Hazen Williams Water Pipe Head Loss Calculator
Find the friction head loss in a water pipe with the Hazen Williams formula, widely used for water supply, cooling water and fire water networks.
- hf = 10.67 × L × Q1.852 ÷ (C1.852 × D4.87)
- = 8.905 m with Q in m³/s, D and L in m
Hazen Williams Formula (SI)
hf is the head loss in metres of water, L the pipe length in m, Q the flow in m³/s, D the inside diameter in m and C the Hazen Williams roughness coefficient (higher is smoother). The formula is empirical and valid for water at normal temperatures in turbulent flow; for other liquids use the Darcy Weisbach pipe pressure drop calculator.
Worked example
100 m³/h of water through 500 m of 6" steel pipe (154.1 mm, C = 120) loses about 8.9 m of head (0.87 bar), at 1.49 m/s.
Frequently Asked Questions
When should I use Hazen Williams instead of Darcy Weisbach?
For water in turbulent flow at normal temperature, where it is simple and widely used in codes. For other fluids or laminar flow, use Darcy Weisbach.
What C value should I use?
From the pipe material and age: about 150 for plastic, 130 to 140 for new lined pipe and 100 to 120 for steel depending on condition, or as the design code specifies.
Is the result in head or pressure?
Head in metres of water; multiply by ρg to get pressure (about 0.098 bar per metre).
Learn more on the blog
What factors affect the stability of flow meter readings?
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
Read Full Article