some gas pipes aren't the same size as water pipes. which is why they may not work or be interchangeable

that and the fitting might not be properly sealable against the gas

i know we had a world of trouble tring to sort our gas pipes out when we moved in, in the end we got the gas man to start from scratch as my brother decided to put screws through the pipework on 2 separate occasions

twat was without gas until they could come out and sort the problem, they put a prohibition notice on