Spent $900 on a radon fan and the basement still reads high

Got a quote last fall from a local company to install an active radon system in my walkout in Mill Woods. Paid $900, they put the fan in the crawlspace, sealed the sump pit, and ran the PVC outside. Tested after a week with a digital monitor and it dropped from 250 to about 120, which is under the guidance but not the single digit I hoped for. Anybody else here dealt with stubborn readings and had to add a second suction point or upgrade the fan size?

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evanb872mo ago

Yeah I read somewhere that walkout basements are tricky because the soil gas can come in from the side walls, not just the slab. That drop from 250 to 120 is actually pretty normal for a first fan, most guys I know say you need a second suction point on the opposite side of the house if you're still reading above 100. Also check if the crawlspace is actually sealed off from the rest of the basement, a lot of people forget that the vapor barrier needs to overlap at the walls too. We had a similar issue and adding a small fan in the sump pit on the other end finally got us to the single digits, but it cost another $400.

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