Yesterday I discovered water stains on one of the air ducts in my house. I went up the attic and saw that a copper pipe cool to the touch which seems to be linked to the condenser? had a pin point leak. (pic at bottom of post)

After googling around, I've seen this can be fixed by brazing it with a torch. I've called around, but none of the local a/c techs seems to work with the plumbing part of a/c's. I have experience in welding and working a torch, but that's about all I know when working with a/c's. I want to tackle this problem myself, but before I do, I've been reading that these tubes are filled with freon or something of that sort.

Can anyone fill me in on what these copper pipes do, how to bleed them before working on them and refilling them back up? What kind of equipment is needed? Any google/search terms you might want to throw my way would be helpful so I can figure out how to do this.


  • 1
    Is it not a refrigeration line? What is the liquid coming out of it?
    – JPhi1618
    Jan 29, 2016 at 20:42
  • Are you sure that's for your A/C? Usually there would be two pipes - supply and return, and usually the control wiring is run along next to it.
    – Steven
    Jan 29, 2016 at 20:52
  • You won't be able to braze or solder anything until you evacuate the line and isolate it. You can't heat it up with liquid in it.
    – ArchonOSX
    Jan 29, 2016 at 20:56
  • The more I read then it might just be a water line then. I thought it was A/C because it was cool to the touch. Nevermind. Might just seal it with some cement. Jan 29, 2016 at 21:12

4 Answers 4


Water spraying from the copper pipe in your photo would indicate a 3/4 inch copper potable water pipe. This can be repaired with only basic plumbing and pipe sweating skills. It may be simpler to use solder rather than brazing copper rod. Either is acceptable, but since you asked about brazing I will answer that first.

You will need a Mapp gas torch with a swirl tip and a copper rod. Both should be available at hardware stores. Start by shutting the water flow off for the pipe. If there isn't a dedicated valve shut the water off at the meter at the street.

Open the sinks' Hot and Cold valve anyplace below the pipe leak. This will drain water and release pressure. Gather torch and copper rods plus a fine wire wheel that can chuck into a drill, fine grit sandpaper, and either a section of sheet metal or a length of aluminum foil. Fill a 1 gallon container with water and place a rag into it.

Start by cleaning the copper pipe wall surrounding the opening. Use the wire wheel chucked in a drill to remove oxidation. When the copper start's to shine brightly switch to the fine grit paper to finish prepping the pipe. Wipe off any dust with the moistened rag.

Last preparation is to place the sheet metal section under the pipe. This will diffuse the flames of the torch decreasing the chance of fire (keep the water bucket close by!).

Hold the torch so that the end of the burning BLUE flame is about 1 -2 inch from the pipe opening. Wave the flame side to side in a 1 inch fan movement. The copper will turn from a bright copper color to a dull red to a dark deep red color in about 20-30 seconds. Keeping the flame on the opening touch the brazing rod to the copper pipe leak. If the metal is hot enough the rod will immediately melt into the copper. You will see it flow onto the pipe surface in a expanding movement. The liquid brazing material will spread to the hottest part of the metal. Remove the flame so that the brazing material doesn't migrate away from the opening. Verify the opening is sealed by noticing if the braze has filled it completely.

Let the pipe cool slowly and have someone turn the water back on. The repair is ready for service immediately.

  • I think you're right on the dot. You recommend solder rather than brazing so I'm gonna take that route. From some google searches, it says soldering and brazing is using metals with different heating temperatures. What type of metal would I use for soldering the leak? Is soldering the same as pipe sweating? Basically just heat up the pipe then patch the hole with the rod? Jan 29, 2016 at 23:42
  • Yes both words are used interchangeably. Shut the water, cut the pipe at the leak so a coupler can be spliced in and sweat with a torch. This is the gist of the repair. I left out details about cleaning and heating.
    – ojait
    Jan 30, 2016 at 0:07
  • What about flux? You need flux to solder copper, and I have always used flux to braze as well. Jan 30, 2016 at 2:40
  • @JimmyFix-it- My first comment stated it was an abbreviated (gist)reply. Besides I just finish typing an hour long answer about the original question regarding Brazing.
    – ojait
    Jan 30, 2016 at 3:05
  • Flux is not necessary when brazing brass or copper with copper rods. For sure when sweating copper pipes with solder.
    – ojait
    Jan 30, 2016 at 3:12

Since this appears to be a plumbing leak, the fix is to shutoff the water, drain it as best you can, cut out the bad section, and solder in a replacement section. The whole process is maybe a 30 minute job and will be much more permanent than any patch you attempt to apply. A pinhole leak in one place may just be the first sign of the entire section of pipe going bad, so I'd replace everything that's easily accessible and showing signs of corrosion. It would also be good to double check the grounding straps in case poor grounding is accelerating any issues.


After looking at the photo, I'm guessing that's not a refrigerant line. If it was, liquid would not be coming out. Follow the pipe, and find out where each end terminates. That will help you determine what this pipe is for.

You do not do this yourself, unless of course you have the equipment, training, and licence to do so.

Before you fix the leak, you'll have to evacuate the system by reclaiming all the refrigerant. After brazing, you'll have to remove contaminants from the line, and then recharge the system. All of which requires special knowledge, and tools.

Any company that installs A/C systems, should be able do this work.


Copper pipe that has started pin-holing should be replaced.

Mineral deposits erode the bottom side of horizontal runs of copper over time. The pipe can become paper thin and even if you successfully soldered a patch into it the likley hood of another pinhole in the near future would make your labor in vain.

Generally the horizontal cold water lines deteriorate first since the water heater captures sediments and the sacrificial diode reduces much of the mineral content preventing the accumulation of the corrosive sludge on the bottom side of the hot pipes.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.