What this tool does
Estimate straight-pipe and optional minor loss at a known flow, actual internal diameter and length. The two modes make the method and its limits visible.
When to use it
Use Hazen–Williams for a conventional empirical water estimate with an appropriate C value. Use Darcy–Weisbach when Reynolds number, water temperature and roughness need to be represented explicitly.
Inputs and supported units
Each labelled field explains the quantity it expects. Unit-system changes convert existing numeric entries once and keep calculations on a single SI internal basis. Supported shared units include L/min and GPM, metres and feet, kPa and psi, millimetres and inches, kW and hp, and °C and °F as relevant.
Calculation or decision method
Laminar flow uses f = 64/Re. Turbulent flow uses the explicit Swamee–Jain approximation. Transitional results are identified rather than presented as certain.
How to interpret the result
Read the primary result with the supporting breakdown and warning. A plausible number is not evidence that every input, operating case or design constraint has been included.
Worked example
For 120 L/min through 50 mm ID pipe over 80 m, Hazen–Williams with C = 140 estimates about 1.97 m of major head loss. A combined minor-loss K of 2 adds about 0.11 m. Actual ID and fittings can materially change the result.
Assumptions
Water only; steady full-pipe flow; a circular pipe; uniform internal diameter; roughness and C values selected by the user.
Limitations
Hazen–Williams is empirical and does not model viscosity. The explicit Darcy approximation is not a substitute for detailed transient or network analysis.
Sources
- U.S. Army Corps of Engineers — EM 1110-1-4008
- U.S. EPA — Storm Water Management Model User’s Manual 5.2
- NIST — Thermophysical Properties of Fluid Systems