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Thread: Problem sweating second joint on a fitting

  1. #1

    Default Problem sweating second joint on a fitting

    It's been a while since I've sweated copper pipe, and I'm running into a new (for me, anyway) problem...

    I assembled the whole thing, cleaned and fluxed, and started sweating the joints. I noticed that the first joint on a fitting typically went very well, but the second one often didn't. The solder just wouldn't flow right.

    I think what was happening was that the flux in the second joint of the fitting was just getting oxidized out while I was sweating the first joint.

    How does one avoid that, especially on smaller joints such as couplers?

    And a second question...how likely is it that a joint that passes muster when first put under pressure will fail sometime later? Can I be fairly certain that a joint passing the initial pressure test will remain good?

  2. #2
    Plumber Cass's Avatar
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    Nov 2005
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    Default

    Practice...is the tubing open to the air some where so that your not trying to solder a closed system...?

    You are most likely getting the fitting to hot....try heating the whole fitting at the same time..

  3. #3
    Master plumber Jay Mpls's Avatar
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    Sep 2008
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    Minneapolis
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    Default

    It is always my luck after the house has drained down I have to outlast or outwit water from something.Kind of sounds as though you *may* hae been fighting water.
    Every now and again I have expansion from the water heater to contend with.
    On a short closed system you may have been fighting pressure from your own heat.
    Beyond that, it's all in the preperation!

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
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    Default solder

    Do not stop after each joint. Do one, usually the largest, then the next, and so on. For a vertical line do the lower joints first and then work upward.

  5. #5

    Default

    Thanks all for your help.

    It turns out the issue was flux. I originally bought a "kit" containing some solder, some flux, and a flux brush, and the flux was obviously not very good. I ran out, went to the store to get some more, and the guy there said "don't use that junk..try this!". And "this" worked wonders. Every joint I sweated after that worked perfectly (and I don't think my technique had miraculously improved, either!).

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