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Myserious water leak

user-55757 | Posted in General Discussion on January 10, 2006 05:54am

Hi All,

I have a mysterious water leak in the drain pipe coming from my kitchen sink. The leak is intermittant and seems to occur only when the dishwasher empties. I’m thinking that maybe the super-hot water from the dishwasher is causing a crack in the plastic to expand. I’ve dumped a five gallon bucket of hot tap water down the sink and it doesn’t leak so it’s not volume-related.

Anyway, the drain pipe runs horizontally along a wall, then tee’s into a vertical stack/pipe and then drops down into the basment. The water is dripping off the vertical section of the pipe when it makes a bend to join the main drain. From the basement, I can see water stains on the plywood subfloor around the pipe but having opened the wall in the kitchen, there is only a small wet spot on the bottom plate. There is no sign that the water is leaking somewhere above the bottom plate and dripping down and I haven’t been able to get it to leak while having access to pipe (it’s behind my fridge). It looks like the leak is in the section of pipe as it passes through the bottom plate. I’m thinking of cutting out the bottom plate and plywood subfloor around the pipe to get a good look at it, however the wall is load-bearing. Do you think the structural integrity of the wall will be compromised if I cut out a section of the bottom plate between studs?

Any suggestions to deal with this? Thanks!

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Replies

  1. JTC1 | Jan 10, 2006 06:09pm | #1

    Find the leak before you cut any more out.

    It sound like you have access to the pipe above and below the bottom plate.

    Suggest you dry the pipe thoroughly and then run the dishwasher through a cycle.  feel the pipe as the water passes through it - look at your fingers - gloss of water on fingers = leak somewhere above.

    If you already know for sure that the leak is in the run of pipe which passes through the bottom plate then just cut that section out and replace it using a pair of couplings.

    Thought - where does the pipe go above the point where the dishwasher / sink drain ties in? Is it a vent stack? or a wet vent from something upstairs?  If a vent or wet vent your problem may be at the top of the fitting where the dishwasher / drain ties in - rain water does travel down the vents.  Could be the pipe only leaks when it rains?

    Jim

    Never underestimate the value of a sharp pencil or good light. 

    1. User avater
      BillHartmann | Jan 10, 2006 07:08pm | #2

      And the pipe not even be leaking, it might be flashing around the vent throug the roof.My folks old house they would get a wet spot on the kitchen ceiling after a very hard rain. Only happen about once every other year or so.Never found the leak. Even happend after the roof was replaced.Happen to be in the attic one day and turned just the right way and saw glint of daylight.Turns out that there was a very small pinhole in the flashing for the vent stack. Only very hard rain from a specific direction would force water through it, then it ran down the rafter aways and drop down. So the wet spot was far from the source.

      1. user-55757 | Jan 10, 2006 07:28pm | #3

        Thanks for the advice guys. I'm pretty sure it's not leaking from the around where the vent goes through the roof since there is no connection between rain/snowmelt and the leak (i.e. bucketing rain out but no leaking). I only saw the leak once and this was when the dishwasher was emptying, all other times, I've just seen the water on my workbench in the basement after the fact. I've tried running the dishwasher a couple of times but so far haven't got it to leak before my very eyes. It's very frustrating!

        1. r | Jan 11, 2006 12:39am | #4

          Maybe wrap all the pipe you can reach with paper towels and scotch tape them in place?  A wet spot later will be obvious, or even if it leaks and evaporates before you see it, the paper towel in that area will look and feel different after having been wet.

          1. MSA1 | Jan 11, 2006 03:50am | #5

            I second that. Everytime I install a new sink, I put cardboard under the drain. If it leaks you will see it on the cardboard, even if it dries before you get to check it.

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