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Thread: Drain leak within concrete block wall

  1. #1
    DIY Junior Member
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    Default Drain leak within concrete block wall

    I have a concrete block house (on slab) dating from 1959. I think it just developed a leak somewhere in the kitchen sink waste line which runs within the block to a cast iron DWV stack (also within the block).

    If I just fill pots of water in the sink there's no water on the slab. If I run water through the sink and into the drain line I can't see any visible signs of leakage in anything under the sink. But water starts weeping at the base of the drywall behind the cabinets - water pools at the end of the cabinets.

    Needless to say, this is not making my holidays bright!

    I'm hoping it's just the elbow in the copper DWV line just inside the concrete block. If not, and I have to replace it farther back towards the vent stack, how much of the concrete can I break out and still have a solid wall? I figure anything under the window is fair game (as there is a header over the window), but there is another couple feet between the window and the vent stack.

    Thanks,
    Gary

  2. #2
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default

    You're going to have to pull the cabinets to make the repair anyway, I imagine, so I'd do that first and see if the leak can be located precisely. You may find that the waste lines have been run in a rabbet on the inside of the block wall, and no further demolition of the wall is required to find and repair the leak. The drywall behind the cabinets is probably toast, though, but the key phrase is "behind the cabinets" -- i.e., easy to demolish, not important to make pretty when you finish up. And, if you work for Gainesville's largest employer, you're probably free until Jan 2, so you've got lots of time to have at it!

  3. #3
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    Default leak found - now what?

    Well, it wasn't the elbow, darn it. Looks like most of the interiors of one row of blocks were knocked out in order to accommodate the copper drain line, and when it they mortared in the blocks the concrete wrapped most of the way around the copper waste pipe in at least one place. Thatís where itís leaking from. It lasted 50 years, but if they had wrapped the pipe with tar paper or something similar it probably would have lasted another 50.

    Any opinions as to whether I should couple it (which would be buried in the wall), replace it (requiring more block to be open to get a long enough length of PVC in), or do something else?

    And yes, I do work for Gainesvilleís largest employer, but the kids want to bake Christmas cookies - I have to get the sink working again!

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    Forum Admin, Expert Plumber Terry's Avatar
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    If it's a waste line in copper, you can use banded couplings and cut in some new pipe.
    They make copper to plastic couplings.

  5. #5
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    A banded coupling would indeed be the easiest fix. I would be concerned that this leak might be the first of many, though, so would be inclined to replace the entire length of pipe while you've got the wall open. You could just repair the leak temporarily (duct tape comes to mind) to get the cookies done, and effect a permanent fix as time permits.

    Mike

    (Recently retired from GLE.)

  6. #6
    General Contractor Carpenter toolaholic's Avatar
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    Thumbs up Another Idea

    do a search on Ridgid Micro snake $199 Tool up. You will be able to drill a 1"
    hole through cabinet back with a wood speed bit. Then roto hammer into block
    face. You'll be able to see any leaks ,while running the sink. I own one and also have one 3' extension, total 6'. Don't use it often, but when I do, it's a life saver.
    All this said You'll probably have to open up some wall. Show this tool to any electrician or plumber,You'll sell it! It's lighted in color,You won't believe the clear picture

  7. #7
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    Default Mission Accomplished - cookies baked!

    Thanks everyone! It's been busy around here catching up from the time I spent on fixing the leak, but I did get everything replaced and put back together in time for cookies. I hope you all have a Merry Christmas and a Happy New Year! (And I finally got to use that air chisel attachment in my DeVilbiss air tool kit - I highly recomend it for opening up the block )

    By the way, a friend of mine who was out of town told me yesterday that I could have taken out as much as 3 blocks in one area as long as I just took out one side of the block. I only needed about one and a half to get the pipe in.

    Gary

  8. #8
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default

    What, no pictures?

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    Licensed Grump GrumpyPlumber's Avatar
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    Default

    Quote Originally Posted by Mikey View Post
    A banded coupling would indeed be the easiest fix. I would be concerned that this leak might be the first of many, though, so would be inclined to replace the entire length of pipe while you've got the wall open. You could just repair the leak temporarily (duct tape comes to mind) to get the cookies done, and effect a permanent fix as time permits.

    Mike

    (Recently retired from GLE.)
    Thats the right call, opening concrete is a pain in da keyster.
    If there's one leak, there's more to come.
    Do it right and avoid having to reopen the same concrete in the not so distant future.
    "The biggest regrets we have in life are the chances we never took."

  10. #10
    Master Plumber master plumber mark's Avatar
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    Talking how about a pic

    I would like to see the mess myself..

    sometimes it easier to start at the stack and
    simply leave that dirty arm in the block wall
    alone....

    re-running the pvc line through the cabinets
    from the main verticle stack perhaps could be
    an easier option if the verticle stack is still good...

  11. #11
    DIY Junior Member mc2's Avatar
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    Default

    I've had a similar problem with my home which was built in 1961 in Hawaii. I too cut the wall out, replaced the original pipe that had been bent upwards during the initial construction. It lasted 50 years in that shape with crud sitting in it! Amazing! We renovated the home about 5 years ago, covering the exterior CMU walls with plywood and baton to get a plantation look.
    Since the main sewer line was located under the garage slab, we decided to reroute the drain line and have it go around the driveway to avoid any big cuts in the concrete and have it reconnect near the front of the driveway. We still had to cut a part of the sidewalk and while doing so, found where the previous plumber had buried the gas line for the stove. About 2 inches below the surface of the sidewalk . So now, we've got to reroute the gas line as well. Only place for us to put that line was inside the wall as well.
    I didn't want remove the cabinets, so I decided to cut the CMU from the outside which meant removing the exterior ply. So, now that I have the wall open and the pipes have been replaced, rerouted and tucked back into the wall,( please note that the gas line is now in the wall as well), I wanted to make sure that the wall is structuraly sound. I shore up some forms against the wall, cut a hole above the pipes, and fill with concrete (quickcrete).I made sure that there was a connection between the blocks so as to prevent any possible sagging. My worry is that now, I have gas and drain embedded in concrete in the wall. Hopefully, this project will last another 50 years. Any thoughts on my solution to this problem?

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