Sealing a Bath Trap

[The Reverend Natural Light]

Howdy.

I'm about to close in the back side of a basement bath tub. Beneath this tub is what I'm told is called a bath trap or tub trap, a 1' by 1' square hole through the floor slab for the drain pipes. I'd like to seal this in to prevent termites and help an existing radon problem. Any ideas on how to do that?

I've thought about concrete. One bag would make quick work of it, but the day would come when I sorely regretted such a permanent solution. Another thought is spray foam but that probably wouldn't last very long. Perhaps a thick base of gravel with a thin layer of concrete over top. That might be removable enough for when the tub drain leaks years down the road. Any other ideas?

Thanks!

-rev

[oren]

Dude! I'd think more about solving "an existing radon problem"! If you half-ass patch the slab I surmise radon is still present.

Oren

"My doctor says I have a malformed public-duty gland and a natural deficiency in moral fiber, and that I am therefore excused from saving Universes."

[The Reverend Natural Light]

Please describe the difference between a half-ass and a full-ass patch of a slab and what effect each would have on the infiltration of radon gas from beneath the foundation.

Thanks.

-rev

[oren]

The "ass" method you choose is your's alone. I was stressing the radon issue, since you stated you have one. Of course radon will infiltrate other portions of the slab (not a expert). You didn't mention if you were correcting the radon problem.

Oren

"My doctor says I have a malformed public-duty gland and a natural deficiency in moral fiber, and that I am therefore excused from saving Universes."

[The Reverend Natural Light]

I'm attempting to reduce the radon concentration by sealing all paths through the floor and walls. Holes broken into the block for recessed electrical outlets have been patched, the sump hole covered, the wall to slab junction sealed with hydraulic cement, and all surfaces coated with multiple layers of concrete waterproofing. The last void in the foundation is the bath trap. Should these methods fail to reduce the radon concentration to an acceptable level, then I will fabricate a sub slab depresurization system.

The previous owner lived there for the last 40 of his 90 years, so the immediate health risks are low enough to justify an attempt at a low tech solution.

-rev