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What is the recommended way to join hard copper to soft copper pipe

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by TimfromPittsburgh, Sep 8, 2012.

  1. TimfromPittsburgh

    TimfromPittsburgh Member

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    Western PA
    I am working on my water storage system and will need to join hard copper piping to my homemade heat exchanger coils that I wound from coils of soft copper tubing. Both are 3/4" diameter. I read somewhere in the past that soldering hard copper to soft copper is not recomended. Is that true? If so, what is the recomended method for joining hard and soft copper?

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  2. BoilerMan

    BoilerMan Minister of Fire

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    I have always soldered them together with a regular coupling. I have used soft copper in my domestic plumbing and all connections are soldered together with no ploblems. I have seen soldered connections between hard and soft in old buildings that have been that way for 50+ years and no issues. The only difference between hard (drawn) and soft (annealed) copper is the temperature that they make the pipe at. Annealing copper is bringing it to a certain temperature then letting it cool slowly. The copper is the same, therefore joining them is not an issue.

    TS
  3. mousebndr

    mousebndr Member

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    Silver solder will hold it no trouble.
  4. BoilerMan

    BoilerMan Minister of Fire

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    50/50 tin lead, or the lead free that is commonly sold at hardware stores. If you can/have the old lead solder, it works MUCH easier that the lead free stuff. Just use it on heating aplications, not domestic water.

    TS
  5. Bob Rohr

    Bob Rohr Minister of Fire

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    The one issue with soft copper is it is usually sold in rolls. When it is coiled it tends to oval or egg shape. Sometimes this makes it hard to get a fitting over and leaves a gap in the connection. Use a solder like Harris brand Bridgit "for ill-fitting or non concentric pipes" Bridgit has the ability to fill in large gaps, even better than 50/50%.

    Another option is a flare fitting which rounds the tube and provides a flared end to seal in the fittings. Flare fittings are the most common connection for underground soft copper joints. Some codes allow a silver solder or sil-phos solder, this requires a much hotter flame to melt, similar to a braze joint.

    Sometimes you can use a flaring tool to round up the tube, just don't drive it in to far or it will start to flare the end. Or a flaring bar that holds the tube can also be used to round up the tube it it is oval shaped.

    hr
  6. ozzie88

    ozzie88 Member

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    Another thing to consider is lead soilder has a burst point of only 150lbs. , the silver 95/90 burst is 600lbs. The joint will be alot stronger.
  7. ROVERT

    ROVERT Member

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    An adjustable wrench can easily be used to "round" copper pipe. Just adjust it until it has a snug fit around the hard copper. Then put the wrench on the out-of-round soft copper and rotate it around the pipe. It doesn't work quite as well as a rerounder, but it gets the job done.

    Not soldering hard copper to soft copper is a complete myth.
  8. ROVERT

    ROVERT Member

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    The local municipalities here no longer allow flare fittings for underground water services. Mueller compression fittings are now the norm. [​IMG]

    My flaring tool doesn't see too much use. It mostly only comes out for oil lines. It sees occasional use for gas lines, but they are mostly done with CSST now.
  9. BoilerMan

    BoilerMan Minister of Fire

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    Do you think 150psi is too low???? PEX has a lower pressure rating than 150 psi.

    TS
  10. ozzie88

    ozzie88 Member

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    No, 150lb, be ok for boiler I just happen to find this out when I was looking it up for some copper I used on a hyd. log splitter.[return side]

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