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  1. #1
    Join Date
    Nov 2010
    Posts
    1

    Default Sweaty pipe in slab hole

    2nd floor washer drain pipe was misplaced in slab and moved during construction to be correctly placed within the wall that is between our dining room and the garage. However, concrete was not poured up against the pipe, and the remaining hole is about the size of my hand, and I can touch the rocks which are under the slab. Initially, a faint smell of mildew existed but no visible water damage. I opened up the wall on the garage side and easily cleaned up minimally damp drywall and mildew. Two plumbers looked at the problem and agreed upon a coupling to "fix the leak". I left the wall open and the pipe continued to sweat the exact same as before the coupling was installed. I noticed the sweating always is at and below the slab level and it was never related laundry frequency. Sweating does appear to be related to the amount of moisture in the ground, i.e. after rains and especially during cooler air temperatures. Also, the hole is warm and humid. Should I just pour concrete into the hole and up to the pipe to prevent the warm air from condensing with the colder air?
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    Last edited by mspadafora; 11-18-2010 at 10:03 PM. Reason: Adding pictures and clarifying info.

  2. #2
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,356

    Default Re: Sweaty pipe in slab hole

    I think that's a good idea. It sounds like moist air is coming up from below the slab and condensing on the pipe. Typically, you don't want the concrete to be in direct contact with the pipe so that if there's any movement it doesn't damage the pipe. You can isolate it by wrapping black vinyl tape (you can get black tape for plumbing at any plumbing supply place) around the pipe.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  3. #3
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,168

    Default Re: Sweaty pipe in slab hole

    Are you sure the pipe is not leaking? The repair they made doesn't look to good. It looks like what they did was use a fernco coupling. One end of the coupling is over the pipe and the other end appears to be over the hub on a 2" fitting. They do not make a coupling for that application. It looks like it is a 3 x 2 coupling tightened down to fit over the fitting. Drain lines don't sweat. You have something else going on there. Try running the clothes washer and check that coupling where it attaches to the lower fitting I suspect that is were you will find your leak.

    John

  4. #4
    Join Date
    Dec 2008
    Location
    Midwest
    Posts
    158

    Default Re: Sweaty pipe in slab hole

    [QUOTE=johnjh2o;228624]Are you sure the pipe is not leaking? The repair they made doesn't look to good. It looks like what they did was use a fernco coupling. One end of the coupling is over the pipe and the other end appears to be over the hub on a 2" fitting. They do not make a coupling for that application. It looks like it is a 3 x 2 coupling tightened down to fit over the fitting. Drain lines don't sweat. You have something else going on there. Try running the clothes washer and check that coupling where it attaches to the lower fitting I suspect that is were you will find your leak.

    John[/QUO
    I agree it looks like they used a 3x2 fernco. and slopped glue all over the bottom hub. Make them remove old 45 elbow and replace with a new one. Have never seen drain lines sweat. After leak is fixed you can pour concrete tight around pipe. The local UPC code does not mandate a sleve of any kind when passing through floor.

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