mark used his keyboard to write :
So once pressure has been restored with gas only in the mains then every
house service has to be purged to get rid of any air nitrogen.

It is more complex than a water or electric main failing.

I do appreciate a good explanation and that was a good one.

Thanks Mark ^^

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk