APPENDIX C
HAZEN-WILLIAMS HEADLOSS EQUATION
The Hazen-Williams equation may be expressed as follows:
= 10.7
Where = headloss due to friction, m
Q = flow rate, m3/s
C = friction coefficient, non-dimensional
L = length of pipe, m
D = diameter of pipe, m
The friction coefficient may be found in Table C-1 on the next page. Standard pipe diameters may be found in Tables C-2 and C-3.
TABLE C-1
Hazen-Williams Friction Coefficients (C) for Non-Aggressive water*
______
Concrete pipe, centrifugally spun
New140
5 y old130
10 y old100
20 y old80
Ductile iron pipe (DIP)
Lined
10-40 y old125-140
Unlined
5 y old, > 600 mm130
5 y old, 75 to 600 mm120
20 y old100
30 y old80
severely tuberculated40
FRP 120 - 150
(higher C for larger diameter)
Plastic (PVC)120-150
(higher C for larger diameter)
Steel, new, unlined140
Steel 10 y old, lined100
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* Precipitates from softened water can lower C from 140 to 120 in as short a period as 6 months. Slime build up over a 5 y period can lower C from 140 to 100.
TABLE C-2
Pipe diameters for
Mortar Lined Ductile Iron Pipe Sizes in SI and U.S. Customary Units
______
SI, nominalSI, IDU.S. NominalU.S. ID
mmmminchesinches
______
758233.22
10010244.04
15015566.10
20020888.21
2502591010.2
3003121212.3
3503631414.3
4004151616.3
4504681818.4
5005212020.5
6006272424.7
7507813030.7
9009373636.9
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TABLE C-3
Sewer Pipe Sizes in SI and U.S. Customary Units
______
SI, nominalSI, IDU.S. Nominal
mmmminches
______
100101.64
150152.46
200203.28
250254.010
300304.812
350355.614
400406.416
450457.218
500508.020
600609.624
750762.030
900914.436
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