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Thread: Leak in the supply line to the bathroom

  1. #1

    Post Leak in the supply line to the bathroom

    We just moved into our first home. The house is 11 years old. The house is on two levels. There is no crawl space. On the ground level there is a half bathroom (i.e. toilet). I have noticed that the floor of the bathroom gets slightly wet from time to time. I cannot see any leaks or drips from the toilet bowl or any pipes. We kept a dry paper towel on the floor in the night. The next morning the paper towel is wet. I don't know from where the water is oozing onto the floor. Is it possible that the water supply line is below the floor (or behind the side wall near the floor level) and a leak there is causing the water to ooze onto the floor? How will a professional investigate the cause of the leak? Will they have to rip open the floor or side wall? I am scared. It is just one month since we moved into what we thought was a picture perfect home, and we are already starting to see problems. Please help.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    It could be condensation dripping down. One of the biggest reasons for that is a leaky flapper valve which causes the toilet to run to refill the tank periodically, adding cold water which can cause things to sweat. Simple fix, replace the flapper valve, a 1-minute task.

    Does the toilet rock at all? It MUST be sitting firmly on the floor. If it rocks, it needs to be reset with a new wax ring and shims. The wax is not resilient...once it gets squeezed out, it won't flow back, so the seal could be broken.

    If the toilet is a two piece, and the tank can rock on the bowl, the gaskets might be unable to maintain the seal...it might just need to be tightened up a little.

    Those are the to most common things, and well within the maintenance level of a semi-handy person.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3


    Let's get this straight: You do not see or feel any moisture dripping down from the front or back of the toilet tank, the bowl, or the toilet shutoff valve and supply line?

    If that's true, then water may be seeping out from a bad wax seal at the base of the toilet.

    Wrap your paper towel completely around the base of the toilet and flush it a couple of times. If the towel gets wet, then you need to pull and re-mount the toilet.

    Also, have you checked for leaks in your lavatory faucet and drain? Water could be leaking from under that cabinet and flowing to other parts of the bath floor.
    Last edited by Verdeboy; 04-22-2008 at 10:02 AM.

  4. #4


    Thanks for your responses. Just wanted to reply to your points

    I do not see or feel any moisture dripping down from the front or back of the toilet tank, the bowl, or the toilet shutoff valve and supply line. But I have only done a cursory examination. I will check more thoroughly.

    The part of the floor that gets wet is near the wall and closer to base of the toilet. The base itself appears to be dry. The floor around the faucet and drain is dry.

    I will try wrapping the paper towel completely around the base of the toilet and see what happens. Thanks for the suggestion.

    Where does condensation occur? Does it drip down from the wall? The wall of the bathroom is all dry.

    The toilet does not rock. It appears to be firm.

  5. #5


    JAD is referring to condensation from the tank. This is a function of the humidity in the air.

  6. #6


    I asked the folks at home to wrap a paper towel completely around the base of the toilet. They reported that the towel on the floor at the back of the toilet was wet. Does this indicate something?

  7. #7


    It does. But only you can determine where the water is coming from.

    You need to use a flashlight and to look and feel for any moisture behind or under the toilet tank and behind the toilet bowl.

    One experiment you can do is dry the area behind the toilet and to NOT USE that toilet for a few days. If it stays dry, then a qualified person needs to pull the toilet and remount it using a fresh wax ring.

    If the paper towel gets wet again without having used the toilet, then you either have a leak or it's just condensation build-up.
    Last edited by Verdeboy; 04-24-2008 at 11:33 AM.


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