Installation Volume Calculator (beta)
Add each run of pipe, pick your meter, and get the installation volume in cubic metres and litres. Under IGEM/UP/1B Edition 4 this is the number that sets your permitted pressure drop, and it sets your purge volume too. Both come out with it.
Beta — not yet reviewed by a qualified engineer.Detail
Works to IGEM/UP/1B Edition 4, mandatory from 1 October 2026. The Edition 4 figures are transcribed from a published secondary source rather than a licensed copy of the standard — check them against your own copy before you rely on them. Tell us if something is wrong.
The PDF is a calculation record, not a certificate — it carries no declaration and no signature. To issue the real record, carry these figures into the certificate.
Method and standard
Why the volume comes first
Under Edition 4 the volume is the whole ballgame. It sets how much pressure drop you are allowed, and it sets how much gas the purge takes. Get it wrong and every figure after it is wrong too.
The three parts
IVt = IVp + IVm + IVf — the pipework, the meter, and the fittings. Fittings are taken as 10% of the pipework rather than counted one by one.
The copper figures already carry that 10%, so a metre of 22 mm is 0.000352 m³ as it stands. A U6 or G4 meter adds 0.008 m³ on its own, which on a small job is most of the installation.
Why steel asks for a bore
The copper figures check out two ways: two independent published sources give the same four numbers, and working them back to a bore lands on BS EN 1057 tube. The steel figures do neither. They imply bores well above real BS EN 10255 tube, by an amount that varies size to size, and no second source publishes a steel table to check against. Rather than ship four numbers we cannot derive, steel goes through a bore you measure.
The 0.035 m³ line
Past 35 litres UP/1B stops. There is no permitted drop tabulated above it and the test belongs to IGEM/UP/1A or UP/1 instead. IGEM/UP/1 also wants a written purge plan at that volume.
Next
- Tightness test calculator — turns this volume into your permitted drop.
- CP16 non-domestic testing & purging record — records the estimated pipe volume.
- Domestic testing & purging record — records the allowable pressure drop.
Method
IVt = IVp + IVm + IVf — pipework plus meter plus fittings, fittings taken as 10% of pipework. Purge volume PV = 1.5 × IVt.
Reference
IGEM/UP/1B Edition 4, mandatory from 1 October 2026. IVt = IVp + IVm + IVf, with fittings taken as a tenth of the pipework. Copper uses the standard's tabulated cross-sectional areas — 0.00014/0.00032/0.00054/0.00084 m² for 15/22/28/35 mm — which two independent published sources give identically, and which work back to BS EN 1057 tube. Steel presets are deliberately not offered: the published steel figures imply bores well above BS EN 10255 by an inconsistent margin and no second source publishes a steel table, so steel goes through a measured bore. The 0.035 m³ written-purge-plan threshold is from IGEM/UP/1.
Related calculators
- Gas Rate Calculator — Convert meter readings to m³/hr and kW for natural gas or LPG.
- Flue-Gas Ratio Checker — Get the CO/CO₂ combustion ratio and its BS 7967 action band.
- Gas Pipe Sizing Calculator — Size a whole installation against BS 6891:2015, section by section.
- Tightness Test Calculator — Get the maximum permissible pressure drop from your installation volume.