It's seemingly becoming increasingly likely you're right - and it certainly wasn't me who thought, let alone claimed, that there is such a regulation. However, as has been said (not the least, by me!) many times before, in a situation like this the absence of proof is not proof of absence.As no one has yet dug up such a regulation we must presume there is no such regulation.
Are there no lurking plumbers of gasmen/gaswomen who could referee for us?
Kind Regards, John
