Apologies if this has been asked here before, my first time on the site coming from Reddit.

I just built a new house and know that the radon levels are high due to neighbors doing testing / the area we live in, so I'm going to install radon mitigation. The house already has a radon vent line from the slab up to the roof with electrical in the attic to install the fan - so that part is easy.

However, I also need to seal the sump pump as it currently just has an open cover on it. My question is do I need to vent the sump pit somewhere, and if so, do I vent it directly into the radon stack (they are very close to each other) or do I need to vent it to a plumbing vent line? I've seen mixed reviews on if it needs vented at all, but since it is also a location for radon to enter the house maybe it makes sense to have the radon fan draw air from this area as well.

Any guidance is much appreciated!

  • Do some actual testing and/or get a monitoring device (affordable nowadays, as opposed to unthinkable in a prior era) for quicker feedback, rather than merely going by the neighbors' tests.
    – Ecnerwal
    Commented Sep 20, 2023 at 12:42
  • See also: diy.stackexchange.com/a/257279/18078
    – Ecnerwal
    Commented Sep 20, 2023 at 15:11

1 Answer 1


It's normal and customary to connect the sump to the radon vent.

The negative pressure on the radon vent is negligible to the sump pump operation, (has no effect on it pumping water out) and the sump piping (and/or connection to drainage rock) serves as access to pull more radon out from under the floor.

Pay attention to the power use of your fan choice - that will be running 8,760 hours a year (8,784 leap years) until it dies and is replaced by the next one. You'll pay many times over for an inefficient fan.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.