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HDPE pipe — Darcy-Weisbach headloss

This page covers headloss calculation for HDPE pipe using the Darcy-Weisbach equation — the canonical pairing for Trenchless install, gas, slip-line rehab.

Pipe parameters — HDPE

Hazen-Williams C-factor (new)
150
Hazen-Williams C-factor (aged)
145
Absolute roughness (ε)
5e-06 ft
Typical uses
Trenchless install, gas, slip-line rehab

Darcy-Weisbach method

Universal — works for any fluid + any flow regime (laminar, transitional, turbulent).

Formula

h_f = f · (L/D) · (V² / 2g)

Limitations

Requires the friction factor f, which depends on Reynolds number and relative roughness — typically evaluated via the Colebrook equation or Moody chart.