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cap underground copper pipe

Posted by ionized (My Page) on
Sat, Jan 29, 11 at 23:03

How does one cap a buried copper pipe? I have underground pipes to my detached garage. The pipe branches underground for sink, toilet and there is a branch to a tap in the middle of the yard. The last one has to go. I dug up some parts of the pipes today. They look to be pretty rough from corrosion on the outside so soldering a cap on them looks like it will not be possible. I have not yet tried a wire brush or anything like that.


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RE: cap underground copper pipe

Even though it looks rough, copper will clean up rather easily, however, you should know that code prohibits any dead end pipe greater than 12" in length. To cut and cap that line you need to go back to the source where that line ties into your system and cut it within 12" of the tie in point.


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RE: cap underground copper pipe

Thanks, lazypup. I will get out there today with a wire brush and see what happens. The pipe looked pretty "knobby" in the failing light last evening. The soil is very moist and the pipes may have been there for 40 years. In your experience, a standard cap will fit. Is there any other solution that I need to have on tap if the fit is not good enough

Is that 12" rule for underground pipes or any location?


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RE: cap underground copper pipe

I would suggest you determine where you want to cut the pipe, then use a stick and a wet rag to remove the dirt from the pipe at least 3 or 4 inches either side of your cut line.

Once you have the majority of the dirt off get a strip of emery cloth about 2" x 10" and loop it over the pipe, then grip both ends of the emery and pull it back and forth like a shoe shine rag until the pipe is clean.

Once you have the area clean use a tubing cutter to cut the pipe. Now clean the end of the pipe once more with the emery, apply flux and solder.

If you do it in that manner you will minimize the risk of getting the pipe out of round which would make it difficult to fit a cap on.

Copper tube and copper pipe standards have not changed so is you have a 3/4" pipe thats 40yrs old it is still the same size as a new 3/4" fitting.

Now I know this answer is going to open a can of worms but code prohibits any dead end pipes in the water distribution system because the water standing in a dead end pipe is stagnant and bacteria could form there. Code allows up to 12" to permit installing "field manufactured hammer arrestors".


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RE: cap underground copper pipe

Thanks, I've done that kind of buffing routine before. That sounds like excellent advice to polish the pipe before cutting. I love this place. It is raining today so I probably won't attack the problem until next weekend.


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