JohnD,
they could see where the leak was coming from and then dug up the floor. They then saw the pipe was heavily corroded, and replaced the leaking section with a new length of pipe.
I fully appreciate that it is not reasonable for a business to be held responsible for installations they did not perform (not if they are to remain in business). I have been quite sympathetic towards the company concerned, and I will be honest in saying that they have made a lot of effort to repair the pipework, even though they did not install it.
But I am also a fully qualified professional engineer (in a different discipline) , and understand that the word 'professional ' has many connotations associated with it. These include adhering to strict policies and procedures, assessing risk and making customers aware of the risks and alternative solutions.
So, in this particular case, I would hope I would be treated in a similar fashion, in that:
a) I was made aware of the risks in installing a high pressure system in existing pipes buried in concrete,
b) advised of alternative, lower-risk options, and
c) adequate tests were performed to ensure that the system as a whole would function (that includes the existing pipes, which the new boiler must operate into).
The last point appears to me to be an obligatory responsibility of the installing company, since a new boiler that will not work (because the existing pipes can not handle the water pressure) is of no use to anyone.
This opinion also seems to be echoed by the Institute of Heating and Plumbing Engineers.
As a point of information, I did not go with the cheapest quote that I received, instead paying more to use a reputable company, who I believed would adhere to professional standards.