Sizing a pump correctly ensures reliable performance and efficiency. The process comes down to defining your duty point: the flow rate and the total dynamic head (TDH). With just a few calculations and checks, you can avoid undersized or oversized pumps, saving both energy and maintenance costs.

1. Define the Duty Point

Your pump’s duty point is the combination of required flow rate and head. It determines the pump curve you’ll be working with. Always start here before looking at models.

2. Estimate Flow

Flow can be estimated by fixture counts, process requirements, or system design. For example:

• Residential water system: Count fixtures and use standard fixture-unit tables.
• Industrial process: Use process flow requirements (e.g., 120 GPM cooling water).
• Replacement pump: Check existing meter data or nameplate info.

3. Calculate Total Dynamic Head (TDH)

TDH is the sum of:

• Static Lift: Vertical height the pump must push water.
• Friction Loss: Resistance from pipe length, fittings, and valves.
• Discharge Pressure: Pressure required at the system’s end use.

4. Check NPSH & Efficiency

Net Positive Suction Head (NPSH) must exceed the pump’s requirement to avoid cavitation. Also, look at pump efficiency curves — higher efficiency saves on long-term energy bills.

5. Validate Against Curve

Finally, plot your system curve against pump curves. The intersection is the operating point. Choose a pump that runs near its Best Efficiency Point (BEP). Explore options like booster pumps or submersible pumps for different applications.