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toddmanqa 03-29-2012 08:48 PM

How to combine radon mitigation with drain tile/window wells?
I am in the process of soliciting bids for a contractor to take up my basement concrete slab, lower the grade a foot, and pour a new concrete floor.

My radon levels were 2.4 and 2.0 when I bought the house five years ago. Fairly low, but I thought they could be lower.

Therefore, I have requested a 10 mil vapor barrier be placed over 4" of gravel. All around the perimeter of the slab, an Enka drain mat will be installed 3" above the top of the slab, run down the side of the slab, and then under the slab and over the interior drain tile/aggregate. The drain tile will drain to a sealed sump pump. The Enka drain mat is installed to channel any water that may come in on the basement walls (I only have a little water coming in).

I plan to place sheet foam on the walls and floor (taped together), then foam the gap between where they meet at the floor/wall/enka drain junction, so that the Enka drain will be completely covered by sheet foam or spray foam.

I was also planning on running vertical drains to future external window wells.

I read that the interior drain tile system could be used for radon mitigation. I planned on pulling air from the drain tile and then to the roof with a radon fan. However, I'm now concerned that the system won't be effective at removing much radon since the air from the window wells will flow easier than the air under the slab.

Is there any way I can install water traps in the future window wells that will prevent air from being pulled from the window wells (and thus from under the slab instead)?


md2lgyk 03-30-2012 09:02 AM

Save your money. As someone who worked in the nuclear industry for over 30 years, I can categorically tell you that radon mitigation is a scam. Unless you live in your basement 24/7/365, there are many, many more things that will get you first.

toddmanqa 03-30-2012 01:04 PM

I think I've found a solution: free-floating guided lever traps.

Here is a link:

I plan to install these inside the basement.

So, the line from the window well will enter the basement horizontally, turn and go down, through a dandy cleanout, then hit the free-floating guided lever trap. When there is no water in the line, the trap will be closed, and the fan connected to the drainage tile won't be pulling fresh air from outside from the window wells. When there is water coming into the window well, the trap will open and the water will go to the drain tile and to the sump pit.

I considered a manual running trap or p-trap, but didn't want to place it ouside due to possible freezing weather, plus I didn't want to have to worry about the water in the trap evaporating or getting sucked in by the fan suction.

I will have to make sure that the fan pressure doesn't cause the value to NOT open when water is coming in.

md2lgyk 03-30-2012 06:48 PM

So you're intent on wasting your money? Well, I did try.

dougp23 03-30-2012 07:16 PM

Mine was 6.3 in my basement! 2.0 in the living room. They hand this out with the test results:

1. The EPA has advised homeowners to take action to reduce the radon in their home if the concentration in the lowest
LIVED-IN level exceeds 4.0 pci/L. This number was statistically generated based on a lifetime exposure of 18 hours
per day. W hen considering the risk YOU face from your reported radon concentration, remember to compare the
amount of time you spend in the level of your home where the measurement was made to the 18 hour per day factor.
You may wish to measure the radon in other levels of the home.

So it seems to say, you're not living in your basement, and even if you are, are you there 18 hours a day? But you have to go with you're comfortable with!

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