Gas
Tightness testing of a gas installation
Test pressure, sealing and reporting on a safety-critical installation
Gas installations are among the most safety-critical parts of the plumbing trade, and they may only be carried out by authorised firms with the right certificates. A tightness test must prove there is no detectable leak before the system is put into service. The guide covers authorisation, test pressure, sealing and reporting.
Confirm authorisation and certificate
Gas work may only be carried out by an authorised plumbing firm with VFUL (full plumbing authorisation incl. gas) and the right certificates: A certificate for gas appliances up to 135 kW, B certificate for appliances/process plants over 135 kW (which also requires GFSA company approval). There is no «DIY» exemption for gas.
A/B boundary135 kWWork according to the applicable executive order
The applicable rule is BEK nr. 1702 of 17/12/2025 on the safety of gas systems and gas installations, in force from 1 January 2026 (replacing BEK nr. 253/2018). The authority is Erhvervsstyrelsen (merged from Sikkerhedsstyrelsen in Jan. 2026). The specific execution requirements are found in the executive order and the associated gas regulations/DGC instructions.
Check pipes, material and pressure
Check that the pipe dimensions and material are approved for the gas pressure and the gas type in question. Isolate the installation correctly before the test, and use calibrated measuring equipment intended for the purpose.
Apply the test pressure
For installations with an installation pressure of 100 mbar or less, the installation is tightness-tested up to the appliance's isolating valve with atmospheric air at a test pressure of 150 mbar. For higher pressures, the test pressure must be at least 1.5 × the installation pressure.
Test pressure (≤100 mbar installation)150 mbarHigh-pressure system≥ 1.5 × installation pressureRead off — there must be no pressure drop
Read the test pressure at the start and end of the test. No pressure drop may be recorded during the test period — a gas installation must be completely tight. Bear in mind that temperature changes can also shift the pressure.
Leak-test joints with soap or a sniffer
Pipes and fittings after the gas isolation valve and all joints are tested with soapy water or with a sniffer intended for the purpose and for the gas type in question. Before commissioning, the joints are soap-tested/sniffer-tested at normal installation pressure with gas.
Report deviations and document them
Any deviation from the DS standard on a gas installation must be reported electronically to the authority (Erhvervsstyrelsen). Collect the QA documentation and hand over the certificate to the client and/or the utility company.
Zero detectable pressure drop — gas does not tolerate «almost tight».
Source
Based on the Gas Regulations section B-4 and sik.dk «Klasse 7 — udførelse og idriftsættelse» (test pressure 150 mbar / 1.5×, soap/sniffer) and the worktree article «Gas installations in 2026» and the template «Checklist: gas installation» (BEK nr. 1702/2025, VFUL/A/B certificate, authority). Verify against BEK 1702/2025.