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Sump Pump Size Calculator

Who it's for: Plumbing contractors, service technicians, and homeowners evaluating sump replacement.

Sump Pump Size Calculator helps plumbing contractors, service technicians, and homeowners evaluating sump replacement. turn estimated inflow (gpm), safety factor (%), total dynamic head (ft) into required planning flow (gpm), suggested hp class, pump-curve verification note without hiding the assumptions behind the result.

Calculator Inputs

Next Steps

  • Confirm inflow assumptions from site observations or historical pump-cycle data when possible.
  • Use conservative head estimates that include vertical lift and friction losses.
  • Always verify final pump selection on manufacturer pump curves at your actual duty point.

Worked Example

Example: enter realistic values for estimated inflow (gpm), safety factor (%), review required planning flow (gpm), suggested hp class, then compare the result with field conditions before using it for a material or equipment decision.

How This Calculator Works

Scales estimated inflow by user-selected safety factor to produce required planning flow. Maps required flow to a simple HP class table for head <= 10 ft. Applies a one-class increase when dynamic head exceeds 10 ft to reflect extra pumping demand.

  • Scales estimated inflow by user-selected safety factor to produce required planning flow.
  • Maps required flow to a simple HP class table for head <= 10 ft.
  • Applies a one-class increase when dynamic head exceeds 10 ft to reflect extra pumping demand.

Common Mistakes

  • Entering estimated inflow (gpm) in the wrong unit or using an unverified field estimate.
  • Reading required planning flow (gpm) without checking the assumptions listed on the page.
  • Skipping manufacturer data, local code, or field verification when the result affects final installation.

FAQ

Required flow is inflow multiplied by the safety factor, giving a planning target above expected normal inflow.

Higher head typically reduces delivered flow, so the estimator shifts one class up when head is above a simple threshold.

No. Final model selection must be validated against manufacturer curves and project-specific head calculations.

Use a factor that matches project risk and uncertainty; too little margin can undersize, while too much can overshoot cost and cycling behavior.

When to Call a Professional

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

Related Calculators

Pipe Volume Calculator

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

Drain Slope Calculator

Calculate total vertical drop for drain runs from slope per foot so plumbing crews can set elevations quickly and avoid low-slope drainage issues.

Conclusion

Use the Sump Pump Size Calculator result to understand required planning flow (gpm), suggested hp class, pump-curve verification note from estimated inflow (gpm), safety factor (%), total dynamic head (ft). Keep the input assumptions with the result so another person can reproduce the same estimate.

About This Calculator

About this calculator: Plumbing contractors, service technicians, and homeowners evaluating sump replacement.

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

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

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