Completion certificate before a failed tightness test
A registered gas contractor is completing a 28-storey residential tower. The developer's project manager wants the completion certificate for the gas installation issued before the final tightness test, because the occupation permit review is the next morning. The supervisor's test on a 6th-floor riser section shows a pressure drop of 0.7 kPa over 10 minutes, about three times the contractor's own acceptance criterion, and a soap test finds a weeping joint at a reducer. The project manager says the joint can be re-torqued and the certificate signed now, with the retest to follow after handover. The contractor's registered installer is on another site and cannot attend until the afternoon. The supervisor is also told that delaying the certificate will affect the contractor's grading under a framework agreement.
1. What are the supervisor's professional and legal duties when asked to issue the certificate?
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The supervisor's first duty is public safety, not the occupation permit. A completion certificate is a formal statement that the installation has been tested and complies with the Gas Safety Ordinance and the applicable regulations/code. A 0.7 kPa drop over 10 minutes, about three times the contractor's acceptance criterion, is a failed tightness test; the soap test confirms a leak at the reducer. Signing now would be a false or misleading certification and could expose the contractor, the registered installer and the supervisor to enforcement action and professional consequences. The supervisor should refuse, stop work on the affected section, isolate and depressurise it, and report the instruction to the contractor's responsible person in writing. Commercial pressure from a framework agreement or a project manager does not override the duty. The correct sequence is to repair the joint, investigate why it leaked, retest, and only then certify. The supervisor should keep a contemporaneous record of the request, the test readings and the refusal.
2. Assess the technical risk of signing now and describe the correct repair and retest sequence.
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A leak on a 28-storey riser can accumulate gas in the shaft or plant room; town gas is buoyant but not harmless, and an explosive atmosphere plus an ignition source is credible. Re-torquing a weeping joint without breaking, inspecting and remaking it may leave a damaged thread, seal or fitting; the leak may be behind the reducer or in the pipe thread. The correct sequence: isolate and purge the section; remove and inspect the joint; replace damaged fittings with approved components; remake to the manufacturer's method; carry out a strength test if the joint is part of a new installation; then a tightness test at the specified pressure and duration with temperature stabilisation and calibrated gauge; soap-test all joints; purge; and commission appliances. A retest after handover is not acceptable because occupants could be in the building and the riser could be live. The supervisor should also check whether the failed joint indicates a wider workmanship problem and sample other joints in the same run.
3. How should the supervisor communicate and document the refusal, and what if the pressure continues?
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Communicate in writing: a stop-work notice or non-conformance report to the project manager and the contractor's authorised signatory, stating the test pressure, duration, measured drop, acceptance criterion, the soap-test result and the location. Offer a recovery plan: immediate repair, retest, and an inspection by the registered installer or an independent competent person; if the developer needs partial occupation, consider certifying only unaffected, separately isolated sections if the code allows and the certificate is clearly scoped. Do not sign the whole-building certificate. Escalate internally if the project manager persists; keep emails, site diary, photographs and test sheets. If there is an immediate danger to occupants, notify the building owner and the gas authority as required. The framework agreement is irrelevant to the technical decision. A useful test of the right answer is: would the supervisor be willing to defend the certificate in court or at an inquiry after an incident? If not, do not sign.