Sump pump calculator
Inflow, vertical lift, discharge pipe length, safety factor and efficiency: you get minimum pump flow, total dynamic head and estimated power.
Minimum pump flow
60 l/min
- Minimum pump flow60 l/min
- Total dynamic head4 m
- Estimated input power0.1 kW
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How it's calculated (visible formula)
Q = inflow × safety factor; head = lift + 0.1 × pipe length; P = ρ·g·Q·H ÷ efficiency
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
How to calculate it, step by step
- Time how fast water rises in the pit for one minute with the pump off.
- Apply a safety factor (1.5 typical).
- Measure the vertical lift to the discharge point.
- Add pipe friction (≈ 1 ft per 10 ft of pipe).
- Pick a pump that delivers that flow at that head on its curve.
Worked example: 10.6 gpm inflow, 10 ft lift, 33 ft of pipe
- Q = 10.6 × 1.5 ≈ 16 gpm
- Head ≈ 10 + 3.3 = 13 ft
- Power ≈ 0.1 kW
→ Pick a pump rated 16 gpm at 13 ft (a ⅓ hp unit is ample).
Common mistakes
- Sizing from the 0 ft catalog flow.
- No check valve.
- Pit too small, so the pump short-cycles.
Pro tips
- Install a check valve so water doesn't drain back.
- Use a tether-free float switch and test it each season.
- Add a high-water alarm in finished basements.
- Discharge well away from the foundation.
From calculation to quote
Add labour, overhead and your margin, and generate the professional PDF.
FAQs
- How do I measure inflow?
- Time how fast water rises in the pit for one minute with the pump off.
- What is total dynamic head?
- Vertical lift plus friction losses in pipe and fittings.
- Do I need a backup?
- For finished basements, a battery backup or second pump is strongly advised.
- Submersible or pedestal?
- Submersibles are quieter; pedestals are easier to service.
- How often should I test a sump pump?
- At least yearly — fill the pit and watch it cycle.
- What size sump basin?
- Large enough for cycles of a few minutes — 18 in wide × 24 in deep is common.
Sources and standards
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.