Help troubleshoot my mystery wet spot

This is a real headscratcher.

Around a month or so ago, we discovered a wet spot in our hallway. The wetness involved a carpeted (wall to wall) area about 2’ x 2’. It was sodden. The wetness had no odor, but we have three dogs, so the assumption was that one of them had urinated.

I used towels, then our carpet scrubber to extract the liquid and then a fan to dry the area. The dogs were kept away from the spot. A week or so later, the exact same spot was soaked again. I again dried the area, and again it is wet.

I measured the distance of the spot from the rear and side of the house, then went down to the basement and found the exact spot. I moved the suspended ceiling tile and looked. No water lines, no moisture. Hmmmm.

My gf suggested a leaky roof that allowed water to run down from the attic inside a wall adjacent to the wet spot. I went up into the attic and all was dry.

The spot is several feet from an outside wall where water could conceivably get in, but there is no evidence of moisture between the wall and the wet area of the hallway.

Ideas? Suggestions? Who can I call who could investigate this further?

Does it happen to in any way resemble Jesus or Mary, even in a vague, abstract way? Because if it does, you may be sitting on a gold mine!


How old is your house? Our 1920 house has some weird wet spots; one was solved by identifying a radiator pipe that was leaking under the hardwood floor. The others are just . . . mysterious. I pretend not to see them, as nothing has yet collapsed.

The house is 30 years old. There is hot water baseboard heat, but none of the lines go anywhere near the wet spot.

You’re absolutely sure the dogs have not been able to get to that spot?

100% certain.

Additionally, the liquid is odor free. Plus our dogs have never urinated in the house. Because it seemed the most likely explanation, we gated off the area.

It’s like someone is periodically breaking into our home and dumping a bucket of water in the same place.

Have you tried lifting the carpet? I’m assuming you didn’t mention the upstairs bathroom because there isn’t an upstairs… (?)

There is a basement, one floor, and attic. I have a blueprint of the house and the wet spot is totally isolated.

There is a bathroom in the basement and one right above the basement bathroom. The hall is near the upstairs bathroom, but no water or waste lines go near the wet spot.:frowning:

New wall to wall carpeting was installed two years ago. I’m not looking forward to lifting the carpet.

Has it been raining where you live?

A couple of years ago when cleaning I noticed the window in our upstairs bathroom was shattered, but still in place. No idea what caused the breakage, but we had it replaced. This was just a window, no slider.

Last year, which was near record with winter storms hitting that side of the house weekly, we had a wet spot that would not dry in the carpet. We thought it was from the bathtub, but it was totally dry around the tub. Eventually, the carpet started to stink, so we ripped it up and dried out the floor and laid down some temporary sticky tiles (we are planning a remodel anyway). A few days later, another storm, and a wet spot on the tiles in the middle of the floor (several feet from the outside wall). I took the time to follow the wetness to it’s source, and found rain water dripping from the aforementioned fixed window area, inside the wall behind the tub (tub has access), and then spreading under the tiles. Eventually a spot appeared on the ceiling below. Ugh!

Got out there and double-sealed the entire window frame with silicon - every little opening and hairline crack. Seemed to have stopped the entrance of the rain water, but we still keep towels over there during storms.

Anyway, the point being, if it has been raining a lot, rain water may have found an entrance somewhere, and the water found it’s way to your hallway. As also mentioned, there could be a small leak in the roof and water is just following the walls. If you can tie the appearance of the wet spot to the weather, at least you can rule-out a leaky pipe, and focus on the exterior of the house.

I’ll take “Thread Titles You’re Afraid To Click Open” for $200, Alex.

So you’re saying there should not be any water lines in the walls on either side of the wet spot in the hall, not bathroom, not kitchen… hmmmm… Okay, is there an electrical fixture directly above the wet spot?

Yes, there is a light fixture right above the spot. :confused:


Some rain, but no windows. There is a skylight in the roof over the bathroom which is adjacent to the hallway with the wet spot, but I’ve been up in the attic and everything is dry.

That’s not where you put your kayaks after you use them, is it?

When was the last time you got really drunk before going to bed, and then got up because you had to pee? Hint: You didn’t make it to the bathroom.

I know you said you were up in the attic and it looked dry, but I assume there’s insulation in the ceiling joists and I don’t know if you actually lifted the insulation above the light fixture. Just for shits and giggles, see if the inside of the light fixture in contact with the ceiling is damp. Prolly best to shut off the relevant fuse before you touch it.

Another thing to try, if you’re out of ideas, is to lay down a plastic tarp and put a large piece of cardboard over the wet spot. You’ll know pretty soon if the water is coming from directly above (light fixture?), or trickling down under the carpet from somewhere laterally (walls?) and is simply pooling in the low spot of the hall.

I think you might be on to something.

But no, I suspect the light fixture.

My son’s house is about 100 years old and they were getting mystery leaks in a bedroom–turned out it was dripping down following electrical lines and dripping out the light fixture so it’s not a far fetched idea.

I endorse putting down plastic to see if it’s coming from above or below.