Pressure Drop Calculator
Calculate pressure drop in pipes using Darcy-Weisbach and Hazen-Williams equations
Input Parameters
Select method and enter pipe/fluid parameters
Method Selection Guide
- Darcy-Weisbach: Most accurate, works for all fluids and flow regimes
- Hazen-Williams: Simpler, for water at typical temperatures only
Results
Enter values and click Calculate to see results
Typical Pipe Roughness Values
| Pipe Material | Roughness (ft) | Roughness (mm) |
|---|---|---|
| PVC / Plastic | 0.000005 | 0.0015 |
| Stainless Steel | 0.0001 | 0.03 |
| Commercial Steel | 0.00015 | 0.046 |
| Cast Iron | 0.0005 | 0.15 |
| Galvanized Iron | 0.00085 | 0.26 |
| Concrete | 0.001 | 0.3 |
Formula Reference
Darcy-Weisbach Equation
h_f = f * (L/D) * (V^2 / 2g)
Where:
h_f = Head loss (ft)
f = Darcy friction factor (dimensionless)
L = Pipe length (ft)
D = Pipe diameter (ft)
V = Flow velocity (ft/s)
g = Gravitational acceleration (32.174 ft/s2)
Pressure Drop: dP = rho * g * h_f
Friction Factor (Colebrook-White Equation)
1/sqrt(f) = -2 * log10( (epsilon/D)/3.7 + 2.51/(Re*sqrt(f)) )
Solved iteratively or approximated using Swamee-Jain:
f = 0.25 / [ log10( epsilon/(3.7*D) + 5.74/Re^0.9 ) ]^2
Hazen-Williams Equation (US Units)
h_f = 10.67 * L * Q^1.852 / (C^1.852 * D^4.87)
Where:
h_f = Head loss (ft)
L = Pipe length (ft)
Q = Flow rate (ft3/s)
C = Hazen-Williams coefficient
D = Pipe diameter (ft)
Reynolds Number
Re = V * D / nu
Where:
Re = Reynolds number (dimensionless)
V = Flow velocity (ft/s)
D = Pipe diameter (ft)
nu = Kinematic viscosity (ft2/s)
Flow Regime:
Re < 2300: Laminar
2300 < Re < 4000: Transitional
Re > 4000: Turbulent