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Thread: sub-concrete floor pipe leak ?

  1. #1

    Default sub-concrete floor pipe leak ?

    I have a basement bathroom.. I was putting in some new flooring, and the old vinyl was really moldy on the bottom when I took it out. after drying the bare concrete floor, i noticed there was still a damp spot. I did some wet testing by pouring water into the sink drain and the shower drain, and it the damp spot appears after I do this. The plumbing is below the concrete floor, so I suspect there is a break in the abs pipe that is allowing water to come back up through the floor ?
    The pipe on the right is the sink drain, and it goes through the far wall and into/through the concrete floor at the middle of the wall (as shown).

    dunno.. Will post a pic.. Can anyone tell me how the toilet, sink and shower plumbing will look below the floor ? I guess I'm going to have to break open the concrete floor to have a look, but I want to minimize any additional damage.



    Any other ideas / approach ?
    Last edited by bobmac; 08-10-2008 at 04:46 PM.

  2. #2
    General Contractor Carpenter toolaholic's Avatar
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    From what You've said,and asked, I don't think You're qualified, to handle this one. Best advice is to call a plumber

  3. #3

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    Quote Originally Posted by toolaholic View Post
    From what You've said,and asked, I don't think You're qualified, to handle this one. Best advice is to call a plumber
    thanks for the insight toolaholic, alas, i decided to post on a plumbing forum instead. Anybody else have an idea of what the leak problem might be ?

  4. #4
    General Contractor Carpenter toolaholic's Avatar
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    You can rent an elec. jackhammer and bust up the floor. plumbing waste and drains will be directly below the concrete, Then run water again to find leak and repair. test plugs for toilet and shower and other fixtures down stream will give You a better shot at seeing the leak. At least You'll save some $$on the bust up ,if You bring in a plumber. Report back after demmo

  5. #5

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    A partner saw (concrete saw) will help in getting a clean break and not tearing up more than you have to.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default leak

    Have you ever heard that water runs downhill? If so, and if the drainline is not obstructed, how is water from a leak in a drain pipe under the floor going to flow uphill, through a concrete floor, and show up as a wet spot?

  7. #7

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    i dunno.. if the drain/discharge pipes are encased/semi-encased in the poured concrete floor, and the pipe has a leak, and the floor has a crack, then its possible. In the picture, all of the discharge/drain flow is from left to right (even though the sink drain source is to the extreme right, it is plumbed back to the left to about the middle of the wall, then into the floor). The sewer main flows out to the street, which is to the right (left to right flow) The wet spot is 'down stream' of all drains entry points..

    In fact, the area in question is not the nice smooth concrete as the perimeter of the bathroom floor is - maybe the floor has been opened up before, patched, and not smoothed out like the original floor.. Maybe the bathroom was only plumbed for a toilet and sink, and someone decided to plumb in a shower drain after the floor was already poured ?

  8. #8
    General Contractor Carpenter toolaholic's Avatar
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    Bob ,when we test a new,or have changed a D.W.VENT system ,We test for leaks. Pick up some test plugs,and test ! Do a search Here or elsewhere.

  9. #9

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    Quote Originally Posted by toolaholic View Post
    Bob ,when we test a new,or have changed a D.W.VENT system ,We test for leaks. Pick up some test plugs,and test ! Do a search Here or elsewhere.
    Yeah, well I wish the previous owner had done a test prior to pouring the concrete.. Maybe they did, and its since sprung a leak.. dunno. I think, in essence, I've done a 'visual' water test - I'm drying the damp area, and I'm going to wet test all three sources individually. (toilet, shower, sink drains), hoping that might tell me something about the sub-floor drain pipe configuration. film at 11..
    Last edited by bobmac; 08-31-2008 at 09:59 AM.

  10. #10

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    so, we were away for two weeks on vacation.. i turn the main water supply valve off when we're away from the house that long, just as a precaution.

    prior to leaving, the subfloor was dry, and i couldn't get the spot to re-appear by wet testing the 3 drain pipes.upon return. hmmm. upon returning, i have a look at the same concrete floor area, and its damp again..

    so now i suspect a foundation drainage problem.. different beast..

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