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Gas pipe sizing calculator
Size natural gas pipework at 21 mbar with a 1 mbar permissible pressure drop from meter to appliance. Values reference the discharge tables in IGEM/UP/1B Edition 4 Appendix 4 and IGEM/UP/2 Edition 3 for copper (BS EN 1057) and medium steel (BS 1387).
1. Pipework
Rule of thumb: add ~0.5 m per elbow/tee and ~0.3 m per valve. Total effective length used: 8.0 m.
2. Appliance load
Recommendation
Total load
30.0 kW
≈ 2.79 m³/h
Effective length
8.0 m
straight + fittings
Smallest copper size that carries the load
22 mm
Capacity 5.00 m³/h at 8.0 m — 56% utilised.
| Size | Capacity (m³/h) | Verdict |
|---|---|---|
| 15 mm | 1.63 | Undersized |
| 22 mm | 5.00 | OK (56%) |
| 28 mm | 10.27 | OK (27%) |
| 35 mm | 19.67 | OK (14%) |
| 42 mm | 32.67 | OK (9%) |
For LPG, high-pressure risers or runs longer than 30 m, use the full IGEM/UP/2 tables and interpolate for the actual working pressure and permissible drop. Always cross-check the final design against the standard and site conditions.