Coupling steel and copper pipes

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.
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Do you have access to the backside of the wall (the untiled side)? I think you want to be looking for a di-electric union so that the copper and steel do not react with one another.

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On Thu, 19 Feb 2004 10:39:13 -0800, "Doug McGinnis"

The only access I have is a small area in the back side of the wall, which is also tiled.
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Hate to say it, but I don't think compression fittings are going to be your salvation.
Compression fittings make a metal-to-metal seal on the outside of the pipe. In order for this to work, the outside of the pipe must be very smooth and round, with no surface irregularities, not to mention things like galvanizing or paint or corrosion. Most steel pipe doesn't meet this requirement - I think even if you could find a fitting the correct size it would probably leak like crazy.
Eric Law

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Brian Henderson wrote:

Nothing is impossible, Brian. Yes, there are compression fittings which will seal onto the outside of cut off iron pipes, and there are also space age adhesives which can help make things like that a reality. Hopefully the pipes themselves, if they're also from the twenties, aren't in such bad shape that they won't survive the operation. Your plumber is probably taking the prudent approach, based on his experience with old iron pipes.
Start looking around for what you need. Stuff like these:
http://doityourself.com/store/compressioncouplings.htm
It is not impossible for a dedicated and skilled craftsman to remove and ultimately replace antique tiles without damaging them, but you probably wouldn't want to have to pay the price to have someone do that for you.
Good luck,
Jeff
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Where I come from they're called dresser couplings. They come in galvanized, copper, brass and special ones for steam lines. Go to a local plumbing supply house (not Home Depot or a hardware store) and tell the counter guy what you're trying to do. If it's anything like the ones around where I live, the counter guys know at least as much, if not more, than the plumbers.

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Chances are your plumber's right, especially since not everything is measured only in dollars and cents. BTW, ever see one of those handyman guys who insist on spending 3-4 days mudding and sanding the existing walls of a bathroom straight instead of just spending one day tearing down the old drywall and putting up new drywall walls straight? I have. Thought it was a peculiar waste of time first time I heard about it, and nothing's really given me cause since then to think otherwise.
I get the distinct impression that you value the tiles, not the wall itself. There's undoubtedly someone in your metro area who can remove the tiles without marring them so you can rip down the wall, fix the pipes right like they ought to be fixed, and then put the tiles back up.
Might cost you a bit for that kind of tile-related skill to save those tiles, but once you figure in all the time and aggravation (and maybe even have to repair some related mayhem later on) all that jury-rigging to the existing stuff, might not seem like such a terrible cost.
BTW, just curious -- what makes 80-year-old bath tile that special?
AJS
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wrote:

The fact that every wall, including the floor, is covered in the tile up to about shoulder height and it isn't made anymore?
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wrote:

Because it's not common, it's not the same old homogenous shit as what's in houses built after WWII, and it's a testament to the durability of those older houses that were built so well in the 1920s and 1930s (of which I have owned three, all of which I loved, and two of which had original leaded and stained glass windows, which I certainly considered very special). Some of us like distinctive, high-quality surroundings.
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