Copper joint won't hold!!!

[DIYMike]

I'm sweating a Moen tub rough-in valve assembly. here is a link to the assembly: Moen part # 4999

The tube from the each valve to the "T" are heavier gage 1/2 copper. I have a short standard 1/2" copper piece between the "T" and the outflow tube.

When welding the T fitting, the solder doesn't seem to want to draw inside. On the "hot" side, it sucked in, and on the outflow side, it sucked in, but on the "cold" side, it just seems to melt at the edge of the "T"... and not get drawn in.

I had the whole thing assembled, then installed, and the "cold" side leaked (my first leak ). I tried to sweat it again, but it didn't hold. A small fracture was apparent between "T" and the solder bead on the outside. So I took it all apart, cleaned, reamed, and tried to resolder with a fresh "T". Same problem, and again, on the cold side.

What am I doing wrong? When has a fitting had too much heat? Why won't it draw in? I've welded hundreds of joints, and have never had this problem...let alone on the same joint twice.

Thanks!!!

 

[Terry]

​

Fittings and pipe need to be clean, and the pipe should be fluxed.
I don't know if you used flux, but without it, the solder won't adhere.
I've never tried welding copper fittings.
I use a torch and solder them with "no lead" solder.

A little emory cloth helps to clean the pipe.
heat should be applied evenly.

 

[Sponsor]

 

[DIYMike]

Thanks Terry.
Yes - I meant sweating... Propane torch, solder, flux, etc. I'm using the bristle brushes for inside and outside of the joints. Then fluxing, and assembling.

the first time - all joints were "new" and clean. When I disassembled the joint, the "Hot" side (the one that took) was covered in solder. I heated it up and tried to brush some of the solder off. No matter what I do, I cannot get it back to pure copper. But, this "hot" side, seems to have held fine when re-joined.

The "cold" side, the one that fell apart, when I took it apart, there was almost no solder on the pipe. it looked burnt. But a few twists and the the copper on the leaking side was back to shiney copper. So i fluxed it, and a new "T" and tried to reheat the joint.

Same problem, the "hot" side was fine, but the "cold" was not. The hot side had residual solder, the cold side was shiney copper.

Is the thick factory tubing causeing this? With normal joints.. I just heat them up and they suck in the solder... but this one is killing me.

 

[Terry]

You got me.
It sounds like you are getting it clean with your wire brush.
A third time?

 

[hj]

joint

You are describing a joint that is either getting so hot it is burning the flux, or you are getting some water at the joint, or possibly both. Either one will prevent the solder from flowing.

 

[DIYMike]

Any special tips to re-soldering? When I separated the pieces last time, one side was covered in solder, the other was bare. I was not able to scrape off the solder. The other side shined right up. So I added flux to both at reattempted the joint.

So - the one that originally worked (which still had solder on it) was resoldered without getting the pipe back to the shiney copper .

The other side - which originally failed, came out almost clean. It was easy to brush this down.

Is this correct for re-soldering? I replaced the fitting, but the pipes are factory attached to the valve and I cannot cut them to get a "clean" piece of copper. Is it OK to have leftover solder from a previously good joint?

 

[Mike Swearingen]

http://www.easy2.com/cm/easy/diy_ht_index.asp?page_id=35694426
"How To Sweat Copper Pipe"
Tips: Heat the fitting, not the pipe, and move the heat around, as well as the solder (around edges). Most common DIY mistakes: over-heating and trying to solder with water in the pipe.
Good Luck!
Mike

 

[DIYMike]

Thanks Mike.
That's a good site. Same info as all the DIY books, except for the flame length.

I read somewhere that if there is a leak, to disassemble, replace the fitting and clean the pipes, not to just try to reheat it. What's your take?

Also after disassebling... is it necessary to get back to bare shiney copper? I have a joint that is well coated with solder and I tried to heat it up and wire brush it off... but it stays silver. Tried to sand and brush it - nothing. So - can I just reflux and go?

 

[SteveW]

I'm pretty sure (but hopefully one of the pros will confirm this) that it's OK to resolder the pipe as is that's already covered with solder. It's "pre-tinned." Just my DIY experience.

 

[DIYMike]

Well, it seemed to have worked this time. I could definately tell that the capilary action was in play. Tub is all hooked up and no leaks. Gonna give a few days before I lock it in.

First, I did a test joint on the old valve assembly. It also took a long time, but when I was done, i took it apart and it appeared that the solder was well spread around the whole joint.

Then I took it all apart, cleaned everything well, fluxed, assembled, and heated. It takes a long time to heat a T with 2 "k" tubes and a brass outflow all attached. I wonder if they make a "k" guage "T" to absorb the heat better?

Oh well, time will tell...

Thanks all for your help!

 

[Gary Swart]

I think that's why most plumbers us Mapp gas instead of propane.

 

[DIYMike]

Does MAPP come in the same canisters and propane? is it reasonable for a DIY'er?

I'm a little confused. Does the higher temp heat it more evenly or faster? Why is it better?

I also thought that part of my problem was that I was heating the fitting TOO much and burning the flux. Won't MAPP just do that quicker?

 

[Terry]

If your're burning the fittings, then MAP won't help you.

I use MAP because I don't like to wait, however, I've been doing this for years.
There's nothing wrong with LP gas. It works fine.
For the homeowner I would think better.