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is this the right flux for silver soldering copperpipe?

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  1. #1
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    Default is this the right flux for silver soldering copperpipe?

    ive got a 200g container with a white and pink label that says

    CIGWELD COMWELD
    G.P. SILVER
    BRAZING FLUX

    Contains: Boric acid 415mg/g
    Potassium Bifluoride 315mg/g
    Potassium Hydroxide 90mg/g

    Will i be able to join copper pipe with this stuff and a 2% silver solder stick with a yellow tip?
    using MAPP Torch one of them benzomatic things TS4000.

  2. #2
    Retired Marine Engineer 1K Club Member Ashore's Avatar
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    No mate its not, you don't technically need flux with silver solder on copper pipe ,it will work and some like to use flux but others don't , the tricks are don't over heat get the job clean ( spotless) , have a good sliding fit ( silver solder doesn't like big gaps) and don't put the rod into the flame get the pipe hot enough ( but not too hot ) and touch the rod on the copper tube and the silver solder should melt and run , could show you but its hard to explain
    Ashore




    The trouble with life is there's no background music.

  3. #3
    China
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    Default

    You will only need the flux if you intend to connect brass fittings to the copper pipe

  4. #4
    Golden Member Gooner's Avatar
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    Wozza... don't bother with it if you are brazing copper with copper. I did a lot of copper-copper brazing a little while ago with a Bunnings MAPP torch. I can give you a few tips.

    If there is water in your pipes you will struggle. The water will act as a heat sink and it will be very difficult to get the copper hot enough. If you are brazing 3/4" pipes make sure there is no water within 1-2 meters of the spot that your brazing. It is hard enough already without water when using a MAPP torch. 3/4" pipe is the limit, and I did struggle in places even where there was no water in the pipes. 1/2" pipe is much easier. If there is no water in the pipes then it won't present too much of a problem.

    Careful how you apply the heat. There are a few threads on this forum on how to do it properly. Keep it even making sure not to overheat. The copper has to glow cherry red. At this point apply the silver solder to the join. Do not heat the solder purely with the flame. It is the heat of the join that has to draw the solder into the gap. If you heat it with the flame it will simply melt and "cover" the join but no seep into it.

    Don't bother using flux, but make sure the connections are shiny clean and relatively tight fit. Get some fine steel wool and polish up both mating connections before brazing. The copper should be shiny.

    You will know when you have done it properly as you will literally see the silver solder getting sucked into the join. If not, it hasn't worked properly.

    Keep in mind I am no expert so take my advice with a pinch of salt. Having said this, all my joins worked out well but it took me a few practice goes to get it right.

    I never did have much success brazing brass fittings with the MAPP torch though. Could never get the join hot enough.

    The flux you bought is the right stuff for silver soldering, but not necessary with copper/copper. Silver solder flux will contain Boric Acid or Borax.

    Hope this helps.

  5. #5
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    I thought you said you where getting a plumber wozza when you thought I was picking on you Go for it mate sounds like you got it sussed with the 2% silver and all!
    Plumbers were around long before Jesus was a carpenter

  6. #6
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    Quote Originally Posted by wonderplumb View Post
    I thought you said you where getting a plumber wozza when you thought I was picking on you Go for it mate sounds like you got it sussed with the 2% silver and all!
    i am, he is coming this wednesday, i want to try and do a bit myself on the outside to try and save some time and labour and get some experience. he can redo it if its not good enough. and im only connecting up an external tap from a rain water tank, im not touching the house plumbing, he is doing that.


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