Absolute roughness ε for common pipe and duct materials. Enter diameter and Re to compute ε/D and friction factor.
| Material | Condition | ε min (mm) | ε max (mm) | ε/D min | ε/D max | f (Darcy) | Category |
|---|---|---|---|---|---|---|---|
| Drawn copper / brass | New, commercially smooth | 0.0015 | 0.0030 | 1.50e-5 | 3.00e-5 | 0.0180 | Metal |
| Stainless steel | New, electropolished | 0.0005 | 0.0020 | 5.00e-6 | 2.00e-5 | 0.0179 | Metal |
| Stainless steel | New, standard finish | 0.0020 | 0.0100 | 2.00e-5 | 1.00e-4 | 0.0182 | Metal |
| Carbon steel | New, commercial | 0.0400 | 0.0600 | 4.00e-4 | 6.00e-4 | 0.0204 | Metal |
| Carbon steel | Light rust | 0.1000 | 0.2000 | 1.00e-3 | 2.00e-3 | 0.0239 | Metal |
| Carbon steel | General rust | 0.2000 | 0.5000 | 2.00e-3 | 5.00e-3 | 0.0288 | Metal |
| Carbon steel | Heavy rust / encrusted | 0.5000 | 3.0000 | 5.00e-3 | 3.00e-2 | 0.0469 | Metal |
| Cast iron | New, uncoated | 0.2500 | 0.8000 | 2.50e-3 | 8.00e-3 | 0.0320 | Metal |
| Cast iron | Bitumen-coated | 0.1000 | 0.3000 | 1.00e-3 | 3.00e-3 | 0.0253 | Metal |
| Cast iron | Tuberculated | 1.0000 | 3.0000 | 1.00e-2 | 3.00e-2 | 0.0493 | Metal |
| Galvanised steel | New | 0.1000 | 0.2000 | 1.00e-3 | 2.00e-3 | 0.0239 | Metal |
| Galvanised steel | Used / aged | 0.2000 | 0.4000 | 2.00e-3 | 4.00e-3 | 0.0277 | Metal |
| Wrought iron | New | 0.0450 | 0.0900 | 4.50e-4 | 9.00e-4 | 0.0211 | Metal |
| Aluminium (drawn) | New | 0.0010 | 0.0020 | 1.00e-5 | 2.00e-5 | 0.0180 | Metal |
| PVC / CPVC | New | 0.0015 | 0.0070 | 1.50e-5 | 7.00e-5 | 0.0181 | Plastic |
| Polyethylene (PE/HDPE) | New | 0.0015 | 0.0070 | 1.50e-5 | 7.00e-5 | 0.0181 | Plastic |
| GRP / FRP | New, filament wound | 0.0100 | 0.0500 | 1.00e-4 | 5.00e-4 | 0.0195 | Plastic |
| Cement-lined steel | New | 0.2500 | 1.2500 | 2.50e-3 | 1.25e-2 | 0.0354 | Concrete/Lined |
| Concrete (smooth) | Cast in steel forms | 0.0250 | 0.2000 | 2.50e-4 | 2.00e-3 | 0.0228 | Concrete/Lined |
| Concrete (rough) | Rough wood form | 0.5000 | 1.8000 | 5.00e-3 | 1.80e-2 | 0.0406 | Concrete/Lined |
| Prestressed concrete | New | 0.1000 | 0.6000 | 1.00e-3 | 6.00e-3 | 0.0288 | Concrete/Lined |
| Galvanised ductwork | Spiral / seamed | 0.0900 | 0.1500 | 9.00e-4 | 1.50e-3 | 0.0230 | Ductwork |
| Flexible duct | Fully extended | 0.9000 | 2.4000 | 9.00e-3 | 2.40e-2 | 0.0459 | Ductwork |
| Flexible duct | Compressed 10% | 3.0000 | 9.0000 | 3.00e-2 | 9.00e-2 | 0.0784 | Ductwork |
| Stainless steel duct | New | 0.0020 | 0.0100 | 2.00e-5 | 1.00e-4 | 0.0182 | Ductwork |
| Ductile iron (DI) | New | 0.0250 | 0.0500 | 2.50e-4 | 5.00e-4 | 0.0199 | Water Mains |
| Ductile iron (DI) | Cement mortar lined | 0.0250 | 0.1000 | 2.50e-4 | 1.00e-3 | 0.0209 | Water Mains |
| AC (asbestos cement) | New | 0.0250 | 0.0300 | 2.50e-4 | 3.00e-4 | 0.0194 | Water Mains |
| HDPE water main | New | 0.0070 | 0.0150 | 7.00e-5 | 1.50e-4 | 0.0185 | Water Mains |
29 of 29 entries shown.
Absolute roughness ε is the mean height of surface irregularities. It is a property of the pipe surface, not the fluid.
Relative roughness ε/D is dimensionless and enters the Colebrook-White equation. It decreases as pipe diameter increases.
Friction factor f shown is the Darcy-Weisbach friction factor, calculated via the Swamee-Jain approximation at the midpoint roughness. For Re < 2 300 laminar: f = 64/Re.
Effect of aging: Biological growth, corrosion, and scale deposition can increase effective roughness by one to two orders of magnitude over the service life.
References: Moody (1944), Colebrook & White (1937), ASHRAE Handbook of Fundamentals, Crane TP-410, White — Fluid Mechanics.