# How to cap copper water pipe



## Ron The Plumber (Jun 7, 2006)

If you know how to solder, you could solder on a cap.


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## NothingsLevel (Aug 27, 2006)

Where do the water lines come in? From your description, it sounds like they come in from the wall.

When I removed a kitchen sink last winter, I had a similar problem. Wanted to cut off the pipe and cap it above the floorboards (supply came in from below), at least until we had a plumber in to do some more extensive work. The trouble is that as long as there's water in the line near the end, you aren't going to get a good solder joint - the heat from the torch will create pressure in the pipe, and that'll leave you with a hole in the joint. It just will not seal 100%.

I tried a whole bunch of things, then finally a guy at Home Depot suggested a compression fitting. No solder required - just put the compression fitting on the pipe, then screw a plug into the threaded side of the fitting. Took about 5 minutes and solved my problem.


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## Ron The Plumber (Jun 7, 2006)

Here a a trick of the trade, water in the pipe not allowing you to solder a good joint, use a wet vac and suction out the water, then will give room in the pipe for heat to expand to, this allowing the solder to flow and not spit back out of the joint.


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## NothingsLevel (Aug 27, 2006)

A wet/dry vac never occurred to me. I tried using a dowel to displace the water, and then tried some rubber tubing to suck the water out myself. Neither worked very well.


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## Ron The Plumber (Jun 7, 2006)

Stick around will teach you alot of tricks on here. :thumbsup:


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## MacGyver-ess (Sep 27, 2008)

Do you think this would work on the pipes that go to my water filtration system that I want to get rid of? I'm wondering if there is more pressure in my situation that in yours- if it would blow the fitting off?


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## Termite (Apr 13, 2008)

Residential water pressure isn't going to blow a compression fitting off. If you have copper and don't know how to solder, a compression fitting with a threaded cap installed on it is going to be the best method for a temporary cap.

If it is a permanent cap, I'd learn to solder. It isn't hard to do, and you don't need more than about $30 in equipment to do it. If so, start a new thread and we can walk you through it. 

This thread is two years old.


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## micromind (Mar 9, 2008)

Brass compression fittings are pretty reliable at high pressure, I've used them extensively on air compressors at pressures up to 175 PSI, and pretty high temperatures. They work with copper or aluminum tubing. 

Around here, the majority of plumbers use angle stops (the shutoff valves under your sink) that are compression connected to the 1/2" copper pipe sticking out of the wall. 

I've done the compression fitting with a pipe plug screwed into it for a cap as well, and had no problems. 

Rob


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