Actually mprotsa your previous post I think asked a key question: "You have to ask yourself what has caused it to leak?" and a question that separates someone inexperienced in this area like myself with someone more experienced.
After some consideration of the advise I received from this forum, I decided to invite SafeGasInstall (Forum Trusted Advisor and recent work colleague on large site job albeit only for some days) to come have a look at this job before I did anything.
SafeGasInstall's initial assessment from the information given, would seem to have concurred with my work plan ie check and if necessary replace the expansion vessel and 3 Bar PRV on this now closed heating system - converted sometime ago.
However on visiting the site, he quickly identified a couple of other issues that may have caused the problem. In particular the expansion vessel was incorrectly positioned on the hot water side of the heating system, so that if heating only was requested then the heating had no access to the expansion vessel. He also pointed another issue which was perhaps evidence of the consequences of this design fault; there was leak on one of the connections into the nearby pump. Aswell as another possible cause: that the expansion vessel itself was incorrectly fitted being freestanding on the floor with its flexi constricted, to the point of almost being kinked.
Anyway he also made a number of recommendations increasing in price from just properly positioning and fitting the expansion vessel and repairing the connection into the pump, to, given the conventional boiler was somewhat dated, replacing it with a modern condensing boiler.
To conclude, yes the problem may have been temporarily sorted by replacing the expansion vessel or PRV. However as mprotsa suggests their failure may not be the cause of the problem. Indeed the apparent little problem with a leaking discharge pipe, was to flag more significant system problems. That this therefore means that only the 'very experienced' tackle heating issues is not something I think people were suggesting - how is anyone to learn?. Our objective I would have said, is to find an 'right' level of risk/benefit for the installer and client with the specific issue here being: whats enough experience? Answer: I dont know!
However having someone of 'system design & appreciable fault diagnosis level' experience, attend the issue at least on a supervisory basis, would be advisable, even for those with even minor doubts as to their competence. And imperative for those with little experience and often working solitarily, such as myself. Not so much because they may not be able to sort the problem - they often may. But because of the implicit assumption such people are likely to make, with especially heating systems. In particular that have been designed and installed correctly in the first place. And that therefore, its just a case of testing if parts have failed and if necessry replacing. This is less so the case with manufactured systems such as cars.
Many thanks to all, but especially Bob the plumber, Mike Jackson, crOft, mprotsa and of course SafeGasInstall.
michcosg
Afterthought
Another possibility, is that if you are visiting a customer for the first time to maybe, then get someone more experienced to review the system to insure that it at least has been designed and installed satisfactorily.
