Why would PVC pipe break under basement floor

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Patrick752

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Hello all,
We are under contract to buy a home with an ICF basement and a radon mitigation system (sub-slab pipe and fan). An inspection found that the radon was not being mitigated by the fan. More inspection found that the fan had stopped drawing enough air volume. Even more searching found that the PVC blackwater pipe for the basement laundry had broken under the slab causing the water levels under the slab to rise and block the radon vent pipe. The sellers are in the process of having this fixed.

Our concern is, what would cause this PVC pipe to break under the floor? The house was built in 2003. The pipe was not broken in 2012 when the radon vent pipe was installed. I know very little about ICF basements or foundations in general but if this pipe is broken, should we be worried about the other pipes under the slab?
 

Jadnashua

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PVC can break when stressed beyond its capabilities. Being underneath a slab means there isn't as much thermal expansion/contraction going on as it might have above ground. The stuff does expand and contract a fair amount with temperature changes. If there's not some movement accommodation when the line comes up through the slab, that becomes a fixed point, and the rest of the stuff will still want to move. that can cause stress failures. The line should be sleeved with some foam where it comes up through the slab.

While big ones aren't that common, Illinois does see some earthquakes.

An ICF foundation wall is essentially a poured, reinforced concrete wall where they left the forms there (the foam). IT's a great way to make an insulated wall. STrength is not an issue for it as long as it was originally sized properly (the blocks come with various amounts of insulation and thickness to allow more or less concrete in between the outer skins of foam).

TO be able to collect the radon, the pvc pipe below must be perforated. If there's a high enough ground water table, those pipes will get wet. That can play hell with trying to suck out any of the gas if the pipes end up full of water.
 

Master Plumber Mark

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we run into this on occasion....... its much worse when the opposite happens and the drain line under a basement slab
breaks and the water that should be going to the sump pump system leaches over into the sewage pump and the sewage pump is throwing tons of clear water into the sewer system---thats a hell of a mess to deal with

its either due to expansion in the ground or just minor earth
quakes moving the lines enough to stress crack them
 

Patrick752

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UPDATE: So it turns out that the radon mitigation company is taking responsibility for this damage. Apparently in 2012 when they drilled their core and excavated a small amount of gravel to create an area for a vacuum under the slab they accidentally broke this black water drain pipe. So all the water from the laundry has been draining under the slab for 7 years. Thanks for the responses.
 

Master Plumber Mark

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UPDATE: So it turns out that the radon mitigation company is taking responsibility for this damage. Apparently in 2012 when they drilled their core and excavated a small amount of gravel to create an area for a vacuum under the slab they accidentally broke this black water drain pipe. So all the water from the laundry has been draining under the slab for 7 years. Thanks for the responses.


They must be a really upstanding company to take responsibility for this after 7 years has passed.....
most places would tell you to take a hike after one year.....
 
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