"Set Square" wrote in message
...


SNIP


Have you examined the boiler yourself to verify the plumber's diagnosis?
Is
there any chance that there's just a leaking joint rather than a corroded
heat exchanger? The heat exchanger is probably in several bits which bolt
together - with gaskets to seal the joints. Unless there were a serious
manufacturing defect, it seems more likely to me that a gasket has failed
than that the metal has corroded through.

No its a one piece casting job with pipes straight into the ports, metal to
metal