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Hazen-Williams Pipe Flow Calculator

Calculate pipe flow velocity, discharge, and head loss using the Hazen-Williams formula for water supply and pressure pipe systems.

Hydraulics & Water Resources Civil engineers, water utility engineers, plumbing designers Commercial Intent: HIGH

Engineering Formulas

Hazen-Williams Equation

V = 0.849 ร— C ร— R0.63 ร— S0.54 (SI) V = 1.318 ร— C ร— R0.63 ร— S0.54 (US) Q = V ร— A
V: Flow velocity (m/s)
C: Hazen-Williams roughness coefficient
R: Hydraulic radius = d/4 for full pipe (m)
S: Head loss per meter (m/m)
Q: Flow rate (mยณ/s)
A: Cross-sectional pipe area (mยฒ)
d: Pipe internal diameter (m)

Engineering Notes

Hazen-Williams is best for water at ambient temperatures.
For non-water fluids or extreme temperatures, use Darcy-Weisbach.
C values decrease with pipe age due to corrosion and scaling.
Valid for pipe diameters from 50 mm to 2000 mm typically.

Assumptions

โ€ข Steady, uniform flow conditions
โ€ข Pipe flowing full (pressurized flow)
โ€ข Water at 60ยฐF (15.6ยฐC) typical temperature range
โ€ข Circular pipe cross-section assumed
โ€ข Hydraulic radius R = d/4 for full pipe flow

Common Mistakes

โœ• Using the wrong C value for aged pipes
โœ• Forgetting to convert diameter to meters
โœ• Using Hazen-Williams for fluids other than water
โœ• Applying Hazen-Williams outside its valid diameter range

Frequently Asked Questions

What is the Hazen-Williams equation used for?

The Hazen-Williams equation calculates flow velocity, discharge, and head loss in pressure pipes for water supply systems. It's widely used for water distribution network design, pump sizing, and pipeline sizing.

What is the Hazen-Williams coefficient C?

The Hazen-Williams coefficient C represents pipe roughness. Higher values (e.g., 150 for PVC) indicate smoother pipes with less friction loss. Lower values (e.g., 60 for corrugated metal) indicate rougher pipes with more friction loss.

What is the difference between Hazen-Williams and Darcy-Weisbach?

Hazen-Williams is empirical and simpler, best for water at typical temperatures. Darcy-Weisbach is more theoretically rigorous and applies to any fluid and temperature. Hazen-Williams is preferred for water distribution design in the US.

References & Standards

AWWA Manual M11AWWA Manual M23ISO 4427
Hazen & Williams (1905)
Original hydraulic tables for water supply
AWWA Manual M11
Steel Pipe โ€” A Guide for Design and Installation
AWWA Manual M23
PVC Pipe โ€” Design and Installation
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