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A 30 year old building has a history of slab leaks and has been repiped. The final line in the slab has begun leaking.

Repiping involved piping in the attic: I want to minimize the probability of a leak for obvious reasons.
What is the thought process to decide whether to use PEX, PVC or CPVC?

I talked to a plumber's wife, who indicated he prefers PVC over PEX for repiping.

2 Answers 2

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First off, I'd be discussing this with the plumber, not his wife. Since the final line being replaced is the cold supply, any one of the three could be used. Since it's being installed in the attic and probably running down walls, I think the PEX is your best bet. You can run it from point to point without any joints. We've all seen PVC leak from time to time and running it in an attic could expose it to cracking if anyone's up there moving around; they'd be less likely to damage the PEX. This might be considered to be an opinion based question so it could get bounced.

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  • I agree with jack pex can actually handle freezing where cpvc tends to shatter , I am not saying pex can Handel all freezing but I have seen it almost 1-1/2 times it’s size full of ice and it did not leak, (the reason pex was there because the cpvc froze the year before and took out a large section of ceiling. Putting the pex under the insulation keep it from freezing in that attic.
    – Ed Beal
    Sep 15, 2020 at 13:45
  • @EdBeal. It is possible to freeze in North Florida: a 1984 freeze burst copper pipes. Not sure if it makes sense to insulate or just let the water trickle to prevent the rare freeze
    – gatorback
    Sep 15, 2020 at 16:13
  • Ok I was providing my experience I don’t like plastic pipe under insulation, I have broken a few doing remodels so I put the pipes on top but the pex is flexible so after a freeze I thought why not keep it warm. I won’t kneel on it and break it. Water trickling works if you remember.
    – Ed Beal
    Sep 15, 2020 at 16:19
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On my morning dog walk I have had some conversations with a plumber working on a total slab up rebuild of a burned house. All copper water lines below the slab are being abandoned. The new water lines will be PEX.

He is bringing the cold water main supply into the house through a conduit of PVC Schedule 80. Looks like 3 inch, but I don't really know. He hired laborers to tunnel under the slab to a front half bathroom. There is a horizontal run of this PVC from a few feet outside the slab then a long sweep elbow to a vertical run of PVC coming through a hole in the slab. He fed the PEX line through this conduit. From there all piping will be in the walls, inter-floors space, and attic.

Should the incoming water line ever leak, one could pull the leaking line out and feed a new PEX line in.

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