Radon Mitigation: ideal location of intake


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Old 03-02-18, 08:30 AM
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Radon Mitigation: ideal location of intake

Most, if not all of the illustrations I have seen regarding slab depressurization depict the intake near an outside wall.

Would the system not theoretically be more effective to locate the suction at or near the center of the slab rather than off to one side?
 
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Old 03-02-18, 08:40 AM
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The Radon gas originates below ground (usually) or in the aquifer, so you'd want to evacuate it from below the slab before it gets into the living quarters. What I've seen here (as a Real Estate Broker), is an opening at the far end allowing outside air to enter and replace the air below the entire length of the slab and to then be pumped back outdoors at the far opposite end.,
 
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Old 03-04-18, 02:22 PM
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makes no difference to the radon,,, what vt's seen is the least expensive tactic
 
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Old 03-04-18, 03:56 PM
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An important part of the mitigation is "what is under the slab". Prepared before the concrete was poured would be a network of pipes plus several inches of gravel so any gas from anywhere under there could be extracted from almost any location. Since it requires an exhaust vent I usually see them on the outside walls.

Do you know if there are any pipes under the slab or at least a good layer of gravel with maybe a layer of plastic between it ant the concrete.

What did you get for test numbers?

Bud
 
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Old 03-05-18, 09:14 AM
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I failed mention that this is an existing home

This home in SE MN was built in 1986; no perforated pipe exists under the slab.

It has a wood foundation and is built on soil that is well drained with a high gravel content. Perforated pipe perimeter drains exist on two sides per the plans. According to the blueprints the slab is 4" thick with a 4" bed of gravel under that, no barrier between the two.

A 1year Accustar test, located in the basement at a height of 60" indicates an average level of 9.2 pCi/L.

We have purchased a real time (well, almost) detector and installed it in the upper level. The levels indicated there were in the low 20s pCi/L. I cracked a basement window 1/2" and the level has been steadily decreasing, leveling at around 6.5. That tells me that we may have a "stack effect" thing going on, that the open window provides some relief for the evident pressure differential. Today is very windy and the hourly level has risen to 8+.

I have identified several likely areas of ingress:

A sink drain stub has a 15" square hole cut in the slab around it (don't know why that is because the nearby toilet drain stub is not like that). The dirt pattern on the underside of the board that was covering it tells me that air/gasses have been rising from this area.

No sealant exists around the well pipe penetration.

Various cracks exist in the slab.

So, for a start, I'll seal these things up and see if readings change. I may place the monitor over the 15 x15 "pit" to see what's there.

I'm not sure how the wood foundation plays into all of this but I would imagine there could be ingress possibilities between the wall and floor.

https://imgur.com/a/hJEKk
 
 

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