Asked on Mar 15, 2020

What could be causing a wet floor, if a plumber finds no leaks?

by Brian

wet floor under sink dry iu and run water no leak? no smell all is clean. run water both tubs, garbage disposal, use sprayer everything underneath stays dry. Go away for a few hours come back wet under sink nothing is loose nothing is wet? Had a plumber here no leaks was his call??? gets wet evyday? what could it be?

  21 answers
  • Zard Pocleeb Zard Pocleeb on Mar 15, 2020

    On a day when you’ll be home dry everything under the sink to include drain pipes, the area where the sink basket attaches to the sink, valves, etc. Place a double layer of paper towels under everything and leave it alone. Check the paper towels every hour or so for dampness, which will show up prominently. When you see a wet spot look straight up and you should find your leak. You can also consider hiring another plumber to check it.

    comment photo
  • Ken Erickson Ken Erickson on Mar 15, 2020

    Paper towels on the floor and elsewhere (pipe connections, etc.) is how I look for leaks.

  • Redcatcec Redcatcec on Mar 15, 2020

    Good suggestion from Zard, another place to look is under the faucets under the sink, the connection there maybe loose. Or maybe the hoses are about to burst from the pipe to the faucet. Best to you...let us know what you find out.

    • Brian Brian on Mar 15, 2020

      okay I pulled out the faucet line its a moen all the way out and re tightened and will keep an eye on it, thanks BD

  • Nan W. Nan W. on Mar 15, 2020

    Hi! I had that problem (with clean water)... it was the shut off valve!

    Maybe this will help:

  • K. Rupp K. Rupp on Mar 15, 2020

    We had an issue once where it was the connection (or valve) of the dishwasher which was leaking under our sink and then leaking under the floor cracking all kitchen tile grout. It got to the point there was water in our basement under that area. It was a slow leak which was hard to detect. May want to check that as well. Check any appliance that uses the water line.

    • See 2 previous
    • K. Rupp K. Rupp on Mar 16, 2020

      Ok this is what he told me because I couldn't remember since it was a few years ago:

      'That leak was do to a cracked coupling (or inlet) under the dishwasher where the water line (the pipe that carries water to the machine) connects. Yes it did leak even when not in use because the water to the machine is under constant pressure. The control valve is part of the machine so it can control its own water supply.'

      I hope this helps and maybe this makes more sense to you than it does to me. lol. Good luck!!!!

  • Mogie Mogie on Mar 15, 2020

    We had a problem under our kitchen sink. Turned out our water filter had sprung a leak. Easy fix just replaced it.

  • Johnavallance82 Johnavallance82 on Mar 15, 2020

    Hi there,

    Could be appliance cable leak(Crack) in connecting cable when in use (or from under pressure) when not in use, or coming up from under floor! Does the water smell or coloured in some way?........

    • Brian Brian on Mar 15, 2020

      the water does not smell? I pulled the moen faucet all the way up and tightened the crap out of it? so will keep an eye on the floor, thanks BD

  • Tom Stuart Tom Stuart on Mar 15, 2020

    Ken Erickson has the proper detection method. Make sure the area is dry, put down the paper towels, then check in 5 minutes. Do not go away for a few hours as you said but check it every 5 minutes. Set a timer and keep checking every 5 minutes until the edge of the paper towel is wet. Once it is wet start looking in that direction.

    Please add the results to this question and someone will have another suggestion.

    • See 1 previous
    • Tom Stuart Tom Stuart on Mar 16, 2020

      The leak will either come from above if the wet spot is surrounded by dry towel. If the towel is wet along the edge look in that direction. If it is wet all over you need to dry it thoroughly and check it in shorter intervals. I recommended before that you check it at 5 minute intervals. It won’t do any good to check it when it is all wet.

      Also feel around all of the fittings around it. There should be a drop of water left around the leak which you can find with your finger tips.

  • Johnavallance82 Johnavallance82 on Mar 15, 2020

    Hello again Brian,

    Sounds as though one of the water supply pipes to an appliance has a split in it. Wrap a cloth or tissue around each pipe you have underneath the area. The check it very often, and that should tell you where the problem is! If no wet cloth or paper, then it must be coming up from the floor! Good luck!

  • We had a problem with the seal under our drain that went to our disposal wasn't sealing properly. Once it was removed and new plumbers putty put down, we haven't had any issues with leaks since.

  • Kathy Gunter Law Kathy Gunter Law on Mar 16, 2020

    Check your cut off valves to make sure they are not leaking. We just replaced one for the same exact situation.

  • J Brown J Brown on Mar 16, 2020

    years ago had a similar problem, water but nothing leaking...

    Turned out it was a pinhole in the copper supply line in the wall.

  • Sandywilliam Sandywilliam on Mar 07, 2022

    One option would be to have another plumber come in for a bathroom inspection. Perhaps the one you called for the inspection is not sufficiently graded or has no experience with this particular problem. You can try to find the leak yourself. To do this, use dry paper towels. Wrap them around the suspected leak and wait. After a certain time, use the elimination method to find the leak. You will most likely need to replace the part to fix the problem. Doing any lining on the breakthrough will not have a long-term effect. If you want to learn more about plumbing or become a plumber yourself, I recommend going to There you can learn about how plumbers are educated, sign up for training, or find out any information in this area.

  • TobiasSlater TobiasSlater on Aug 22, 2023

    I remember when I had a similar issue a while back. We were convinced it was a leak too, but the plumber found nothing. After some research and a lot of trial and error, it turned out that the condensation from the pipes was causing the dampness. Crazy, right? So even though it seemed like a leak, it was actually just good ol' science doing its thing.

  • Rickuda Rickuda on Aug 22, 2023

    It may not be a plumbing problem per se, but a condensation problem. The cold water pipes running under the sink were causing moisture to condense on the pipes, and that moisture was dripping onto the floor. A plumber I know suggested using insulation or foam around the pipes to prevent temperature differences causing condensation. I can totally understand your frustration – plumbing mysteries can be so puzzling! I came across a helpful link that might shed some light on your situation They have some tips and tricks that could help you out. And maybe give this condensation idea a shot? I'm no expert, but sometimes thinking outside the box can lead to unexpected solutions.

  • Jason Most Jason Most on May 20, 2024

    Poor plumber work

  • Johnavallance82 Johnavallance82 on May 20, 2024

    No Dampcourse in the building! Call in a building Surveyor for evidence/ confirmation and remedy!

  • Melinda Melinda on May 21, 2024

    If a plumber can't find any leaks but your floor is still wet, other reasons could exist. It might be because of condensation, especially in humid places or near cold water pipes. Another reason could be a clogged drain, which can build up water on the floor. Sometimes, there could be problems with the water supply or sewer lines. Also, the plumber who checked wasn't very good at finding the problem. So, it might be a good idea to find a reliable one, like the Brisbane based plumber, who can figure out what's happening. They might have more experience or better tools to find the issue.

  • Kathy Gunter Law Kathy Gunter Law on May 22, 2024

    Drain leak?

  • Hi Brian! If it's not the pipes and it's not the foundation, the water might be coming in through the windows and doors of your home. Improperly sealed windows can leak on a rainy day, and the water can drain down the wall and into the floors and subfloors. If this happens, you need to start by sealing the windows with caulk. Hope this helps!

  • Kathy Gunter Law Kathy Gunter Law on May 29, 2024

    Drain pipes could be cracked