Hazen-Williams Coefficient

Hazen-Williams coefficient, abbreviated as C, also called Hazen-Williams friction coefficient, a dimensionless number, is used in the Hazen-Williams Equation.  The lower the coefficient, the smoother the pipe is.  The higher the coefficient, the less fluid flow is restricted.  By using pipe materials with improved flow characteristics, energy costs for pumping can be reduced or smaller pipes can be used.

Note that the Hazen-Williams Coefficient is '''not''' the same as the Darcy-Weibach-Colebrook friction factor, f.  These are not in any way related to each other.

 

Hazen-Williams coefficient formulas

\(\large{ C = \frac {v}{ 1.318 \; r_h^{0.63}  \; m^{0.54} }  }\)	(mean flow velocity)
\(\large{ C = \frac {Q}{ 0.285 \; d^{2.63}  \; m^{0.54} }  }\)	(flow flow rate)

Where:

Units	English	Metric
\(\large{ C }\) = Hazen-Williams Coefficient, see below for values	\(\large{ dimensionless }\)
\(\large{ Q }\) = flow rate	\(\large{\frac{ft^3}{sec}}\)	\(\large{\frac{m^3}{s}}\)
\(\large{ m }\) = hydraulic grade line slope	\(\large{ dimensionless }\)
\(\large{ r_h }\) = hydraulic radius	\(\large{ ft }\)	\(\large{ m }\)
\(\large{ v }\) = mean flow velocity	\(\large{\frac{ft}{sec}}\)	\(\large{\frac{m}{s}}\)
\(\large{ d }\) = pipe inside diameter	\(\large{ in }\)	\(\large{ mm }\)

 

Hazen-Williams Coefficient Table

Material	Hazen Williams Coefficient
Aluminum	130 - 150
Asbestos Cement	120 - 150
Asphalt-lined iron or steel	140
Brass	130
Cast Iron, cement lined	140
Cast Iron, coated	110 - 140
Cast Iron, new unlined	130
Cast Iron, old unlined	40 - 120
Cast Iron, uncoated	100 - 140
Cast Iron, 10 years old	107 - 113
Cast Iron, 20 years old	89 - 100
Cast Iron, 30 years old	75 - 90
Cast Iron, 40 years old	64 - 83
Cement lining	140
Concrete	100 - 140
Concrete, old	100 - 110
Copper	130 - 140
Corrugated Metal Pipe	60
Corrugated Steel	60
Deteriorated old pipes	60 - 80
Ductile Iron	120 - 145
Fiberglass	150
Galvanized Iron	100 - 120
Glass	130
Lead	130
Polyethylene	140
PVC, PE, GRP	120 - 150
Steel, new unlined	120
Steel, 15 years	200
Steel, riveted joints	95 - 110
Steel, welded joints	100 - 140
Steel, welded joints, lined	110 - 140
Steel, welded or steamless	100 - 120
Tin	130
Wood Stave	110