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Hazen-Williams — Pipe Velocity and Head Loss

Related: Topic 4: Pipe Flow — Darcy-Weisbach, minor losses, and exam traps
Related: Formula quick-reference index

For a full-flowing water pipe, enter the diameter, Hazen-Williams C-factor, and energy slope to get velocity, discharge, and friction head loss. Water only — for other fluids use Darcy-Weisbach.

V = k · C · R^0.63 · S^0.54

k	1.318 for US units (V in ft/s), 0.849 for SI (V in m/s)
C	Hazen-Williams roughness (≈ 150 new PVC, 130 new steel, 100 old cast iron)
R = D/4	hydraulic radius for a full circular pipe
S = h_f/L	slope of the energy grade line

Head loss over a length L is simply h_f = S·L.

Unit system Pipe diameter D (ft) C-factor Energy slope S (ft/ft) Pipe length L (ft)

For study and checking only. These calculators run entirely in your browser — nothing is sent anywhere. They are meant to verify your hand calculations while you study; on the exam you will work by hand with the NCEES reference handbook.