I posted about this a number of months ago, but I think I may have come up with a solution and was wondering a couple things.
First off, the story is this: I have a 1920s-era house with all original fixtures. The shower in one of the bathrooms has been leaking badly and I want to replace the valve assembly, which I've already purchased. The problem is that the steel pipes that were used are completely corroded and cannot be loosened. Yes, I know the best solution is to replace it all with copper, but because the only access to the pipes is through a wall of 1920s antique tile which is *NOT* replacable, I am not willing, under any circumstances, to rip out the wall to replace the showerhead line. I had a plumber friend come out and look at it and he basically said the wall goes or it doesn't get fixed. I replaced the valves and seats on the current assembly and it worked for a couple weeks, but it seems clear that there is a crack within the assembly that cannot be permanently repaired this way.
In the newest issue of Fine Homebuilding though, there was a way to simply cut all the existing pipes and solder in couplers between the old pipes and the new assembly. My question though is what is the best way to couple the new copper assembly to the old steel pipes? I've seen compression fittings for larger pipes, do they exist for smaller ones as well? Any idea how well they work? Once I finish the repair, I'm going to patch up the small hole in the wall with the few remaining 1920s era tiles I have and don't want to have to open up the wall again.