Guys, Wonder if you might be able to offer me some advice. I'm a plumber (not CORGI registered). Yesterday I fitted a new radiator into an existing system. The heating is provided by a combi boiler. I drained the system before fitting the radiator. Once all the pipework was in place and the unit fitted I continued by filling the system. The filling loop was controlled by means of a washing machine tap, the handle was missing and could only be opened using a spanner or pair of pliers. I filled the system to 1.5 bar as is the norm and went to bleed the system. Unbeknown to me the washing machine tap was faulty and would not fully close. Resulting in the system offer pressurising. The first thing I knew of the problem was when the pressure relief valve opened to dump the excess water. This did not shut off though and the pressure dropped to 0 bar. When I noticed what was happening I attempted to close the washing machine tap again, however it would not fully close. I tried to turn the mains stop tap off only to find that this didn't fully turn off either. Upon looking at the boiler again I noticed water streaming down from within it. I suspected that the expansion vessel had blown. The customer has British Gas cover, when they came to look at it last night they said the expansion vessel had burst because of over pressurising the system too fast (in my opinion I hadn't at all). They have said that it would cost the same to replace the vessel as it would install a new boiler!, as the boiler and flue has to be removed to gain access to the vessel (sorry don't have the details of the make or model). The cost for the wok is £1500!!! My question is this, would you think I am liable for the cost? I believe the washing machine tap was at fault, I removed this and replaced it with a similar valve, leaving it with the customer (he has since said that it has been thrown out). I accept I was the last to touch it and that the damage happened as a result of me filling the system but I have done it hundreds of times in the past so I know what I'm doing. I'm being threatened with legal action if I don't rectify the problem. Your comments would be appreciated. Mark p.s. As I'm not CORGI registered can't sort out the problem myself, Any idea of the cost to replace a combi's expansion vessel in the Leeds area?