Calculate pipe head loss and pressure drop using the Darcy-Weisbach equation with Colebrook iterative friction factor. Includes major losses (pipe friction), minor losses (fittings K-factors), Reynolds number, flow regime, and pump head requirement.
Internal (bore) diameter of the pipe — not the outer diameter.
Total length of the straight pipe run (not including fittings).
Volumetric flow rate in litres per second.
Absolute surface roughness. Drawn steel/copper: 0.046; galvanised: 0.15; cast iron: 0.26. See table below.
Water at 20°C: 998 kg/m³. Water at 60°C: 983 kg/m³. Light oil: ~850 kg/m³.
1 cSt = 10⁻⁶ m²/s. Water at 20°C: 1.0 cSt. Water at 60°C: 0.47 cSt. SAE 30 oil: ~110 cSt.
Sum of K-factors for all fittings/valves. See the K-factor table. Zero to ignore minor losses.