Tulloch PriestCo-founder, Gas Engineer Software · Co-founder of Gas Engineer Software

Why you now have to isolate appliances when you find a leak

6 May 2026 · 1 min

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When you find a leak, you now have to isolate connected appliances to figure out where it's coming from. If you can't isolate an appliance, you have to assume worst-case and use the largest installation volume, which limits pressure drop to just 1 millibar. That tight tolerance trips up a lot of testers.

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One of the biggest changes that people still seem to be not really able to get their head around is you now, if you find a leak, you now have to isolate the appliances as part of this new procedure to be able to test whether the leak is pipework or the appliance, something that before you didn't have to do, but now you do. So for whatever reason, there is no way you can isolate an appliance, then you have to go with worst case scenario, which is basically the largest installation volume that we're allowed to go to, which is only a 1 millibar drop. And that's going to catch people out.