Surface Roughness ε (for water pipes) Material mm in Corrugated plastic pipes (apparent roughness) 3.5 0.14[7] Mature foul sewers 3.0 0.12[7] Steel water mains with general tuberculations 1.2 0.047[7] Riveted Steel 0.9–9.0 0.035–0.35 Concrete (heavy brush asphalts or eroded by sharp material), Brick 0.5 0.02[7][8] Concrete 0.3–3.0 0.012–0.12 Wood Stave 0.2–0.9 5–23 Galvanized metals (normal finish), Cast iron (coated and uncoated) 0.15–0.26 0.006–0.010[7] Asphalted Cast Iron 0.12 0.0048 Concrete (new, or fairly new, smooth) 0.1 0.004[7] Steel Pipes, Galvanized metals (smooth finish), Concrete (new, unusually smooth, with smooth joints), Asbestos cement, Flexible straight rubber pipe (with smooth bore) 0.025–0.045 0.001–0.0018[7] Commercial or Welded Steel, Wrought Iron 0.045 0.0018 PVC, Brass, Copper, Glass, other drawn tubing 0.0015–0.0025 0.00006–0.0001[7][8]