My heat pump compressor has a pinhole leak on one of the small lines of the reversing valve assembly. It's small enough that you can't see it, but I could hear it hissing after the system shut off, and I could cover it up with my finger.

The problem is that the leak is very close to the factory brazing joint on the reversing valve assembly, and the line that has the leak is only about 1/4" diameter.

I thought about taking a torch to the line and trying to slather solder all over it, but I was worried about heating up the nearby factory joint brazing, so I had the local HVAC outfit come out and take a look at it. The tech basically said he didn't want to do it, due to the possibility of making things worse - and now I got their $100 mandatory "diagnostic fee" bill sitting on my desk.

Presently I purchased a very small high-heat butane torch that looks like it will get pinpoint heat right on the hole, so I should be able to get solder over it and be OK so long as I don't heat up the line enough to affect the factory joint braze. I can't think of any way I can keep the nearby joint cool while still heating up the small pipe enough to accept solder.

My dad seems to think I should slather the leak area in an industrial two-part ceramic epoxy that's designed for marine piping. I imagine that would work, but I don't like doing "improper" repairs and it would always bug the shit out of me knowing that the epoxy could fail again.

Obviously the system will need to be evacuated and recharged once this is done, but I'm looking for suggestions for how to seal up the leak.  Throw it at me.

edit: for visual learners, see the approximate leak location below

I believe that you need to evacuate the system and then fill it with nitrogen so that it doesn't cause corrosion inside the pipes when you braze it.  

So, how did the AC tech think it should be repaired?

I would remove refrigerate, purge with nitrogen, heat the area till the filler starts to flow then remove the heat and let cool and then pressure test it.

One of the problems is the little line is a needed to operate the valve. Too much heat and you could fill the line with the brazing material, as it will flow to the heat, it doesn't take much to fill a line that small. I have seen a 1/4" line filled before

Edited to add. The brazing filler melts at over a 1000 degrees, so MAPP gas or acetylene will be needed

Unfortunately I was away for work, he spoke to my wife. As she recalls he basically said he didn't think he could braze it without disturbing the factory joints of the reversing valve, so he didn't even try.

Said something about the system not worth being repaired, as it was "pretty old" (again, 2005) and all sorts of other stuff would start failing eventually. Basically wanted to sell a new system is what I'm getting from her.

The system overall is in great shape, I have troubleshot and repaired failed components of the compressor (defrost board and reverse coil went out, replaced worn contactor) and air handler as they've occured, using better quality replacement parts.. But fixing leaks is something I'm not up to speed with.

It seems like something an experienced tech should be able to repair without pussing out? I dunno. The HVAC outfit we had out here have always been great in the past when doing my parents' furnace work. It annoys me because this is the first time I've ever had to call a repair company for anything since I became an adult, and it didn't get me anywhere.



The leak is so small that I can't see it with my bare eyes. I could plug it by touching the face of the small 1/4" line, but even looking up close, I can't see it. It was large enough to drip some oil down to the larger pipe below.

At one point it made an audible hiss.. But that was about a week ago. System holds around 5lb of R-22, so... The compressor has been shut off since the leak was found.

Yes the line will need to be filled with some type of inert gas like nitrogen in order to accomplish this.  So do you have a pump to evacuate and then refill the lines once you're finished?  If so, and again I'm not an expert on brazing, but if you can keep the flame very localized with some type of attachment, keep in mind that 1/4" line will heat up in no time.  I mean by the time you apply the heat, wait a few seconds and you should be able to put the brazing rod on the leak to fill.



As for the guy who came out, 2005 is not old.  He just wants to sell a new system.  You could always try and find someone else who is willing to make this repair.

Get someone that knows what they are doing. What  jamie930 says needs done but if the person who does it has the proper tools then they can save your Freon and reuse it saving you a good bit. I would also use wet rags torn into strips and rap around the other parts of the valve to keep from messing up the smaller line. Its a pain but doable..

heat paste, wet rags Oxygen acetylene torch 15% silver solder, evacuate and fill system with dry nitrogen and a steady hand to solder that small of cap tubing. I can do it in my sleep but I know a lot of techs don't have those skills.



a picture of the valve itself would be helpful, usually when the cap tube leaks it is because the copper is exposed to sulfur from well water and in that case it's just a very high priced bandaid till the next leak in a short time

OK the nitrogen gas business is beyond my means at this point.

It sounds like I need to get a competent tech back out here.

Frankly I don't even want to pay their "diagnostic fee" given that the tech drove out here and promptly gave up.

Same company that we had out here before confirmed, they want $2200 to replace the reversing valve assembly. I can find the replacement valve on eBay for $90 so I'm not sure where they get $2200 in markups, that doesn't seem to cover labor and refrigerant cost, but what do I know?

I'm in the process of getting other quotes. Apparently the tech evacuated the system and purged with nitrogen, so I may be able to just try and do it myself.

Just use a smaller torch tip.
Make sure the nitrogen is flowing without any real pressure buildup.
Copper oxides are not a good idea in a refrigeration system.
The flakes end up in the worst places (like orifices and TXV valve seats).

Stay silv brazing rods are your friend here.
The self flux with the phosphorous they contain (about 5%).

I got some self-fluxing silver solder. I don't really need to worry about it getting into the 1/4" line since the hole is not even visible, right? I don't know how it would even get in there.

Precisely where the red circle is in the photo above. Just above the lower bend where it meets the larger tube - can't see the crack itself but when I briefly aimed a torch at it you could see the refrigerant escaping, and you could hear it and plug it with your finger.

That being said I don't know what the deal is.. I've started calling other HVAC outfits and just flat out asking for a quote on how much it would cost to replace the entire reversing valve assembly and recharge the system.  Not a single one of them will give me a quote over the phone without sending someone out first to do their $100 "diagnostic service."

Look, I understand you don't trust the customer to provide a diagnosis, but damn... Just give me a ballpark figure.

It can be cold soldered. Don't heat the metal all of the way. Melt the solder and it will stick over the leak. Won't be pretty but it will work

Yeah I tried applying silver solder using butane torch. Solder stuck but fell right off when I flicked it a bit with my finger.

Is rosin-core solder proper to use on a copper line such as this? Can I actually apply it with an iron?

I'm also considering just slathering on the industrial epoxy and having the system recharged once it cures.

Jesus Christ. Epoxy?  It will blow off. And the oils in the lines will slowly eat at it. Back to square 1.

Get a pro if you think epoxy will work. Or replace it.  That's why homeowners shouldn't mess with this stuff.

acetylene torch with 45% silver solder and stay silv flux. Sand it very good apply flux, heat, solder, cool.  Heat quick. Get in and out don't stay long enough for the heat to transfer to the copper to brass joints. Wrap valve with wet rag prior.


Actually, I'd use stay silv 15% braze. Sand it good, no oils etc, then  Heat it, apply braze, let it flow out decent. You'll pop out the line where it's silver soldered though most likely so be carefull.  Nitrogen is recommended but if it has a filter drier don't worry about it.  It's so small, barely any scale will be made.

Christ man, the guys here told you what type of brazing rod to buy and you're using solder?  That didn't work now you think epoxy will hold?  These guys are giving correct advice but you're not listening and/or still want to do it your own way, in which case, have fun.  Let me know how that epoxy holds up to refrigerant state change.

time for a new valve, you nessed up

I think he said that the company that came out to look at it recovered it and his system is empty.....or maybe I misunderstood.