Absolute pipe roughness table (ε)
Reference values of absolute roughness ε (mm) for the Colebrook-White and Darcy-Weisbach equations, covering 31 pipe materials in new and aged condition — the same dataset the LOGOS hydraulic calculators use.
What absolute roughness is
Absolute roughness ε is the average height of the internal surface irregularities of a pipe, expressed in millimeters. It is a property of the material and of its condition: a carbon steel pipe leaves the mill at ε ≈ 0.045 mm and can exceed 1 mm after years of corrosion and scaling.
In head-loss calculations, ε never acts alone — what enters the friction model is the relative roughness ε/D, the ratio between roughness and internal diameter. The same ε that is negligible in a 400 mm line dominates the friction factor in a 25 mm one.
Where it enters the calculation
The friction factor f of the Darcy-Weisbach equation, h_f = f · (L/D) · (v²/2g), comes from the Colebrook-White equation in turbulent flow:
1/√f = −2·log₁₀( ε/(3.7·D) + 2.51/(Re·√f) )
The first term inside the logarithm carries ε/D. At high Reynolds numbers (fully rough regime) the second term vanishes and f depends only on ε/D — which is why picking the right roughness matters more in large, fast systems than any refinement of the Reynolds number.
How to pick a value from the table
- Typical (ε typ) — use it as the default design value for the material in the stated condition.
- Minimum (ε min) — optimistic bound; useful to check the sensitivity of the result, never for sizing.
- Maximum (ε max) — conservative bound; appropriate when the fluid is aggressive, the water is untreated, or the line will operate for decades without cleaning.
A robust practice for pumped systems: size the pump head with aged-pipe roughness (the system curve gets steeper over time) and verify the maximum flow — motor loading, NPSH, valve authority — with new-pipe roughness.
Absolute roughness ε by pipe material (mm)
| Category | Material | ε min (mm) | ε typical (mm) | ε max (mm) | Notes |
|---|---|---|---|---|---|
| Steels | New carbon steel (seamless) | 0.025 | 0.045 | 0.09 | A106, A53 — standard recommendation |
| Steels | Welded carbon steel | 0.04 | 0.06 | 0.1 | Helical/longitudinal seam |
| Steels | Carbon steel, in service 1–2 years | 0.15 | 0.2 | 0.25 | Slight internal rusting |
| Steels | Carbon steel, in service >5 years | 0.5 | 1 | 2 | Severe rusting, scaling |
| Steels | Carbon steel, internal epoxy lining | 0.04 | 0.06 | 0.1 | AWWA C210 / C213 |
| Steels | New galvanized steel | 0.09 | 0.15 | 0.25 | Hot-dip galvanized |
| Steels | Used galvanized steel | 0.25 | 0.4 | 0.6 | After years in service |
| Steels | Stainless steel (304/316) | 0.015 | 0.025 | 0.05 | Standard polish |
| Steels | Polished sanitary stainless steel | 0.0008 | 0.0015 | 0.003 | Ra ≤ 0.8 µm — food/pharma |
| Irons | New cast iron | 0.25 | 0.4 | 0.6 | — |
| Irons | Asphalt-lined cast iron | 0.1 | 0.15 | 0.22 | — |
| Irons | Used cast iron | 0.8 | 1.5 | 3 | Tuberculation |
| Irons | New ductile iron (cement-lined) | 0.05 | 0.08 | 0.15 | EN 545 / AWWA C151 |
| Irons | Used ductile iron | 0.15 | 0.25 | 0.5 | — |
| Plastics | Rigid PVC (PN 6 to PN 25) | 0.0015 | 0.005 | 0.01 | NBR 5648 / 5688 |
| Plastics | CPVC | 0.0015 | 0.005 | 0.01 | — |
| Plastics | New HDPE (PE 80, PE 100) | 0.0015 | 0.007 | 0.02 | ISO 4427 |
| Plastics | Used HDPE (>10 years) | 0.02 | 0.05 | 0.1 | Little internal degradation |
| Plastics | PEX (cross-linked polyethylene) | 0.0015 | 0.007 | 0.02 | — |
| Plastics | PPR (polypropylene random) | 0.005 | 0.01 | 0.02 | — |
| Plastics | FRP / GRP | 0.02 | 0.05 | 0.1 | Varies with the process |
| Copper | New drawn copper | 0.0015 | 0.003 | 0.01 | Types K/L/M |
| Copper | Used copper | 0.005 | 0.01 | 0.02 | — |
| Copper | Brass | 0.0015 | 0.0025 | 0.005 | — |
| Concrete | Smooth concrete (steel forms) | 0.3 | 0.5 | 1 | Good finish |
| Concrete | Ordinary concrete | 1 | 2.5 | 5 | Average finish |
| Concrete | Rough concrete | 3 | 6 | 10 | Poor finish |
| Others | Planed wood | 0.2 | 0.5 | 1 | — |
| Others | Glass / acrylic | 0.0001 | 0.001 | 0.003 | Hydraulically smooth |
| Others | Smooth rubber | 0.01 | 0.015 | 0.03 | — |
| Others | Corrugated flexible hose | 1 | 3 | 5 | Spiral-wound hose |
Same dataset used by the LOGOS head-loss calculators (Colebrook-White). Values in millimeters.
Standards & methods
- Colebrook-White
- Darcy-Weisbach
- EPANET 2.2
- AWWA C210/C213
- ISO 4427
- NBR 5648
Frequently asked questions
What roughness should I use for new carbon steel pipe?
For new seamless carbon steel (A106/A53), use ε = 0.045 mm as the standard design value. The plausible range is 0.025–0.09 mm; welded pipe runs slightly higher (0.06 mm typical).
What is the absolute roughness of PVC pipe?
Rigid PVC is hydraulically smooth: ε = 0.005 mm typical, range 0.0015–0.01 mm. In practice the friction factor of PVC at usual Reynolds numbers is close to the smooth-pipe limit, so small variations of ε barely change the result.
How much does aging change roughness?
Dramatically — it is the largest uncertainty in head-loss calculations. Carbon steel goes from 0.045 mm new to ~0.2 mm after 1–2 years and 0.5–2 mm after 5+ years of corrosion and scaling. Designing a pump with new-pipe roughness for a 20-year system underestimates friction losses.
Absolute or relative roughness — which one goes into Colebrook-White?
The equation uses the relative roughness ε/D (dimensionless): divide the ε from this table (mm) by the internal diameter of the pipe in the same unit. A 0.045 mm roughness in a 100 mm pipe gives ε/D = 0.00045.
Does roughness matter in laminar flow?
No. In laminar flow (Re < 2300) the friction factor is f = 64/Re and does not depend on roughness at all. Roughness only enters in the transitional and turbulent regimes.