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Old 01-25-2008, 12:58 PM   #1
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Fixing 11" Hole in Concrete Foundation


Hi,

I have a small radon problem and before looking into mitigation systems I want to try sealing the cracks and the 11" sump pump hole in the basement foundation.

The cracks are no problem but obviously I can't just fill the sump pump hole. I'm thinking of covering it with a high gauge steel plate with puched openings for the pipe and wiring, using the concrete sealer to seal the plate to the floor and then covering the hole thing with a thin layer of grout.

This is my first house and I have never done any home repair before so I'm guessing at all of this. I haven't found a similar situation (found info on filling a hole but not on covering a below slab sump hole) so I figured I would ask if there is a better way to do this?

Thanks,

Robert

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Old 01-25-2008, 01:26 PM   #2
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Fixing 11" Hole in Concrete Foundation


that should work but you may add a vent pipe from the sump to the outside, one to vent any radon and second to provide air when the pump runs so it is not creating a vacuum

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Old 01-26-2008, 09:17 AM   #3
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Fixing 11" Hole in Concrete Foundation


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that should work but you may add a vent pipe from the sump to the outside, one to vent any radon and second to provide air when the pump runs so it is not creating a vacuum

Thanks! The hole is right near a wall so adding a vent shouldn't be a problem.
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Old 02-03-2008, 11:31 PM   #4
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Fixing 11" Hole in Concrete Foundation


I would skip the vent pipe out the side of the house. You could create a situation that applies positive pressure to the sump basket thus pushing more radon into the basement than previously. A proper vent pipe would extend up above the roof and then it will do a better job of creating a draw on the soil below the slab. But if your level is low sealing alone maybe enough.
Also a separate vent pipe shouldn't be needed in the sump basket for the pump, if you have a drain tile system.
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Old 02-04-2008, 12:52 AM   #5
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Fixing 11" Hole in Concrete Foundation


As far as the cover itself, I would use a nice, thick sheet of metal, with punched holes, but I wouldn't concrete it down. I would just use concrete anchors, then seal it if needed with caulking. The vent pipe would be good if you seal the discharge pump pipe, and no other air vents are in the metal cover.
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Old 02-04-2008, 07:55 AM   #6
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Fixing 11" Hole in Concrete Foundation


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I would skip the vent pipe out the side of the house. You could create a situation that applies positive pressure to the sump basket thus pushing more radon into the basement than previously. A proper vent pipe would extend up above the roof and then it will do a better job of creating a draw on the soil below the slab. But if your level is low sealing alone maybe enough.
Also a separate vent pipe shouldn't be needed in the sump basket for the pump, if you have a drain tile system.
The sump is below the foundation slab in a perforated pvc tube. I was told by the pump company rep that it is for removing ground water below the slab rather than for removing water in the basement (so once I seal the top there will be no opening going to the cavity below the concrete.

We had a reading of 14pCi/L. The house was vacant and weather sealed for a year. I'm planning on sealing all the cracks and the sump pump hole and then re-testing. If it is still above 4pCi/L after I re-test I plan in putting an inline fan on the sump pump vent and extending the exhaust above the roof line then re-testing again.

How does that sound?
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Old 02-04-2008, 08:08 AM   #7
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Fixing 11" Hole in Concrete Foundation


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Originally Posted by leroyme View Post
As far as the cover itself, I would use a nice, thick sheet of metal, with punched holes, but I wouldn't concrete it down. I would just use concrete anchors, then seal it if needed with caulking. The vent pipe would be good if you seal the discharge pump pipe, and no other air vents are in the metal cover.
The sump pvc tube extends about 1/4" above the basement floor. The sump itself is in the dirt below the foundation and I have been told it is for removing groundwater from below the foundation rather than for removing water from inside the basement. I want to completely seal it to remove the open path for radon to get in the basement so punching holes in the plate wouldn't work.

My biggest concern is what happens if the sump fails? I wouldn't even know that it stopped working since I can't hear it now (without the cover!).

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