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Well Pump Size Calculator

Who it's for: Well and plumbing contractors, service technicians, and estimators.

Well Pump Size Calculator helps well and plumbing contractors, service technicians, and estimators. turn desired flow rate (gpm), static and pumping water levels (ft), pressure tank cut-in/cut-out (psi) into total dynamic head (tdh), pressure head and lift head, required flow without hiding the assumptions behind the result.

Calculator Inputs

Next Steps

  • Use measured pumping water level when possible; static level alone can understate required head.
  • Friction losses vary with pipe size, fittings, and flow rate, so keep this input conservative.
  • Always confirm final selection using manufacturer pump curves at your actual duty point.

Worked Example

Example: enter realistic values for desired flow rate (gpm), static and pumping water levels (ft), review total dynamic head (tdh), pressure head and lift head, then compare the result with field conditions before using it for a material or equipment decision.

How This Calculator Works

Converts cut-out pressure to feet of head using 2.31 ft per psi for a worst-case tank-pressure target. Builds lift head from pumping water level plus elevation to the highest fixture and adds estimated friction losses. Applies a safety factor and maps resulting TDH plus flow demand to a heuristic pump HP class.

  • Converts cut-out pressure to feet of head using 2.31 ft per psi for a worst-case tank-pressure target.
  • Builds lift head from pumping water level plus elevation to the highest fixture and adds estimated friction losses.
  • Applies a safety factor and maps resulting TDH plus flow demand to a heuristic pump HP class.

Common Mistakes

  • Entering desired flow rate (gpm) in the wrong unit or using an unverified field estimate.
  • Reading total dynamic head (tdh) without checking the assumptions listed on the page.
  • Skipping manufacturer data, local code, or field verification when the result affects final installation.

FAQ

TDH is estimated from lift head, pressure head, and user-entered friction losses, then adjusted by a safety factor.

Cut-out pressure is used as a worst-case operating target so the estimate reflects higher required head conditions.

No. Final model selection requires manufacturer pump curves and verified field conditions.

High-head scenarios should be validated with detailed pump-curve analysis and often require more specific system design.

When to Call a Professional

Use a licensed plumbing professional when the Well Pump Size Calculator result affects final sizing, drainage performance, equipment selection, or local code compliance.

Related Calculators

Sump Pump Size Calculator

Estimate required sump pump flow with safety margin and suggest an initial HP class for planning checks.

Pipe Volume Calculator

Calculate pipe internal volume in gallons, liters, and cubic feet from diameter and run length for planning and flushing estimates.

Conclusion

Use the Well Pump Size Calculator result to understand total dynamic head (tdh), pressure head and lift head, required flow, suggested pump hp class from desired flow rate (gpm), static and pumping water levels (ft), pressure tank cut-in/cut-out (psi). Keep the input assumptions with the result so another person can reproduce the same estimate.

About This Calculator

About this calculator: Well and plumbing contractors, service technicians, and estimators.

Educational planning estimate. Verify final plumbing decisions against local code, product data, and site conditions.

Written by BuildCalcTools Team - Well Pump Size Calculator methodology and field-use notes.

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