Pipe Sizing Tool

Tradify — Pipe Sizing Calculator

Quick, practical sizing for residential water and gas lines. Indicative only—always check local code.

Inputs

Unit system

Pipe material (affects inner diameter list)

Flow rate

Typical residential outlet: 6–12 L/min (1.5–3.0 GPM). Tankless HWC intake can be higher.

Pipe run length

Include an allowance for fittings (e.g., +30%).

Pressure drop allowance

Water common: 100–300 kPa (15–45 psi) across branch runs.

Results

Recommended size

—

Nearest standard (by material)

—

Check velocity (water)

—

Assessed on

—

Notes & Assumptions

Water sizing uses a simple velocity-based method: target 1.0–2.0 m/s (≈3.3–6.6 ft/s) to limit noise/erosion.
Gas sizing uses a simplified capacity lookup (0.25–0.5 psi class) with diversity factor ~0.6. Treat results as indicative only.
Always verify against local code/tables (IPC/UPC, BS/EN, AS/NZS) and manufacturer requirements.
Include equivalent length for fittings when estimating run length.
These results are indicative only and not engineering advice.

Formulas

Water — velocity method: For flow Q (m³/s) and target velocity V (m/s), required inner diameter D (m) is D = sqrt(4Q / (πV)). We choose the smallest standard size with ID ≥ D. We display resulting velocity for the chosen nominal size.

Gas — simplified capacity lookup: Total diversified load Q_gas = 0.6 × (sum of connected loads). We compare against an approximate capacity table by nominal size and length; linear interpolation between breakpoints is used.

Conversion: 1 L/min = 0.0000166667 m³/s; 1 GPM = 0.000063090 m³/s.
1 in = 25.4 mm; 1 ft = 0.3048 m; 1 psi = 6.89476 kPa.
1 BTU/h = 0.00105506 MJ/h (≈ 0.001055 MJ/h).
These numbers are indicative only, consult a certified professional for final sizing.

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Pipe Sizing Tool

Pipe Sizing Tool

Inputs

Results

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