How much length needed for compression connection?


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Old 03-17-11, 08:21 AM
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How much length needed for compression connection?

I posted earlier about replacing 40 year old threaded shutoff valves. Although I haven't yet tried to removed them, I'm concerned they won't unscrew and don't want to risk breaking the inlet pipe off in the wall. I'm thinking a better approach may be to just cut off the old valve and install new ones with compression fittings (I'd prefer not to use sweat fittings).

There is 1.75" sticking outside the wall before the threads start. Is that enough length for a compression fitting? The inlet pipes are chrome plated but I assume they are copper under the chrome. All the water lines I can see in the basement are copper. Any and all advice is wecome.
 
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Old 03-17-11, 01:47 PM
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If forty years is old then I'm ancient. If you have copper piping in your home then the shut-off valves are attached by one of three methods, soldered, threaded adapters (soldered to the pipe) or compression.

It IS possible that you have what are called "drop-ear" elbows inside the wall where the copper pipe is soldered into one side of the elbow and the other side has female pipe threads. The "ears" on the elbow will be fastened to some structure and then a chrome-plated brass pipe nipple comes through the wall and a shut-off valve screws to the nipple. If this is what you have then you cannot use a compression fitting because the outside diameter of the pipe nipple is larger than the equivalent size of copper.

Posting a picture may help one of us to better assess what you have.
 
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Old 03-17-11, 02:19 PM
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Picture link in this reply

Here is a link to a picture: http://home.comcast.net/~lmacmil/IMG_3732.JPG

Although I can't see into the wall, I can feel the threads inside so I must have that "drop ear" setup. I guess I will have to try to remove the old valves. I assume that thread would be a standard pipe thread, right? Based on the nipple diameter, I think it's a 3/8 NPT.
 
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Old 03-17-11, 05:02 PM
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Thats a iron pipe hook-up you have. All you have to do is unscrew the valve and replace it, you can't use a compression on a iron pipe nipple.

Straight or angle lavatory supply kits from the PlumbingWorld

Go down on this link and you will see the type of valve you need, iron pipe by compression.
 
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Old 03-18-11, 09:49 AM
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hi guys Ė

I replaced the same thing some time ago. If I remember I think I was worried like you are Imacmil and I donít remember if I used a pipe wrench to hold the pipe while I unscrewed the valve.

So this is a question for the experienced guys: Does it make any sense to hold the pipe with a pipe wrench while you turn off the valve? Or is that really the only way to do it and that goes without saying?
 
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Old 03-18-11, 09:54 AM
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Yes..you hold the stub with a second wrench.
 
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Old 03-18-11, 10:21 AM
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Gotcha Vic!*********

Thanks!
 
 

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