How to Calculate Pipe Sizing
What is Pipe Sizing?
Pipe sizing selects appropriate diameter to convey water at acceptable velocity and pressure drop. Too small causes excessive friction; too large wastes material.
Step-by-Step Guide
- 1Apply Hazen-Williams or Darcy-Weisbach equations
- 2Velocity typically 0.6-2.4 m/s for water systems
- 3Calculate diameter and pressure drop
Worked Examples
Input
Q = 0.05 m³/s water flow, C = 150 (PVC), L = 100 m
Result
D ≈ 50-63 mm for <1 m/100 m drop
Hazen-Williams estimate
Common Mistakes to Avoid
- ✕Using smooth pipe assumptions on old systems
- ✕Neglecting temperature effects on viscosity
Frequently Asked Questions
Why limit velocity?
Too high velocity causes excessive friction loss and noise; too low allows settling and corrosion.
How does pipe age affect sizing?
Roughness increases with age, increasing friction losses. Design for aged conditions.
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