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Hazen Williams Coefficients

Reference data and engineering information about hazen williams coefficients for miscellaneous applications.

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Overview

Engineering reference data for Hazen Williams Coefficients in miscellaneous.

Key Formulas

Unit Conversion

y=x⋅ky = x \cdot k

Multiply by conversion factor.

Linear Interpolation

y=y1+(x−x1)(y2−y1)x2−x1y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}

Estimate between two known points.

Percentage

p=partwhole×100%p = \frac{\text{part}}{\text{whole}} \times 100\%

Part as fraction of whole.

Variables

Symbol Description Unit
xx Input value —
yy Output value —
kk Conversion factor —

Hazen-Williams Coefficients Table

The Hazen-Williams coefficient (C) represents the relative smoothness of a pipe's interior surface. Higher values indicate smoother surfaces with less friction loss. These coefficients are empirical values commonly used in hydraulic engineering for water flow calculations.

Key Observations

  • Pipe aging significantly affects coefficients: Cast-iron pipe C values decrease from 130 (new) to 64–83 (40 years old) due to corrosion and tuberculation
  • Lining restores or improves coefficients: Cement-lined and bituminous-lined cast-iron pipes achieve C = 140, matching new smooth pipes
  • Plastic and modern materials (PVC, CPVC, FRP) consistently show high coefficients (150) due to their smooth interior surfaces
  • Corrugated metal has the lowest coefficient (60) due to the rough, wavy interior surface
  • Ranges indicate variability based on manufacturing conditions, age, and installation quality

References