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Plumbing Pipe Size Calculator
Determine minimum pipe diameter for a given flow rate and pipe length using the Hazen-Williams equation
Plumbing
📋Hazen-Williams Equation (Q = 0.2785 × C × D^2.63 × S^0.54) — NBC India Part 9, Section 2
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Estimation tool only. Results are indicative — not a substitute for professional engineering design or site-specific survey. Always verify with a qualified civil, structural, or MEP engineer before ordering materials or commencing construction.
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Results are estimates only. Verify with a qualified engineer before use.
Formula
Hazen-Williams: Q = 0.2785 × C × D^2.63 × S^0.54 Rearranged for D: D = (Q / (0.2785 × C × S^0.54))^(1/2.63) Where: Q = flow rate (m³/s) C = Hazen-Williams roughness coefficient D = pipe internal diameter (m) S = head loss slope (ΔH / L), assume 0.005 m/m for typical domestic plumbing
QFlow rate (m³/s)
CH-W roughness coefficient (PVC=150, GI=100, Copper=130)
DPipe internal diameter (m)
SHydraulic slope (head loss per unit length) (m/m)
Reference Standard
Hazen-Williams Equation (Q = 0.2785 × C × D^2.63 × S^0.54) — NBC India Part 9, Section 2
Practical Tips
- •Recommended velocity for domestic supply pipes is 0.6–3.0 m/s; below 0.6 m/s causes sedimentation, above 3 m/s causes noise and erosion.
- •GI pipes corrode internally over time — modern construction prefers CPVC or uPVC as per NBC India Part 9.
- •For fire-fighting lines, NBC India mandates a minimum residual pressure of 0.7 bar at the highest outlet.