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Can a VERY slow leak be fixed or do I need to re-sweat?


tlogan's Avatar
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02-21-07, 09:35 AM   #1 (permalink)  
Can a VERY slow leak be fixed or do I need to re-sweat?

Title says it all.

I'm finishing my basement and adding a bathroom. All copper work is complete, EXCEPT....at the connection to the shower mixing valve, a VERY slow leak has appeared. I can't see it form and I've never seen it drip, but when I touch the bottom of the connection there is definitely a drip there. I can see a small spot on the bottom plate where it has dripped. I soldered a female connection to the copper line, then used teflon tape on the male end, tightened the connection but apparently not quite enough) and then soldered the copper line to the rest of the run.

Is there something I can use to stop the leak or do I need to try to re-sweat it? If I need to redo it, can the soldered joint that I need to undo be re-done without cutting everything out and making/running a new piece?

Thanks for any advice!
Tom

 
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02-21-07, 11:03 AM   #2 (permalink)  
It might seal itself after a period of time. Of course that "period of time" may be measured in months, many of them. And then there is no guarantee that it won't commence to leak again sometime later.

You really need to unsolder this joint and re-do it. When you unsolder, use a cotton rag (no synthetics) to wipe off the solder on the pipe. Clean the pipe thoroughly with fine sandpaper or a Scotch Brite pad. Liberally flux the pipe and use a new (properly cleaned) fitting. Heat the pipe first and then the fitting. Touch the solder to the joint with the torch flame held away from the joint. If the assembly is hot enough the solder will be "sucked" into the joint and flow all around. If the solder is not drawn in then the joint is not hot enough or else it is not properly cleaned and fluxed.

 
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02-21-07, 05:33 PM   #3 (permalink)  
Posted By: tlogan . I soldered a female connection to the copper line, then used teflon tape on the male end, tightened the connection but apparently not quite enough) and then soldered the copper line to the rest of the run.

Tom
If you got your teflon joint too hot when torching at the next fitting, maybe the teflon tape melted out somewhat, and that is why it now leaks. Because the teflon tape that gets built up actually stops a person from tightening a fitting as much as what could be...especially if one goes round the pipe several times with the tape. Then this becomes your enemy when after you think you have a tight comnnection, then heating the pipe too hot in that area can probably make the built up tape shrink out of the threads.

I have gotten paranoid of sweating copper near threaded joints for the very reason you gave. I prefer, whenever possible, to have the connections closest to the threaded fitting already presweated so torch heat does not expand the threaded joint, and cause a similar leak.


Recently under a mobile home, I only used pipe dope, rather than teflon tape out of this fear. And I actually heated up the female fitting SOME to actually intentionally expand the female fitting so I could actually tighten the male threaded fitting with the dope on it, even tighter. And then when it cooled it shrunk and made an extra tight connection. I didn't want to go thru what you are, because I get real angry over stuff like this because it's a big waste of time having then to shut off the water, try to drain all the water out, and then have to cut up your work and redo it.

Just so you know, here is some practical theory: In heating up either a nut, or a female fitting,... the female part expands more than what is inside of it (copper male fitting or say evena bolt). That is why you want to only heat up the female receiving piece. That allows you to be able to loosen seized/rusted bolts from nuts, or to loosen male galvanized fitting from a female fitting. And in my case that I cited above, I used this principle to work for me, when actually putting it together, rather than in takiing it apart.

 
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02-22-07, 07:21 AM   #4 (permalink)  
Thanks for the replies. I found some black wrap with a sticky side that is supposed to stop this kind of thing. It streches really long and then you wrap around and as it shrinks back it tightens up around the pipe and sticks to istself. I'll see if it actually worked when I get home tonight. Would it pass an inspection?

DaVeBoy -

I did this for both sides of the mixing valve....
I solderd the female end to a length of pipe, let it cool, then measured out to the pipe it needs to connect to (coming down from the ceiling) and cut it. THEN I attached the female end to the valve, cleaned and fluxed the ends of the pipe, cleaned and fluxed an elbow, then fit together and soldered at the elbow.

Didn't think melting the teflon would be an issue, but it is only about 4 inches from the thread to the elbow, so I guess it's possible.

Tom

 
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02-22-07, 09:42 AM   #5 (permalink)  
I follow what you said. Yet the fitting leaked anyway. That is why I know people who use both teflon tape AND dope, together. A master plumber I know (he is the brother in law of the main guy I do maintenance work for/owns plumbing store.) does this. He said that since he started this, he has no more thread connection leaks.

 
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03-05-07, 02:03 PM   #6 (permalink)  
Update to this fix

Just thought I'd update what I finally did to fix this....

I applied the pipe wrap as I mentioned earlier. Noticed over the past week that it began to feel wet on the TOP of the threaded joint where the tape was. So I guess the tape was failing as well.

It was bugging the [email protected] out of me, so I just went ahead and re-did it.

First, I cut the 1/2" copper line that feeds the valve, leaving about 6" above the elbow. After removing all of the bracing for the mixing valve, I had enough wiggle room to unscrew the elbow piece from the valve. After cleaning everything, I applied new teflon tape to the threaded end (I went around 5 times, since I did three the first time and wanted to only have to re-do this once). The connecting piece still looked solid, so I thought I'd try re-using it. I threaded it back on to the valve, and of course the cut ends matched up perfectly. I had a 1/2" slip connector on hand. I re-shined the ends, re-fluxed and then re-soldered. It only took me three tries to get all of the water out of the line, but the third time was the charm. Re-attached the valve to the bracing, turned on the water and now good to go. Dry and solid.

And surprisingly enough, I didn't really get wet. I learned to keep a rag handy and as soon as the hack saw cuts through the pipe and water starts spraying, just throw the rag over the saw and it at least keeps the water somewhat controlled until you get all the way through and can get a bucket under it.

I guess the lesson is it's best to just re-do the problem area.

Thanks for all your help!
Tom

 
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03-05-07, 04:49 PM   #7 (permalink)  
Thanks for posting back. Success. Great news.

 
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