I'm a guy with no experience in plumbing and could use some advice.

I have a sink with copper supply pipes. The hot water supply pipe terminates at the bottom end in a flare that fits against a bulbous end of the output of a shutoff valve. The flared pipe is held to the shutoff valve by a compression nut. This leaks with water slowly oozing out of the top of the compression nut, i.e., the hole that fits around the pipe.

I tried to fix this by tightening the nut. I tightened a little, then a little more, then a little more, and a little more, until I got scared that I might overtighten and damage something.

So what is to be done to stop the leak?

I could keep tightening it more. That's the easiest solution. Is there some point where I had better stop?

Another solution I've thought of is to loosen and raise the compression nut and put some caulking around the top of the copper flare. Then I could lower and tighten the nut, causing any space between the nut and the pipe flare to be filled by the caulk. But it would have to be some kind of caulk that was not bothered by the heat of the hot water, and wouldn't dry out and crack or crumble. Ordinary silicone caulk might work, or maybe I could use something like one of these:

https://www.lowes.com/pd/IMPERIAL-2-...ealant/3432322
https://www.homedepot.com/p/Hercules...6152/203304169

I called customer support at the company that makes the first product and the lady I spoke to said she thought it would work fine.

Others suggested that I cut off the bottom of the pipe and put on a new section with a new flare and compression nut. That seems a little scary to me, though I understand there are ways to do that these days that don't require soldering.

Any suggestions?

Should I tighten more? When should I stop?

Should I try the high temperature silicone caulk?

I showed the problem to a plumber but he wanted almost $400 to fix this - which seems pretty steep.

Thank you very much.

Alan

 

In all likelihood you need to use 2 wrenches and just tighten it more. Just dont slip off and bust your knuckles.

No you dont use caulk of any kind when doing plumbing.

 

A compression fitting seals with a crush ring..... not a flare.
If you do have a flare..... there may be a crack in the end.

Are you sure it's not coming from the valve stem ?

 

I used to get this kind of leak and absolutely hated dealing with compression ring/nuts till a plumber friends showed me how simple it was to never have a leak many many years ago. Just before threading the compression nut over the ring, smear a thin coating of teflon based pipe dope over the ring. Install the nut and tighten. It will never leak.

 

Thank you to XSleeper, Pjmax and CasualJoe.

I will try these in order of simplicity and see what I can get.

Happy Holidays to all.

Alan

 

I am not sure if you have a compression joint or a flair joint since you describe both in your post, Can you post a picture? Is this and old/new problem?

 

Hello Beelzebob,

It's a pain right now to disassemble this thing for a photo, but here's a diagram of what's going on.
There's a vertical copper pipe coming down from the sink. It has a nut on it and it flares at the bottom end. The flare fits over a protrusion from the supply line shut off valve and connector. You put the flare end over the shut off valve connector, push the nut down over it, and screw it tight. I don't know if "compression nut" is the right term for what this is called. I may have that wrong. But I assume the word "flare" applies here.

The leak is a very slow ooze of water through the top of the nut.

 

An actual picture would be great. From the way you have drawn it, it looks like you should have straight pipe and a compression RING. Not a flare. But maybe it is supposed to be flared. Must be. It's just that usually the nut over the flare is long and tapered. Those flat nuts usually tighten a compression ring into a seat.

At any rate if this is such a hassle, I would be getting a new shutoff and get a new braided faucet supply line.

 

I'm thinking the first thing I will try is CasualJoe's suggestion. It's cheap and easy.

Thanks for your help.

Alan

 

Assuming this is a flare joint, I can think of two issues. 1-The flare angle of the nut and socket are different. 37 and 45 degrees seem to be the standards in the USA.Change the nut or socket to match. 2-- If the angles are the same, there is a burr on the nut and/or socket that need to be removed, A small file or emery cloth can be used to smooth the flair on each part.

 

I'd definitely try to fix it, it's easiest and cheapest.

BUT - if you're still having problems, I'd bite the bullet and just replace with a standard braided hose
https://www.homedepot.com/p/BrassCra...0A-F/100459572

 

My quick fix didn't work and I've discovered more problems with the copper tubing and maybe the faucet itself. I'm just going to replace the whole thing.

Thanks everyone for your interest and advice.

Alan