Copper pipe goo

[Nolte919]

The other night I found a copper pipe in our house leaking with a very fine spray. There was also this white goo around the leak that looked like silicone without the stickiness or the smell. I wiped it off and cut the pipe at the leak with one of those pipe cutters you spin about the pipe. It wouldn't quite cut all the way through the pipe so I finished the job with a hacksaw. I put a coupling on and no amount of solder would keep it from leaking. The next day I bought more couplings and cut the pipe 3" on either side of the leak and soldered in a 6" piece of pipe with no leaks at all. I'm far from a expert but I can sweat copper pipe.

So my questions are many. What caused the original leak? There was no other metal touching the pipe which might cause a leak through electrolysis. And what was with that goo? Where did that come from? It looked like silicone. When I cut the pipe why couldn't I solder on a coupling? I've never had a solder joint fail. It's amazing how foolproof it is. I'm seriously worried. This leak occurred on a vary convenient stretch of pipe. What happens when the next leak is inside a wall? Is there goo flowing through the pipes through which my family drinks?

I can not thank you enough for any advice.

 

[Fmkehoe]

I have no idea with the goo is, but every now and then copper pipe does fail. Sometimes it’s just a oozing drip, so the leak might be microscopic, sometimes it’s a little bit bigger like yours, a spray.

 

[Helper Dave]

Was the goo coming out of the leak, or was it on there like someone tried to "fix" it by pasting over it? If it was coming out, did you notice any more in the pipe you cut out?

As for the leak, lots can cause it over time. Sediment, turbulence in the pipes, etc. So it's tough to say case by case.

Then, when you soldered, was there water in the pipe yet? That's the biggest culprit for not getting a good join. If it's steaming when you're heating it, it won't get hot enough. Or was the pipe not smooth and clean?

 

[havasu]

Then, when you soldered, was there water in the pipe yet? That's the biggest culprit for not getting a good join. If it's steaming when you're heating it, it won't get hot enough.

This!

 

[fixitron]

The only leaks in copper pipe that I have ever encountered (which is a lot) were either from someone putting a nail or screw into it (in a wall), from a freeze or from water that was acidic. Most of the time the piping was type 'M' (the thinnest wall). Yours sounds like it is from acidic water. The leak could have started as a tiny drip, allowing an eventual buildup of slime. I imagine that when you tried to cut the pipe the cutter pushed at least part of the pipe in so that it was no longer round. I have encountered such leaks (from acidic water) where I could crush the pipe with 2 fingers, because there was so little of the copper wall remaining. I have very rarely encountered such leaks in type 'L' pipe.

 

[Aloha Mark]

There are also calcium deposits which can collect over time. Every public water system in the US has some form of sediment endemic to the location and the type of water tank/reservoir used. Animals like frogs and toads can also get into the system. Private wells have their own quirks, unique to the water table where a pump draws water. Whole house water filters may or may not help. They have their own downside (such as leaks, and bacteria buildup).