Thank goodness the OP is apparently gas registered and has posted the question in the engineers forum where I will be pleased to help however simple the question.
There is a very good reason why the forum does not permit DIY gas advice! Whilst many people who ask questions are very capable and have responsible jobs in allied fields like the nuclear fission scientist, then there are also those who just read these forums and try to do it themselves when all their technical experience amounts to is changing a chain on a bicycle. For them it can be very dangerous.
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