Derrick

All extremely interesting chemistry but straying slightly from the original question which was, what may be causing the blockage, if indeed, that is what it is. Many thanks for your knowledgeable answer, I am learning a tremendous amount from all your inputs.

I had already assumed that but thanks for your input, PeterF, much appreciated.

Right, thank you, got it now.

If water is an element of the gas and is released on combustion how or even why can it separate in the pipes when the system has not been used for so long and with everything turned off ? This problem has never occured before and the only thing that has been altered is the gas locker arrangement. Still two bottles on to the regulator but the pipework in the gas locker was done by the boatyard, but that was before the previous test. I still favour the water theory but how is what puzzles me.

No, I didn't, obvious really when you think about it. Thank you ?

I would love it to be as simple as that, it is possible that the 'U' bend under the regulator has an accumulation of water in it and I will check that, thank you. I was puzzled as to how water could enter the system but as you say if it is in the gas then that could well be the problem.

I can't see how to reply to individual answers but generally to all so far thank you. I cannot see any filters on the appliances, they are quite old Rose hob and separate cooker/grill. Good possibility of a blockage but no kinks in the pipe work. suspect something crawled in a died but can't imagine how. A slug of liquid ? Is that for me or in the pipe work ???? ? Good suggestion will check on that one, thanks. Disconnect the appliance and check.........I have to do that yet, just looking for other answers before getting 'up and under' to disconnect. Checked gas taps are 'on' thanks. Thanks to everyone so far.

I have recently had a boat safety survey and on checking the gas installation there was found to be a fault. The gas pressure at the first test point read correctly at or about 37 but on trying to light a ring on the adjacent stove the pressure dropped to 4. There was apparently no gas getting to the next appliance but the boiler which is the last in the line was reading 37. The examiner had never come across this before and neither have I. The system has been tested many times in the past and always passed with no problems. A new gas bottle has been fitted and there is no improvement. The system hasn't been used since the last test four years ago and I am wondering if anyone has any ideas on what the problem might be ???????????