I wouldn’t put the rubber coupler right above the sump. Maybe bump it up to about 2 feet. That way if you can also use the pipe as a means of putting water in the sump to test it without breaking the seal if you ever want to. Also, since you’re going to have your nice hole saw out, cut and additional 4 and a half inch hole in the lid. Then cover that with a piece of lexan. That way you can keep an eye on the water level without having to take off the lid. One last thing. I highly suggest using duct tape to bridge the gap between the lid and the bucket first. Those lids rarely fit the buckets the way they’re supposed to. So if you put duct tape around the perimeter first, then cover it with polyurethane caulk, when (not if) you need to get in there again, you can just score the seal and the duct tape rips up kind of like a zipper. Much easier access rather than just filling that quarter inch gap with caulk. Good luck!

Hey George. Very valid question. We hear it all the time. Sure. Radon is roughly 7 times heavier than air. However, we are talking on such a small scale, that any slight breeze or natural air current will wisk it away. The main reason we want the vent stack to be up above the eve line more has to do with natural pressures of the structure. The lower on any building you go, the more air wants to get pulled in to said structure through what’s called the stack effect. Imagine any building as a piping system for radon. Where at the top, hot air is forcing itself out through the roof, and then to replace that air, the bottom is actively pulling air in from the surrounding soil. The whole point of a radon system (active of passive) is to try to give that air a path of least resistance so the radon (and moisture and other soil gases) is mitigated to a safe distance. That’s why they don’t call it radon removal, because we aren’t really removing it. We’re just giving it a nice path to dissipate outside. After that natural pressures prevent re-intrusion.

Prettiest option is always to put in the pipe during building so I applauded you know that. An ounce of prevention is worth a pound of cure.