Compression fitting leak

[Stormin Mormon]

Under my trailer, some 1/2 inch soft copper sprang a leak. It's not in a great place for working. I called the trailer park, and they sent thier man out to shut off the water. I cut out about a foot of tubing, using a tubing cutter. I sanded the ends of the tubing, using some sand screen. I used two compression unions to put the new tubing in. Well, hours later one end of one fitting is dripping, about one drop a second.

I tried tightening the fitting down a little harder, and it's still dripping. Any good old country wisdom for stopping a compression fitting from dripping?

[news]

easy, just go to the hardware store, buy a small bottle of pipe thread dope....use it on the threads of the compression fiting.....it is not for sealing, but rather for lubrication of the threads....you will be able to tighten the nut a full turn or more with the lube....it is amazing how dry brass threads bind up...

[tom]

Keep tightening? Tom

[Big_Jake]

I seem to get more leaks when I sand it then when I don't. I know you are an HVAC guy, why not solder it together with refrigeration couplings?

JK

[Stormin Mormon]

Actually, that's my next step. I've got some more tubing. It's just in a challenging spot, and there's fiberglass hanging from above that gets on me.

Old copper, I find stick braze works better than solder. For whatever reason, solder is less likely to seal old copper.

[Stormin Mormon]

That's the easiest answer.

[Stormin Mormon]

I did spray the fitting with WD-40 before tightening. Might need thread dope, or some grease on the threads to slick it all together.

[Mortimer Schnerd, RN]

I don't sand. You may need to get a new fitting and slide a new ball over the end of the tube. Before I did that, I'd try taking the fitting loose again and then wrapping the threads with teflon tape, then retightening. I always used teflon tape for compression fittings... both stainless and copper... back in the day when I was maintaining a scuba fill station. If it didn't leak with

2500-5000 psi of air behind it, it won't leak with 50 psi of water either.

[professorpaul]

My best results have been when I used steel wool (no "digs"), then coated threads and mating parts with Si. grease. Use two wrenches to dog the fitting down.

[Jeff Wisnia]

I've had success twisting teflon pipe thread tape into a "string" and putting about two turns of it around the pipe adjacent each end of the ball.

Easy to see why that works once you think about it.

Jeff

[tnom]

Is the ferrule slid onto the tube fully? Is it compressed symmetrically?

[Paul Franklin]

I always coat the compression ferrule and the fitting threads with rectorseal (sp?) pipe dope before assembling and tightening. This lubricates and seals at the same time. I've never had one leak since I started doing this.

HTH,

Paul F.

[Mortimer Schnerd, RN]

Ferrule... that's the word I couldn't think of when I posted my last response. If he has any doubts at all about the integrity of the tubing ends, he needs to recut them, slide the nut on each end, then the ferrule until a little bit of tubing pokes out... maybe a 1/8" or so. Then with teflon tape on the male threads of the fitting, put it together and torque it down using two wrenches in opposition. The ferrule will slide within the compression nut to wherever it needs to be as it's tightened down and will deform within the fitting to seal itself as well.

[Stormin Mormon]

That's a good thought. I'll try teflon on the threads, and then crank it down. Or, maybe I'll cut that all out, and silver braze in some new tubing. The silver braze is more work, but more likely to last.

[Stormin Mormon]

Is the ferrule slid onto the tube fully?

CY: Yes, it should be. I pushed the tube good and hard into the end of the fitting.

Is it compressed symmetrically?

CY: I don't know. Since I don't have X-ray vision, I'm not sure how to tell.

[Stormin Mormon]

That could be the answer. I've thought they went on with a shot of WD40 for lube, but rectorseal might do the job, too.

[kool]

You must have a flaring tool. Use a flare union.

[CJT]

I thought all those HVAC guys would, following their own advice, call a professional plumber ... and that business was so good they didn't live in trailers.

[tnom]

Take it apart and see if it crimped equally.

A compression fitting on such a low pressure system should seal without any problems. It should never need any tape of sealant.

If your install is leaking then the tubing is scarred or cracked, the fitting is defective, or most likely you introduced grit into the ferrule which prevents it from sealing.

[Tekkie®]

Big_Jake posted for all of us...

He is no HVAC guy he's a hack.