Spray Foaming a Basement Sewer Pit
brooklynite2
| Posted in General Questions on
In keeping with the guidance provided elsewhere on this site, I am about to insulate the interior brick of my basement with closed cell spray foam. Right next to this brick wall is my sewer pit. The pit gets humid during wet weather. That humidity builds up on the underside of my pit door and encourages mold growth. I also have high radon readings in the pit. The pit floor is concrete, save for the two cleanouts.
My intuition says I need a vapor barrier over the pit floor. I’m looking at the pit and thinking…if I cover the two clean outs, can I just coat the pit floor in the foam and solve this problem? My basement might still have radon afterward, but hopefully not as much. Is my thinking sound? Or will this win me a Darwin Award for some reason I don’t yet understand?
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Replies
I'm not familiar with the term "sewer pit." There are lots of local terms that aren't used everywhere. Is this a sump pit, with the two "cleanouts" being the openings for the perimeter subslab drain pipes? Is there ever standing water in the pit? What sort of lid does it currently have? Please provide further description.
If this is a sump pump, the usual thing to do is to cut two half circles to act as lid pieces, then cut some holes in between (with half of the hole in each piece) to clear any pipes or wires. Places these into the top of the sump to act as a barrier. It's not usually necassary to seal things here, but if you have radon issues you could put a gasket and a vent pipe to the outdoors. I would NOT spray foam this assembly, but you could use some rigid foam (this is a job for XPS) to insulate the lid pieces I suppose.
If you have sump with a sewage ejector pump in it, those are REQUIRED to be sealed, and should be vented too. You can get all kinds of nasty stuff from those, which is why you want them sealed. The sealed lids are factory assemblies on every sump I've ever seen, and they seal quite well. I would NOT spray foam these, either.
If you have anything else, especially if it's some kind of free standing tank, then I'm with Peter -- we need more info.
Bill
If we were talking about an actual sewer pit that filled with human waste I doubt the complaint would be “smells moldy”.
Please tell us more about your basement. Seems to me a brick basement would be somewhat unusual is it possible the basement is concrete block that would be more common.
Generally spray foam on the interior of a basement is best limited to irregular surfaces like rubble stone walls. Anything flat like brick, block or concrete is better covered with foam sheets.
Without installing a vent system to remove the radon it seem unlikely sealing the pit will change anything. The radon will find a way in unless you remove the radon. When they install the system they will seal the pit but not to keep radon out of the house but more to stop the radon fan from pulling air from the basement so the fan is pulling radon from the ground and not air from the basement.
Walta