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Thread: Cement slab leak

  1. #1

    Default Cement slab leak


    I have found a VERY slow leak in a 3/4 line that supplies cold water to two bathrooms in my home. The lines all pass through the cement slab for my Texas, ranch style home.

    I'm assuming this line is the feeder since it goes into the header and all the other lines that are soldered to the header are 1/2 (everything is copper).

    I haven't found the header that feeds this 3/4 line yet. So far I have only opened the wall behind the wash machine. My next target will be behind the water heater.

    All the copper lines are inside a hard plastic pipe (liner?) which goes about 3 inches above the slab. Then I have about 13 inches of copper until I hit the header.

    The only way I can tell the 3/4 line is leaking is because the plastic liner on that line is full of water and there is a very minimal wet area where it leaves the slab. We found the leak after there was a wet spot on the carpet by the header. After opening the wall, everything dried out.

    Question 1) Is there a universal spot these main headers usally are?
    Question 2) Is there an easy way to identify a soft copper line?
    Question 3) Once I find the supply, and assuming that it is soft copper, should I be able to solder new pipe to an end of the buried header and pull the old out as I pull the new in?
    Question 4) Are there any tools that can help me do this? Special winches, some sort of thingey I can grab the old pipe with to pull on, etc?

    I REALLY don't want to climp up into a 4 foot attic during a Texas summer!

    I have run hard copper lines and am OK with soldering joints.

    Many Thanks for any insights you can share.
    Texaro - bkryzer@yahooo.com

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    2. NO
    3. NO
    4. NO

    Sorry to rain on your parade, but nothing easy about your task. If I had to guess, your line is probably not in that sleeve for its entire length. That sleeve is probably just a protective sleeve for where the pipe comes up through the slab. Suctioning the water with a shop vac should allow you to confirm that. Even if there is a continuous sleeve, the bend would probably make it nearly impossible to pull new copper through. The only possibility I would see would be to send an electricians fish tape through from one end to the other, try to pull pex in with that. Its all very iffy!

  3. #3

    Default Bummer

    OK, I think I'm seeing another picture.

    In this one the water is flowing under my slab, washing out the fill, drawing termites to it and a little of the water is even following the pipe up (this is what I saw).

    OH MAN - that changes everything. Thanks for your candor, I guess its time to get busy.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Being in Texas, I thought termites were a given! Especially with the moisture. Slab leaks are a big pain. Most people give up and find a way to run them above the slab, since if you find one leak, there are probably others, either now, or shortly after.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5

    Default Thanks!

    Thanks Y'all,

    As soon as I recover from my depression, I guess I've got stuff to do.

  6. #6
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default leak

    The good thing about your situation, is that when water comes up out of the "sleeve" that usually indicates that the leak is in the sleeve, or very close to it.

  7. #7


    Hey - THANKS!

    At least there's one positive. I'm thinking that when I do this I should just go ahead and do the hot line at the same time.


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