I've striped my basement floating floor, as I want to have a epoxy/polyurea flooring installed. I've found this hole, with a plastic frame, under the floating floor. It was covered with some transparent tape and there was some kind of sealant inside the tape around the hole.

The new flooring would cover it. So, I wonder:

  • what is this hole ?
  • what's the purpose ?
  • why was it taped and sealed ?
  • anything special I must do/not do as the new flooring cover it ?

Extra information: I believe there's some sort of pressure differential, as I was feeling a very slight breeze from it (I think) with the tape removed. It was raining outside today and I believe I heard a very faint gargling noise from it (might have been coming from outside, though).

House is in Quebec, Canada, build around 2005.

Lastly, spouse is very concerned about radon gas and anything that might be a way for radon to get in or accumulate is extra concern.

Thanks !

The coin, for sizing, is a canadian 2$, barely larger than a quarter.

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1 Answer 1


It's a floor drain. It was covered in an attempt to keep sewer gas from coming out of it once the trap dries up.

If you're going to cover it, it should be an airtight seal. But blocking off the floor drain in your basement is up to you. Even a small flood could become a real problem.

If you find a way to leave it functional, add some water to it every once in a while to fill the trap back up.

  • 1
    There's a drain for the central AC nearby, a second drain for the water heater, and the garage (next room) has a large drain too. I can afford to seal this one.
    – Jeffrey
    Oct 8, 2017 at 21:24

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