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Old 10-04-2012, 09:46 PM   #1
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What's this length of CPVC for?


I broke the cold water cpvc pipe removing a cabinet and need to repair it. Is this length of 3/4 pipe needed? I was just wondering if it served some sort of purpose or if it was (more than likely) some kind of 'oops, we don't need that 3/4 pipe to go any further, let's cap it'.

Thanks......
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Old 10-04-2012, 09:54 PM   #2
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What's this length of CPVC for?


Was it connected to the water supply? If it was then it was probably there to act as a water hammer arrestor. It fills with air and absorbs the shock.

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Old 10-04-2012, 10:03 PM   #3
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What's this length of CPVC for?


look at other side to see if they did the same thing....could be arrestors as mentioned....
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Old 10-04-2012, 10:11 PM   #4
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What's this length of CPVC for?


Well I don't want to rip out any more drywall......

So assuming its an arrestor, I guess I can just glue it back on to a T piece?

But now this 'arrestor' topic begs another question- do I need this on my shower and bath outlets I just plumbed out of a new shower valve. I've never seen this type of thing before.......
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Old 10-04-2012, 10:30 PM   #5
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What's this length of CPVC for?


My house was built in 1996. Sounds like these things aren't really needed, but I'll glue it back in just the same.

http://www.pmmag.com/Articles/Column...00f932a8c0____
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Old 10-05-2012, 12:38 AM   #6
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What's this length of CPVC for?


I know a lot of these things are regional....but......

This seems as a clasic example of why to not use PVC.....had it been copper, I really doubt you would have broke anything.....

With that said....It looks like the feed line (cold side) is 1/2"....and that pipe is 3/4" that goes to nothing? If so....I would call that the 'poor mans' version of an arrester....and, if it works...hey...simple is better.....so....seeing how most plumbing guys don't want to spend more money than they need to, it looks like an eligant way to solve water hammer problems (as long as it never leaks air out)
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Old 10-05-2012, 05:39 AM   #7
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What's this length of CPVC for?


Looks like you used an ax to to open up that sheetrock wall instead of a drywall saw, ossilating saw, at least a razor knife, so that rocks going have to be cut out and replaced anyway.

Why is there no vaper barrier on the insulation?

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Old 10-05-2012, 06:44 AM   #8
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What's this length of CPVC for?


Joe, that's just the cold and hot water feeds for the faucets that will be on a cabinet counter. Not sure why a vapor barrier would be needed there. Yes, I punched a hole in the drywall to get to the problem quickly! I will be cutting it out as a neat square come repair time.

But back to the poor man's water hammer arrestor- do I just need to glue on a T to connect that 3/4 and 1/2 together? I guess I don't understand how that could serve any function since the whole line would be filled with water anyways.
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Old 10-05-2012, 06:56 AM   #9
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What's this length of CPVC for?


That empty chamber will not fill with water unless someone removes that cap.
What's better, removing it and find out after it needed an arrester and have to go back and open up the wall or have it in place doing no harm?

Those are most often seen used at the end of a line.

If you look at some of the older post in the plumbing area your going to see dozens of people trying to deal with the pipes slaming anytime the water gets shut off.
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Old 10-05-2012, 07:15 AM   #10
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What's this length of CPVC for?


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Why is there no vaper barrier on the insulation?
Could be an interior wall.
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Old 10-05-2012, 07:22 AM   #11
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What's this length of CPVC for?


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Originally Posted by md2lgyk View Post
Could be an interior wall.
It is.
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Old 10-05-2012, 07:25 AM   #12
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What's this length of CPVC for?


Quote:
Originally Posted by joecaption View Post
That empty chamber will not fill with water unless someone removes that cap.
What's better, removing it and find out after it needed an arrester and have to go back and open up the wall or have it in place doing no harm?

Those are most often seen used at the end of a line.

If you look at some of the older post in the plumbing area your going to see dozens of people trying to deal with the pipes slaming anytime the water gets shut off.
I guess I don't understand what I need to do to put it back the way it was before I cut it out and threw away the old parts. That 3/4 piece that is left looks like a hollow pipe with a cap on it. Not sure how to make that part hold air.
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Old 10-05-2012, 09:53 AM   #13
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What's this length of CPVC for?


Quote:
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I guess I don't understand what I need to do to put it back the way it was before I cut it out and threw away the old parts. That 3/4 piece that is left looks like a hollow pipe with a cap on it. Not sure how to make that part hold air.
When you recharge the line, air will trap in that pipe extension and work like a shock absorber. Air compresses and water doesn't so the hammer action will stop at the riser. The air will eventually be mixed into the water though after a long period of time.
Real arrestors are available that are built into the angle stop and are installed in your cabinet if you want to eliminate the riser.
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Old 10-05-2012, 10:22 AM   #14
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What's this length of CPVC for?


I guess I still don't understand the physics behind this. It seems logical that after I glue on a new T and then turn the water back on, that the water will flow up into the length of the 3/4" pipe.

Are you saying that an air pocket will persist in the 3/4" pipe after I turn the water on?
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Old 10-05-2012, 10:48 AM   #15
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What's this length of CPVC for?


Yes, over a long period of time the air will mix into water though. Then if you drain the water down it will pocket air again

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