Sizing a radon fan

Hi All:
I moved into a new house that I built a couple of months ago. I bought a safety siren radon meter and let it do it's thing for about a month now. My readings are in the 5.6 area.
My basement is approximately 1800 sq ft., before the masons poured the slab I put two 3" perforated pipes into the gravel base in case we had a radon issue. I also had the plumber run the radon vent pipe from the roof down to the basement so I can tie them together. A couple of questions:
- How reliable/accurate are the readings from these ~$100 radon units? - Is there a formula that tells me how many CFM I need to draw based on square footage, current radon level, etc.? - Should I just seal off the sump pit, or run it into the other two 3" PVC lines running to the roof? Is a piece of lexan cut to fit and some polyurethane caulk good enough? - Given the current state of the basement (two radon pipes sticking out of the slab with a shoddy little cap on each, plus an open sump pit), should I try piping everything without the fan to see how the levels change?
Thanks,
-Marc
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I found the ppl at Infiltec (540-943-2776) quite helpful, and willing to talk.
I have one of those radon units. It pretty much matches the readings I got with the mail-in samplers. (Our levels are around 16.) Also, it does go to 0 in an wooden outbuilding.
Beyond that, we still haven't done anything. Technical issues, other problems, blah, blah, blah.
I'd like to see your results, if you feel like posting them when you're done.
George
On 9 May 2007 20:41:34 -0700, " snipped-for-privacy@gmail.com"

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I wonder if one had a interior french drain system that drained to daylight say near the street if radon levels would be less.
our neighborhood is a hot spot and we could use the drain system, wnder if it might fix both issues?
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