verify inlet conditions, power supply, controls, and motor rating
  • Confirm materials, seals, dimensions, environment, and maintenance access
  • Consider spare-parts support, energy use, and lifecycle cost before purchase