Slab slightly wet / darker color

Old 07-15-18, 12:22 PM
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Slab slightly wet / darker color


I recently had a copper pipe leak in our bathroom and had someone do a repipe with pex do prevent future problems.

Right after I finished closing all the dry wall, I noticed that in the bathroom, right where the sink used to be (opposite side of the leak), there is a wet/dark spot on what appears to be the foundation. I opened the drywall again because I figured I must have drilled a screw in the pex, but everything seems fine.

The wet spot seems to be by a drain pipe. There is no smell whatsoever from what I can tell. It's hardly wet, this morning I could feel it and I had to feel multiple times to be sure it's not just dark. When I opened the drywall, the dust from cutting it went over the spot and now it doesn't feel wet anymore, but still looks the same.

I don't think it used to look like this, I think this is new.

When putting my hand in that opening in the wall on the picture, I cannot feel any wetness whatsoever around the pipe or on the wood, no where.

What are possible explanations for this, and what would you do to proceed before jackhammering the foundation open?

Thank you
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Old 07-15-18, 02:02 PM
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Do you have a thermal camera or can borrow one? One look at it with a thermal camera will tell you if it's wet by it's cooler temperature. You can also try running water and look carefully inside the hole and around the pipe for any sign of water.
Old 07-16-18, 10:14 AM
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It looks more like a stain than wetness to me... but it's always hard to tell.

A moisture meter should be able to tell you as well. You'll just compare the moisture at that point to a few feet away.

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