OT- Need advice on a plumbing (ugh) job please

[Gary Paine]

My daughter bought a vacant condo and turned the water on for the first time in over a year today. A major water leak was quickly discovered and she shut it off and called me. I'll help if I can, but plumbing is certainly not my thing. I'm hoping someone with experience can help me out.
The problem is a 1/2 inch copper line going into the shower valve. It was completely disconnected from the valve assembly. Examination and repair has to be done through a 6 inch diameter hole in the shower stall. It appears the valve was never hot enough for solder to stick, because although the copper pipe was tinned, there was no solder coating on the inside of the valve. I was able to use emery paper and clean off the end of the pipe, sanded the inside of the mating surface as best as I could get at it, and fluxed and reassembled the joint. It is ready to solder, but....
As I said, I am working through a 6 inch hole. I've removed the screws that hold the valve to the 2 x 4 brace and that lets me move it a bit. My plan is to cut and bend up some sheet metal to slip behind the pipes and try to protect the flammable stuff, use wet cloths and maybe vice grips and clamps if I can get them in there to prevent the heat from other joints, but I am really concerned that when I heat this up, other joints will lose their solder from the heat. The valve has 4 pipes, one at 12, 3, 6, and 9 o'clock all in a lump the size of a fist. The separated joint (9 o'clock) is only an inch from a t fitting on the feed pipe coming in and I can only see half of that fitting through the hole. I can and probably will make the hole an inch larger, but I think I'm probably dreaming that I can fix this joint without the others leaking.
I'm open to any and all ideas. I'm not sure I could fix this even if I busted through the wall from the other side. Any thoughts?
Oh, I'll certainly be taking a couple fire extinguishers with me.

[armedandsafe]

A lot depends on how close the other fittings are to the one you are soldering. I've had a lot of success in just clipping a vise-grip to the pipe a couple inches from where you are soldering.

Another trick I was shown by a professional plumber is to fill the back line with water, to within a couple of inches from the solder joint. If you do this make sure that the valve you are soldering is OPEN, so the resultant steam can escape.

Pops

[gnm109]

I've been there and done that and I'm not doing it again. Take my advice and call a plumber.

[Mcgyver]

get one of those $2 atomizers, fill it water and wet down the insides...since you have limited access this will allow you wet for some distance beyond what you can reach. Any piece metal directly behind the pipe so the flame isn't hitting a 2x4 or drywall is good, but I've done this most times just be wetting things....its really not a big deal.

you're not going to have the heat on for very long, just drape a wet rag over any close joint to prevent unsoldering them. You'd have to really work at to wreck a joint a foot away....drape a tie a wet rag around the pipe to protect anything less than say 10"

if you uncomfortable practice a bit outside the wall with some fittings and copper....you'll get the hang of it in short order and have more confidence going into the wall cavity, but if you're really anxious about it get a plumber

[Gary Paine]

get one of those $2 atomizers, fill it water and wet down the insides...

Great idea. I can certainly do that.

Do you think the wet rag trick will save the solder joints on the t that is only an inch away from the joint I have to solder?

And I agree on the plumber, but I since she spent all her money on the new place, I know who'll pick up the tab, so with little to lose, I might as well try it myself if I can do it safely.

[Mcgyver]

I re-read your post, with the idea of a cluster as you describe it. The wet rag trick is really effective in my experience, so weave and tie as best you can all around the cluster. If you've tied off a wet rag on the far side of a fitting, it should protect this side of the fitting as well.

Even if there was a very good chance the solder on one an inch away would melt, so what, you touch you flux core solder to it while you're in there. If it melts, you fixed the solder joint you unsoldered, if doesn't you didn't unsolder it

unsolder is a misnomer as well...ever heat a joint let it cool then try to get the pipes apart? there's surface tension etc at work that will keep the solder in the joint you think you've unsolder...it cools and is soldered again...but like i say i add a little for good measure in case miraculously the solder drained away.

To me the challenges are not burning down the building, making sure the pipes are not full of water (ie acting as a heat sink) and not getting in trouble with the condo corp for being a non licenced person blah blah blah...the cooper soldering part is child's play compared running a lathe

But again only go at it of you feel good about it

[Carld]

Be sure the home owners insurance is paid up before you attempt a repair. Have someone ready to call the fire department whether you do it or a plumber does it.

You need a torch with a hot fine flame.

[winchman]

I'd be talking to the lawyer who handled the sale about this. There's very little chance the previous owners didn't know about this, and they have an obligation to report it or fix it.

Ditto on calling a plumber.

[rancherbill]

You have thought it through with the heat shield, fire extinguisher etc.

My guess is, it did not work the first time was because there was not enough heat to get the solder to flow. There is a lot of copper in there and it sucks heat like crazy and it hard to get it hot enough to truly flow the solder.

Use as a minimum Mapp Gas or or the plumbers Acetylene mix(?) . You need a ton of heat in this location.

It will go well.

[lakeside53]

I do this all the time. Heat shields correctly placed work well... and the stud will take a lot of charing... for shields, I use thin steel sheets and 1/4 inch Hardibacker. The woven shields are pretty much worthless with direct flame unless you can find the old asbestos version. Remember, heat will travel UP the stud bay. Use a lead-free solder with about 0.4% silver - much better flow than the non-silver types.

I assume you have taken the valve part - no o-rings or plastic parts inside?

The other connections will not let go with the heat - I doubt they will even get to melting temperature. Use Mapp gas and work fast. Rather than a fire extingusher, use a hose - quick squirt will take care of things and no obsuring clouds or chemical mess.

If you're not comfortable, take out a lot more sheetrock, or call a plumber.

You say it's all fluxed, but you are on this forum. You should not leave most fluxes for more than about 30 minutes.