Roughness Values-Hazen-Williams Equation
Commonly used roughness values for different materials are:
Hazen-Williams Roughness Coefficients (C)
| Pipe Material | C |
|---|---|
| Asbestos Cement | 140 |
| Brass | 130-140 |
| Brick Sewer | 100 |
| Cast iron | |
| New, unlined | 130 |
| 10 yr. Old | 107-113 |
| 20 yr. Old | 89-100 |
| 30 yr. Old | 75-90 |
| 40 yr. Old | 64-83 |
| Concrete or concrete lined | |
| Steel forms | 140 |
| Wooden forms | 120 |
| Centrifugally spun | 135 |
| Copper | 130-140 |
| Galvanized iron | 120 |
| Glass | 140 |
| Lead | 130-140 |
| Plastic | 140-150 |
| Steel | |
| Coal-tar enamel, lined | 145-150 |
| New unlined | 140-150 |
| Riveted | 110 |
| Tin | 130 |
| Vitrified clay (good condition) 110-140 | 110-140 |
| Wood stave (average condition) | 120 |