The absolute roughness is a measure of the roughness of the inside of a flowing pipe. It is used in conjunction with the inside diameter to calculate the Friction Factor using a Moody Diagram, the Reynolds Number and the Darcy-Weisbach Equation
Common values for the absolute roughness are listed below.
| Type of Pipe | Absolute Roughness ( |
Absolute Roughness ( |
|---|---|---|
| Drawn tubing (glass, brass, plastic) | 0.000005 | 0.00006 |
| Commercial steel or wrought iron (new) | 0.00015 | 0.0018 |
| Commercial steel or wrought iron (existing) | 0.0005 | 0.006 |
| Cast iron (asphalt dipped) | 0.0004 | 0.0048 |
| Galvanized iron | 0.0005 | 0.006 |
| Cast iron (uncoated) | 0.00085 | 0.0102 |
| Wood stave | 0.0006 to 0.0003 | 0.0072 to 0.0036 |
| Concrete | 0.001 to 0.01 | 0.012 to 0.12 |
| Riveted steel | 0.003 to 0.03 | 0.036 to 0.36 |
