Flow • Velocity • Pipe loss
Compare delivery-pipe sizes at the same flow.
Compare how two or three actual internal pipe diameters change velocity and delivery-pipe friction loss at the same water flow, length, roughness, and fittings K.
Enter actual internal diameter—not nominal pipe size or outside diameter.Step 3
Comparison result
Enter two actual internal diameters to compare pipe loss.
At the same entered flow, length, roughness, and fittings K, internal diameter changes velocity and calculated delivery-pipe loss. This result covers pipe and entered fitting losses only—not elevation, required outlet pressure, suction losses, or total dynamic head.
This is not total dynamic head, pump selection, pipe-pressure-class verification, or final system design. Verify actual pipe data, operating flow, fittings, elevation, required pressure, manufacturer limits, applicable standards, and qualified design requirements.
Method and fixed assumptions
Darcy-Weisbach calculates straight-pipe loss. Reynolds number uses laminar handling at Re ≤ 2300, no friction result from 2300 to 4000, and iterative Colebrook-White handling at Re ≥ 4000. Clean water is fixed at 20 °C, density 998.2 kg/m³, kinematic viscosity 1.004 × 10⁻⁶ m²/s, and g 9.80665 m/s².
Roughness, fittings K, and actual diameter
Roughness and fitting coefficients are user-entered assumptions and may change with material, condition, deposits, geometry, and manufacturer. Actual internal diameter must be verified from the pipe manufacturer's data. Nominal size is not converted because internal diameter varies by pipe specification.
How to interpret equal-flow comparison
Actual operating flow can change when the pipe and pump system changes. Holding flow constant isolates the pipe-size effect; it is not a predicted pump operating point. Verify permissible velocity, pressure, pipe class, pump duty, and installation requirements separately.