Gravity Supply Pipe Calculator
Hazen-Williams friction loss, net head and velocity check — gravity-fed village line.
Gravity schemes live and die on friction: the source is 40 m up, but 1 km of undersized pipe can eat it all. Check residual head at the standpost — 7–10 m minimum keeps taps usable.
Gravity-fed village line: friction loss scales with the 4.87th power of diameter — one pipe size up typically cuts the loss by 60%. For hydro, lost head is lost power forever; for pumping, it's a permanently bigger electricity bill. Buy diameter once instead.
Engineering estimate from published standards and typical equipment data. Site conditions, equipment datasheets and measured data govern the real result — confirm with a qualified engineer.
Use the free Gravity Supply Pipe Calculator online — Hazen-Williams friction loss, net head and velocity check — gravity-fed village line. Runs instantly in your browser: no signup, no upload, mobile-friendly.
About Gravity Supply Pipe Calculator
Gravity schemes live and die on friction: the source is 40 m up, but 1 km of undersized pipe can eat it all. Check residual head at the standpost — 7–10 m minimum keeps taps usable.
How to use Gravity Supply Pipe Calculator
- 1Enter pipe length, inner diameter and flow.
- 2Pick the pipe material.
- 3Read friction loss, remaining head and the velocity verdict.
Why use Gravity Supply Pipe Calculator?
- ✓Hazen-Williams with material-correct roughness coefficients
- ✓Velocity check warns against erosion and hammer territory
- ✓Net-head output feeds straight into hydro/pump decisions
- ✓The diameter lesson: one size up cuts loss ~60%
Frequently asked questions
How much head do I lose to pipe friction?+
Hazen-Williams: loss scales with length, flow^1.85, and — brutally — diameter^−4.87. 200 m of 110 mm HDPE at 8 L/s loses ~3 m; the same flow in 90 mm loses ~7.5 m. For hydro that's power gone forever; for pumping it's a permanently fatter bill. The tool runs your exact case.
What pipe velocity is acceptable?+
Design comfort: 1–3 m/s. Below 1, you've overspent on diameter (and sediment may settle); above 3, friction soars, erosion accelerates, and water hammer on valve closure becomes violent. The velocity readout here flags both ends.
Is bigger pipe worth the extra cost?+
Almost always over the system's life: the next standard diameter typically cuts friction loss ~60%, repaying its premium in saved pumping energy within a few years — or in permanently higher hydro output. Buy diameter once; buy losses forever.
Which C value should I use?+
Material and age: new HDPE/PVC ≈150, new steel ≈130, old rusted steel ≈100, concrete ≈120. Aging matters — a 20-year-old steel line at C=100 loses nearly twice what its installation calculations promised. When relining or replacing, this delta IS the business case.
Embed Gravity Supply Pipe Calculator on your website
Want Gravity Supply Pipe Calculatoron your own site? Paste this snippet into any HTML page — it's free, with no API key or sign-up. The tool loads in an iframe and keeps working exactly as it does here.
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