Gas Pipe Sizing Calculator (beta)
Size a gas run and check it against the 1 mbar BS 6891 allows.
For planning purposes only.Beta — not yet reviewed by a qualified engineer.Detail
Copper implements BS 6891:2015, not Amendment 1:2019, and Tables A.1 and A.5 were checked row by row against the published standard. Steel and stainless are not in that standard at these sizes: they are computed from the flow equations, calibrated against Table A.1, on EN 10255:2004 Table 2 bores, and the permitted drop is the figure you enter rather than one taken from a standard. Tell us if something is wrong.
Pipe
No fittingsChange
Enter the rating and the run length.
Method and standard
Method
Adjusted length = measured run + fitting allowances (Table A.5); section drop = mbar/m (Table A.1) × adjusted length; the drops along each meter-to-appliance route must total ≤ 1 mbar
Reference
BS 6891:2015 — Table A.1 (natural gas pressure loss, copper tube), Table A.5 (fitting equivalent lengths), Annex A method. Supersedes the withdrawn BS 6891:2005+A2:2008. Natural gas in copper only: steel (Table A.2) and LPG (A.3/A.4) are published by the standard but not implemented, and stainless — rigid or corrugated (CSST) — has no BS 6891 table at all and is sized from the manufacturer's data.
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