Hazen-Williams Water Flow Formula: Head Loss Calculator
Calculate friction head loss in water pipes using the Hazen-Williams empirical equation. Determine head loss per 100 feet of pipe and total head loss for a given pipe length.
Hazen-Williams Head Loss Calculator
The Hazen-Williams equation calculates friction head loss in water pipes:
h₁₀₀ft = 0.2083 × (100 / c)^1.852 × q^1.852 / d^4.8655
Where:
- h₁₀₀ft = friction head loss (ft H₂O per 100 ft pipe)
- c = Hazen-Williams roughness constant
- q = volume flow rate (gal/min)
- d = inside pipe diameter (inches)
Flow Velocity
v = 0.408709 × q / d²
Where:
- v = flow velocity (ft/s)
Limitations
The Hazen-Williams equation is assumed to be relatively accurate for water flow when:
- Reynolds Number is above 10⁵ (turbulent flow)
- Water temperature is in the range 40–75°F (5–25°C)
- Kinematic viscosity is approximately 1.1 cSt
For hotter water or other fluids, the Darcy-Weisbach method is recommended.
Example
Given:
- Flow rate: 200 gal/min
- Pipe diameter: 3.048 inches
- Roughness constant (PEH pipe): 140
- Pipe length: 30 ft
Results:
- Head loss per 100 ft: 9 ft H₂O
- Total head loss (30 ft): 2.7 ft H₂O