How the installation volume is worked out
IV = pipework + 10% fittings + meter
Purge volume = 1.5 × IV
Pipework volume is each run's length multiplied by the internal volume per metre for its size. IGEM/UP/1B covers installations up to 0.035 m³ (35 L). For anything larger, use IGEM/UP/1.
Running the test
- Isolate the section and connect the gauge at the test point.
- Raise the pressure to the test pressure: 21 mbar for natural gas and LPG/air, 37 mbar for LPG.
- Allow 1 minute to stabilise, then watch the gauge for 2 minutes.
- Compare the drop with the allowance for the installation volume.
- If an existing installation passes with appliances connected, isolate the appliances and retest the pipework only. Any perceptible movement there is a fail.
Pipe volume per metre
| Size | L / m | m³ / m |
|---|
† Derived from nominal bore rather than the published table. Verify before relying on them.
Permissible pressure drop, existing installations
| Gas | Installation volume | Max drop |
|---|
New pipework, new installations and new appliances: no perceptible movement (NPM, 0.2 mbar or less). Meter volumes: U6/G4 8 L, E6 smart 2.4 L, U16 25 L.
This calculator helps with the arithmetic. Always work to the current edition of the standard and your own professional judgement.