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Sump Inflow and Pump Curve Calculator

Measure basin inflow and compare actual pump curves with static and friction head; identify operating points without extrapolating a horsepower size.

Use this result well

Inputs that matter
Effective cylindrical basin diameter (in), Observed water-level rise (in), Observation interval (minutes), Reviewed design multiplier, and 10 more
Output to expect
Sump inflow from a measured rise, Actual pump curves and system head
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Sump inflow from a measured rise

Estimate inflow from a measured level rise while the pump is off in a cylindrical basin with known net cross-sectional area. Measure only when the site can be observed without risking overflow. Exclude displaced volume with the entered effective diameter or use an independently measured volume.

Volume US gallons = π × effective diameter² / 4 × rise inches / 231; inflow US gpm = volume / elapsed minutes.

Actual pump curves and system head

Find operating points where entered pump curves intersect a steady full-pipe system curve. Use at least two documented points per exact pump/impeller/speed, with increasing flow and nonincreasing head. Compare only within the entered curve range; no horsepower catalog or curve extrapolation is used.

Operating point satisfies pump head(Q) = static + residual + pipe/local loss(Q). Pump head is linearly interpolated between documented points.

Updated: September 2026

Example Scenarios

Try this example to see the calculation, then enter actual documented values and preserve the measurement conditions. A failed or unresolved comparison is part of the record.

→ 2.203195 US gpm observed inflow

Try this example to see the calculation, then enter actual documented values and preserve the measurement conditions. A failed or unresolved comparison is part of the record.

→ 2 pump(s) meet entered inflow · 2 operating point(s) located

FAQ

Estimate inflow from a measured level rise while the pump is off in a cylindrical basin with known net cross-sectional area. Measure only when the site can be observed without risking overflow. Exclude displaced volume with the entered effective diameter or use an independently measured volume. Find operating points where entered pump curves intersect a steady full-pipe system curve. Use at least two documented points per exact pump/impeller/speed, with increasing flow and nonincreasing head. Compare only within the entered curve range; no horsepower catalog or curve extrapolation is used.

Use the exact equipment data, measurement point, operating conditions and units described in the selected mode. Record source documents, dates and unresolved conditions in Sources and assumptions. Built-in examples illustrate arithmetic; they are not manufacturer ratings or approved designs.

Use Save planning case for an explicit local history entry. Copy MD keeps current inputs and notes; Download CSV exports the result breakdown. Export portable copies before clearing storage and save a separate case after changing equipment, conditions or measurements.

About Sump Inflow and Pump Curve Calculator

Estimate inflow from a measured level rise while the pump is off in a cylindrical basin with known net cross-sectional area. Measure only when the site can be observed without risking overflow. Exclude displaced volume with the entered effective diameter or use an independently measured volume. Find operating points where entered pump curves intersect a steady full-pipe system curve. Use at least two documented points per exact pump/impeller/speed, with increasing flow and nonincreasing head. Compare only within the entered curve range; no horsepower catalog or curve extrapolation is used.