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Thread: Slab leak... need help!!

  1. #1

    Default Slab leak... need help!!

    Need help with this one! But I have too much pride to hire someone for the job. I also am a handyman by trade, so I am comfortable with this repair.. with a little direction.

    South florida home. CBS construction. Found a few ounces of water in my garage. Traced the water back to the wall behind my washer. Opened the wall. Found the water coming from a copper pipe that comes out of the slab floor. Its 1/2" flex copper thats encased in black plastic tubing. I cut away the tubing to the slab to make sure the leak wasnt coming from above.

    Clearly the leak is coming from the slab. But rather than opening up the slab with my jackhammer.. and really pissing off my wife... i figured I would try to reroute the line.

    Follow me for a second. Here is the layout from top to bottom. 1/2" copper coming out of the ground. T's off in two places to feed a sink and also a washer. THEN IT TURNS INTO 3/4" COPPER and continues UP into my attic.

    So correct me if I am wrong... but I can cap it before the ground... figure out what room no longer has water... then drop in a pipe from the attic?

    Thats the easiest solution, right????? I DO own a jackhammer.. but what scares me is the fact that with that plastic tubing.. there is no way to say for sure how far away the leak is.... could be 50 feet from where its coming out. Would follow gravity.....


  2. #2
    Plumbing Contractor C NUMB's Avatar
    Join Date
    Jan 2009
    NPR, FL


    Your on the right track. Maybe you will get lucky and the line going into the slab supplies a hose bib if the leak is on the cold line.
    I'd Rather Be FISHIN'

  3. #3

    Thumbs down Slab leak

    Thanks for your reply. I too would rather be fishing! Nice boat.

    Whats throwing me off is the following. There are TWO 3/4 copper pipes going up into the attic, and two 1/2 flex copper going into the slap. If it were just the cold going to the slab, your right it would likely be the hose bib. I need to figure out how my house is plumbed. If its all 1/2 flex coper under the slab or if its mostly in the attic and the flex copper was run to just one room. There is an island in the kitchen, but would have been 3 other rooms that would have been closer to the island to supply it. Will be climbing into the attic now. And next, will splice the tube going into the slab, cap it, and see what doesnt have hot water anymore. South florida, CBS house. 10 yrs old. If anyone else is reading.

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default tubing

    Normally, it is not going to be a ROOM. It should be a single fixture, probably a shower or tub, but if they ran most piping in the attic, it is assumed that ANYTHING that is under the slab is going to something that THEY could not connect from overhead.

  5. #5


    mrooge - It seems that you are on the right track - cutting and capping the feed side of the 1/2 line "to determine what it serves". It will also serve to prove that you have the right line isolated and that there are no further leaks. Once, that is accomplished - You may very well tap into a line in the attic in order to re-route and re-establish water to the fixture(s) previously served by abandoned 1/2 line. Note: A good way to immediately know whether you have the right line (as it relates to the leak) is that the line won't hold water. e.g. you cut into the line and visiually see the water level drops. If it doesn't you may not have he right line (line containing leak)

    The one thing I'm scratching my head on is "There are TWO 3/4 copper pipes going up into the attic, and two 1/2 flex copper going into the slap."

    It is not common for two 3/4 lines of the same variety (e.g. hot or cold ) to be going up into the attic by which you explained. Either one is cold and the other is hot. Had you said: There are two 3/4 lines going into the slab - I would see the reasoning 1 being the supply to that fixture "washer" and the other continuing back under to supply next fixture in line. So, I see it important for you to properly identify both lines. Are both of the 3/4 lines attached to the manifold in question ?

  6. #6

    Default Slab leak

    Alright... I opend the wall. I found some mildew behind the baseboard. So I ripped out the baseboard and all the drywall within 5 feet of the leak. I know the configuration of the pipes now, also where the water is coming out of the slab. There is a hot and cold water line, made of 1/2 flexible copper tubing, and contained in a sheath of black plastic tubing. The leak is definately below ground. The water was coming out of the tubing, which came a foot out of the ground. I cut it back to the slab but the leak is below ground.

    I dont want to replumb from above. Those 3/4 pipes were just to help with water hammer. All my pipes are below ground.

    What throws me off is this... with that plastic tube the leak could be 50 feet away, right?? The water leaks out of the copper in one place and then follows the plastic tube to the lowest point or the point of least resistance.

    I thought of drilling some 1/4 inch holes in the slab to pinpoint the pipe leak...
    but honestly dont know what that will accomplish since the water is coming out of the tube. I have a jackhammer... and think I go at it tomarrow. I just dont have any reasonable expectation finding the leak where i dig... i get the feeling it could be very far away....

  7. #7
    DIY Senior Member TedL's Avatar
    Join Date
    Sep 2006
    NY Capital District


    There are leak detection tools that could locate it, but after you find it, the repair requires special handling. No standard solder joint underground. The type K (soft temper, what you're calling flex) is used under slabs because it comes in long lengths.

  8. #8
    Join Date
    Aug 2007
    Houston, Texas, United States
    Blog Entries

    Exclamation Slab leak ! ! !

    I am going to give you the same advice i posted to you on the other forum

    call a professional to at least do the locate for you !

    Then you can decide which is best to repair the existing pipe or to reroute
    around the bad pipe

    please call www.floridaleak.com
    or any other plumber that do'es leak locating in your area they can give you the best advice you can still do the repairs
    your self or decide on this job if you want to pay them and learn by watching how they do the work ! ! !

    MACPLUMB 777



    Trojan Worldwide Web Site


  9. #9
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default leak

    The tubes are usually only on the copper where it penetrates the concrete floor, so the leak is probably in or just below the concrete. It would also normally be the hot water pipe.

  10. #10

    Default slab leak

    Thanks for everyones advice. I will be cracking open my slab today. I totally appreciate your advice. I know its BEST to call a professional. But I live in a region where calling a professional means being ripped off. My friend had a professional charge him $500 to fix a single polybutylene fitting. I can give you many more examples. And as a handyman by trade, I have all the tools to do this repair. But am just not 100% familiar because I havent dont it before. Im sure I will do fine. Believe me, I have had my share of screw ups. I just dont see this as one of them.

    MY next question... is how to make the repair to the flex copper after I find the leak. I know how to solder very well. I also know all about shark bite connections. But someone already replied that it wasnt a standard solder joint. I dont have a oxy-acetyline rig. Should I call in a favor from a friend... or should I solder it and be done with it.

    And, what special precautions should I take when repouring that concrete after the repair? I know I need to replace that black tubing. But should I replace it with something much larger to keep the concrete as far as possible off of the copper??


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