Tightness testing is a core CCN1 skill because it is about proving a gas installation is not leaking before it is left in use. This page is a revision map, not a substitute for IGEM/UP/1B, assessment-centre training or supervised gas competence.
A tightness test proves whether installation pipework holds pressure, but the exact limits and method come from the current standard and assessment route.
Gas tightness test decision sequence
Use this as a revision prompt for the order of thinking. Live testing still follows the current standard, centre method and competent supervision.
- Identify gas type, installation scope, meter/control position and the procedure being assessed.
- Connect and zero a suitable pressure-measuring instrument at the correct test point.
- Prove no let-by before judging the installation pipework.
- Bring the installation to the required test pressure and allow stabilisation where the procedure requires it.
- Run the timed test and compare pressure movement with the permitted result for that installation.
- If the result is not acceptable, make safe, trace or repair within competence, then retest before returning gas to use.
- Do not replace a tightness test with a smell check.
- Do not skip let-by.
- Allow for temperature and stabilisation effects.
- Record the result and the action taken.
This card deliberately avoids live test pressures, timings and limits. Use the current standard, training route and manufacturer instructions for real work.
What the test is proving
The tightness test checks whether the installation pipework and connected fittings hold pressure. It is not a general smell check, and it is not replaced by leak-detection fluid on one joint. In assessment terms, it is a measured proof step before gas is left available to appliances.
The three ideas to remember
- Let-by: checking whether the emergency control or meter control is passing when closed.
- Stabilisation: allowing pressure and temperature effects to settle before judging the timed test.
- Timed test: monitoring the pressure for the required period and comparing the result with the allowed outcome.
Revision sequence
- Identify the gas type and installation scope.
- Connect the instrument safely and zero it if required.
- Prove no let-by before opening gas to the installation.
- Bring the installation to test pressure and stabilise.
- Carry out the timed test and record the result.
- Act on any unacceptable drop before relighting or returning appliances to use.
LPG and commercial context
Do not assume every gas installation uses the same figures. LPG, medium pressure, installation volume, meter capacity and commercial scope can change the standard or procedure used. That is why this page teaches the decision map, not a table of values to copy blindly.
Common exam mistakes
- Calling a smell check a tightness test.
- Skipping let-by before judging the installation.
- Ignoring temperature or stabilisation effects.
- Using leak-detection fluid as the only proof of soundness.
- Relighting before the installation has been proved sound and purged where required.
Quick answers
What are the stages of a gas tightness test?
In revision terms: let-by check, stabilisation, timed tightness test, result comparison, then repair/retest if the result is not acceptable.
Is a tightness test a legal requirement?
Gas work must be left safe and compliant. Tightness testing is a core method for proving an installation is sound before it is returned to use.
Can I use this page as the live test procedure?
No. Use the current standard, manufacturer instructions, centre training and competent supervision for live gas work.
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