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There is a damp line being formed behind the toilet commode, as seen in the picture. Any suggestions on where the problem lies would be appreciated.

enter image description here

Edit:

I've added pictures of what it looks like with the lid off (the lid is usually left on) . I don't particularly see any signs of condensation on the inside. Also attached is a picture of the wall right behind the commode so you can see how far down the wall the damp line runs (annotated the level with a red arrow)

The toilet is on the 1st floor of a 2 story home. However, on the 2nd floor, there are no drain pipes right above this toilet that I can think of (there is a game room right above).

enter image description here enter image description here

cd234
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4 Answers4

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The mark could be from condensation on the cold water pipe. As the pipe warms, when not in use, condensation stops. If that is the cause, there likely would be condensation on the toilet tank.

Some fixes for condensation:

  • Easy: Reduce humidity in the room. If there's a shower, there should be a vent fan.
  • Harder: Open the wall and insulate the supply pipe.
  • Harder and less efficient: Use a mixing valve to warm the cold water supply line. One reason to do so in very cold climates is to help prevent pipes from freezing.
DrMoishe Pippik
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Temporarily tape a piece of paper so it hangs loosely between cistern and wall. A sheet of newspaper would be fine.

Intention is to figure out if the damp is coming from inside the wall, or from the room. Maybe there's a spray of water from a pipe when you flush - if so the paper should catch it and show this.

If the paper stays dry then the source is inside the wall, and you're up for some exploratory wall excavation and some plaster work afterward.

Do you have access to a bore-scope camera? If not, it might be worth buying a cheap chinese one, the sort that connects to a cellphone. This will allow you to drill a small access hole in the wall which is easier to patch than a head-sized hole.

My suspicion is that something's leaking or sweatting inside the wall.

On the other hand you have a Bidet which contain pressurising pumps and pipes. So a tiny crack in a pressurised line could result in a fine mist that sprays, and drips down the wall. Need to confirm or eliminate if the source is in the wall or not.

Criggie
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I would not think condensation would seep through a 3/4" thick drywall and then even if it did, dry up so quickly.

I would guess you have a very small leak that sprays a fine mist when you use the toilet. I would flush the toilet and run your hand all around and feel for when your hand gets sprayed. Shine a flashlight as well as it will pick up a mist spray quite well

SpecialK
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Drill a 4 or 5" hole using a Hole saw ( being care full as you drill) . Either side of top water stain. put your hand in to feel for any water lines / drain lines etc. You may also be able to shine a light . Has to be a source of leak in the area Other option is to cut a square hole , possibly 5"x5" immediately where the water stain begin on top.

Kishore Patel
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