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  1. #1

    Question about a difficult to solder type of copper

    This is sort of a plumbing question, but I dont belong to a plumbing forum so I thought I would ask it here since I have been on this forum in the past and us refrigeration guys are very good solderers of various types of metals, more so than the average plumber I feel. I am almost embarassed to ask this question, however twice I have run into a problem soldering this old type of copper tubing. I call it old because both houses I have ever tried to solder this tubing in were built in the fifties. I have been working in refrigeration since 1990 and just recently started working for myself. And I now do all types of home repair and maintenance as well as refrigeration. But recently I had a job where a lady wanted some new cabinets installed and all the plumbing in them had to be replaced to install a new configuration of faucet and dishwasher, well im thinking excellent install some new copper (she specified copper), well when it came to soldering a coupling on the 1/2 inch pipe that was the "old stuff" the solder, just would not stick, flow or anything, whether I used my mapp gas or oxy-acetylene with regular plumbing solder. So I did what I did when I ran into this problem once in the past, I used my 45% silver solder and wahlah, it sticks. Anyone ever run into this, this tubing im talking about is black in color due to age, but when you rough it, its definitely copper. The only other time I've ran into to this is in a house my folks owned. I can only explain it as a weird make up of elements or the alloy in the tubing or something, it makes me feel like an idiot though as I can solder really well. All my new fittings after the old connection are a piece of cake, its like I know how to solder again. I knew as soon as I saw this tubing it was gonna be an issue because I saw it once before.

  2. #2
    Join Date
    Jul 2011
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    Here's what I would do. I would clean the tubing the best I could, flux it, heat it as if I am soldering, cool it with cold water on a cloth or heavy paper towel. This will help get it very clean. Then go at it a 2nd time for real. Sounds like your older copper may have some ferrous metal in it? I am assuming you are using 95/5?

  3. #3
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    Dont use water based flux!!!! I use the Johnsons flux, it looks like petroleum jelly... Not sure what flux your using but I soldered some inch and a half with the water based and well I thought i sucked at soldering too.... good luck!

  4. #4
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    tin the old pipe first this way you'll know for sue if the solder will flow.
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  5. #5
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    If the copper has annealed it will not take solder.
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  6. #6
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    if all else fails use sharkbites.
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  7. #7
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    Tinman hit the nail on the head. Sharkbite fittings. No soldering needed. They are a bit more expensive but they save a headache in situations like yours.

    http://www.sharkbite.com/usa/

    You can find them @ Home Depot, Lowes and any plumbing supply house.

  8. #8
    Join Date
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    Quote Originally Posted by Brent Ridley View Post
    Tinman hit the nail on the head. Sharkbite fittings. No soldering needed. They are a bit more expensive but they save a headache in situations like yours.

    http://www.sharkbite.com/usa/

    You can find them @ Home Depot, Lowes and any plumbing supply house.
    I like the sharkbite idea.

    I didn't know that annealed copper won't take solder. This is why I love this site. That said, I've never run into annealed copper, apparently.
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  9. #9
    Join Date
    Feb 2004
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    British Columbia, Canada
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    On old dirty ACR copper I automatically apply silver solder paste even when just using SilFos. You did well to use silver solder assuming you used the ss paste but you can also clean copper very well with TSP (trisodium phosphate) mixed with water. I saw plumbers do this on brand new fittings when they were installing medical gas piping in a hospital. Oxygen systems need a totally oil/grease free environment to prevent explosions and the TSP solution ensured that. They rinsed the fittings off afterwards and then let them airdry before brazing them with SilFos.

  10. #10
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    Quote Originally Posted by timebuilder View Post
    I didn't know that annealed copper won't take solder.
    I don't believe that is true. soft copper like linesets are annealed and they solder just fine. If the copper is overheated to the point of oxidizing then it will not solder, but the oxides can be cleaned off.


    Here in the Chicago area, we have a lot of houses that were build in the 50's that have hot water baseboard system that are piped in something that is not the copper pipe we are familiar with today. I suspect it is the same stuff that the OP has run into. I have never seen it used for fresh water, only heating systems.

    It seems to be some kind of tin plated steel, but at the same time looks like there is copper in it. All the original joints look like $#!& too, so it must have been just as hard to solder in the 50's as it is now.

    Sharkbites are a lifesaver when you run into this garbage. However I have had luck using oil based paste flux, and a high quality solder like staybrite or canfields

  11. #11
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    I have a house from the 50s, I had a hard time soldiering some old stuff, some of the old stuff won't come apart either when you try to unsweat them. I had a few joints I heated the hell out and wouldn't come apart.

  12. #12
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    Quote Originally Posted by craig1 View Post
    I don't believe that is true. soft copper like linesets are annealed and they solder just fine. If the copper is overheated to the point of oxidizing then it will not solder, but the oxides can be cleaned off.

    Let me rephrase it to "field annealing" lol. If my terminology is incorrect then please correct me. Annealing is the process of heating a metal until it's properties change. Field annealing would have occured when trying to solder with maybe water in the copper. The solder won't take and the copper becomes a greenish purpleish color. Also hard and brittle. Even after cleaning the copper and adding flux, the solder won't take. I practice my annealing skills normaly repairing condensate drains in freezers when there is residual ice in the line. I've heard an old plumbers trick is to stick bread in the pipe to absorb the water while the joint is being soldered, then just flush it out with a little pressure. Never tried that.
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  13. #13
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    Quote Originally Posted by Joehvac25 View Post
    I have a house from the 50s, I had a hard time soldiering some old stuff, some of the old stuff won't come apart either when you try to unsweat them. I had a few joints I heated the hell out and wouldn't come apart.

    I have also had this happen with freezer/cooler drains
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