Radon venting in 1/2″ crushed rock?
dsmcn
| Posted in GBA Pro Help on
I have about 9″ of 1/2″ crushed stone as a base for the slab (2″ of foam will go between stone and slab). I searched for clean, no fines, and the best I was able to get is mediocre clean.
Will installing 4″ perforated PVC pipe in this material still work as a radon vent?
Would the efficacy be improved if I backfilled the 8″ deep x 8″ wide trench for the pipe with 3/4″ rock?
How long should the pipe be?
Thanks.
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Replies
David,
Q. "I have about 9 inches of 1/2-inch crushed stone as a base for the slab ... I searched for clean, no fines, and the best I was able to get is mediocre clean. Will installing 4 inch perforated PVC pipe in this material still work as a radon vent?"
A. I don't really know. I have never heard of a grade of stone called "mediocre clean." What does it look like?
My guess is that it is still better than soil.
Q. "Would the efficacy be improved if I backfilled the 8 inch deep x 8 inch wide trench for the pipe with 3/4 inch rock?"
A. Yes -- but where are you going to get clean 3/4-inch crushed stone? I thought that all you could get is "mediocre clean" 1/2-inch stone.
Q. "How long should the pipe be?"
A. This question is discussed in a comment (Comment #21) posted on my article, All About Radon.
In that comment, I wrote, "As far as I know, the length of the horizontal perforated pipe used for a passive radon system is not specified by any standard or regulation. Common sense should prevail. If the layer of crushed stone is clean and continuous, gases should move fairly readily through the crushed stone layer, even if the perforated pipe does not extend to every corner of the home's footprint. Remember, though, that perforated pipe is cheap."
David,
The holes on standard perorated pipe will either admit the 1/2" stone or block the air flow. The solution is to either use larger stone, like the drain rock you use on exterior perimeter drains, or make your own perforated pipe with a smaller drill bit. This is a surprisingly quick task I do all the time.
Malcolm, what if I just wrap the pipe with geotextile fabric?
David,
That may well work. I just don't know how much the fabric will impede air flow, especially over time.
Or you could buy a socked drain tile... do it every day! http://www.homedepot.com/p/4-in-x-100-ft-Corex-Drain-Pipe-Perforated-with-Sock-04730100BS/100129255