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Pool Plumbing Head Loss

Hazen-Williams friction loss, net head and velocity check — pool suction/return.

Pool pumps fight their own plumbing — undersized suction lines cause most 'weak pump' complaints. Total dynamic head from this estimate picks the right (smaller) pump at the right flow.

2.7 m (9% of head)
Friction head loss
Net head remaining27.3 m
Flow velocity2.57 m/s (target 1–3)
Hazen-Williams C150 (HDPE / PVC (smooth))
Design rulekeep penstock loss ≤ 10% of gross head

Pool suction/return: 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.

Sources: Hazen-Williams head-loss formula (SI form)

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 Pool Plumbing Head Loss online — Hazen-Williams friction loss, net head and velocity check — pool suction/return. Runs instantly in your browser: no signup, no upload, mobile-friendly.

About Pool Plumbing Head Loss

Pool pumps fight their own plumbing — undersized suction lines cause most 'weak pump' complaints. Total dynamic head from this estimate picks the right (smaller) pump at the right flow.

How to use Pool Plumbing Head Loss

  1. 1Enter pipe length, inner diameter and flow.
  2. 2Pick the pipe material.
  3. 3Read friction loss, remaining head and the velocity verdict.

Why use Pool Plumbing Head Loss?

  • 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.

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