I don't know what your problem is, but I am not a liar. That is what I was told, whether it was true or not I cannot say. I also cannot comment on, whether they would have fixed it or not but the first time it was done under warranty & the second time I paid. Neither time was dirty water in the system mentioned. Given that you were not involved in either of these repairs I would suggest you think twice before calling anyone a liar. I would also draw you attention to this
http://idealboilers.com/installers/products/boiler-range which clearly states that the later models have stainless steel heat exchangers.