One of a homeowners nightmare problems, would be owning an nice older home with hydronic heating and have the piping develop some leaks. Especially so if it sits on a slab foundation, or maybe is a 2 story Victirian with all the interor and exterior walls in excellent condition. Having to repipe the heating system traditionally involves breaking up concrete and tearing into walls to reach the upper floors.
There is a process, not for a doityourselfer, that can save all that destruction and the subsequent re finishing every thing.
It comes from They can apply an epoxy liner to pipes after cleaning then, all in a non invasive manner. Nu Flow. (//http://) Somewhat akin to getting a stent placed in an artery.
I just thought it was very interesting. Hope nobody ever needs it.