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Solder or braze small copper aircon pipes?

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  1. #1
    Join Date
    Sep 2010

    Default Solder or braze small copper aircon pipes?

    I posted in the heating/cooling section, but probably should have posted here in plumbing.
    Did not get an answer, so hope it is OK to repost where it is more likely to be seen.

    Quote Originally Posted by tundra View Post
    I pickup up a small used split system for a DIY install, but found the pipes from the indoor unit do not have the expected brass flare connector.

    The copper pipes have been cut and pinched closed. I guess the original installer must have brazed the pipes rather than using a flare joint?
    The question is how to recover.
    Being only 1/4" and 3/8" pipe, can I get away with soldering and a butane torch, rather than brazing?
    I have installed split systems before, using pre-flared hoses. Have not done plumbing soldering, no brazing tools, and have done only low-pressure flare joints.

    I have one of those 3m pre-flared pipe kits. Should I :
    1) cut the flare off pipe and solder using a copper connector to the inside unit?
    2) use "double flare unions" like this? https://www.gameco.com.au/product/do...ion-14-cw-nut/ (No new skills needed)
    3) get connectors with copper tail to solder on, restoring it to like a new inside unit. https://www.aliexpress.com/item/4000110755832.html

    A complication is that it will be installed on a double-brick wall, and with the pipes cut short I'll probably have to do the join before mounting the unit, then feed the 3 metre pipes through wall.

    thanks for reading, hope it makes sense.

  2. #2
    Seasoned DIY droog's Avatar
    Join Date
    Sep 2005


    There is soldering and then there is soldering, difference is in the filler material. Soft solder is no good, high content silver solder is used requiring a higher temperature.
    Remember that copper conducts heat extremely well. Oxy Acetylene is the preferred option due to the ability apply a lot of heat quickly, a Butane torch may not get it to temperature or may damage other components as it is a lot slower to heat the required area.


    With 3m of pipe the system will need evacuating and adding of refrigerant, best to get a fridgy involved at the start.

  3. #3
    Join Date
    Sep 2010


    I gave up on the idea of brazing, and used brass flare-unions. Trying to braze without proper tools (just a soldering torch) did not appeal.
    Was a bit of a pain threading the copper pipes through the wall while attached to inside unit, but all working well now.

    This my biggest home DIY challenge to date, but not as hard as feared. Would recommend it to anyone confident in basic plumbing skills including flare joints, and willing do do it slowly and carefully.
    Just avoid old systems using R22 gas. Aside from being less efficient, they are a bad pollutant if you screw up and let them loose.

    Though any sustained leak will cost hundreds to be re-gassed. I decided to invest in a gas sensor from Aliexpress. It is a lot cheaper than a HVAC torque wrench )
    Am just having trouble trusting those copper flare joins not to leak microscopically at 20-bar plus.

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