Radon and Sub Slab Drainage
Asked this over at JLC, I am still interested in opinions on question and comments…
I am going to use the formadrain in a few weeks. I am going to use the interior formadrain for radon abatement (interior formadrain connected to a 4′ PVC passive system to vent out the roof at first, then fan driven if the radon numbers come in high after the house is completed).
I was looking at one of the formadrain details where the interior drain is attached to the exterior perimeter drain through the footing for drainage of any possible interior bulk water beneath the slab. I like the idea of this detail, but then I was thikning about my radon abatement and the fact that the perimeter drain will go to daylight.
I am wondering if this connection between interior and exterior formadrain through the footer and their subsequent daylighting will reduce the ability of a passive or active radon abatement system to acquire any kind of pressurization to remove radon.
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For a radon abatement system, I don't think you want to connect the interior footer pipe with the exterior footer pipe. You want to depressurize the sub-slab gravel -- you don't want to be sucking air through the drain that leads to daylight.