Groundwater leak through basement wall pipe penetration

[dbdoug]

Hi, first post. The attached photos show a leak where the main PVC waste pipe penetrates the CMU basement wall and heads toward the septic tank. The leak looks dirty, but It's not smelly. I don't have contact with the former renters, so I can't ask them if leaking occurs only after a storm. The wall is a gable end wall with no overhang - see photo. The wall faces the direction from which storms prevail. This morning I dug it up outside. It hasn't rained here lately. The dirt is dry, there's no sign of a leak and no smell. Am I right that this is very likely a groundwater issue, and not a leaking sewage issue?

How do I fix this? Dig the trench deeper (and wider?) and fill below and above the pipe with gravel or crushed stone to relieve hydrostatic pressure? Would it help to dig a shallow pit above the pipe, maybe 6' x 6', lay a sheet of poly in the pit, seal the poly to the wall, and backfill, to divert stormwater away from the pipe area? Once the spray foam is removed, what's the best way to patch and seal the hole in the CMU wall?

Dan

 

[PapaDisco]

Hi Dan,
I'm trying to solve the same problem on my project. After several heavy rains the ground is saturated and water follows the pipe in. Sounds like your leak is groundwater as well (no smells).

Trenching and backfilling with gravel will only work if you also provide a way out for the water. If the low point is where the pipe enters the building then the gravel will only make the problem worse.

The challenge is getting a water tight seal at point where the pipe goes through the wall. In my case, the original installers just packed that gap with miscellaneous rags; which eventually saturate and the leak pours on in. I suppose some sort of dense, paraffin soaked rope, like an oakum or something, might do the trick? And then a heavy petroleum based foundation sealer on the outside? Hopefully someone on here has a magic formula.
In the pics it looks like someone tried to seal the space around the pipe with expanding foam? Foam is good for filling gaps, but not great at water tightness.

I've got my pipe dug out now, and am going to spend time getting all the surfaces cleaned for whatever goo I end up packing in there. If anyone on here has a magic formula please shout it out!

 

[Sponsor]

 

[Reach4]

The attached photos show a leak where the main PVC waste pipe penetrates the CMU basement wall and heads toward the septic tank. The leak looks dirty, but It's not smelly. I don't have contact with the former renters, so I can't ask them if leaking occurs only after a storm.

Are you the new renter, or the owner?

I think you will want to use some Polyurethane sealant and/or hydraulic cement. Hydraulic cement is cheap, and you would use a lot. You could try both... use up a tube of polyurethane sealant, and then a bunch of hydraulic cement outside of that. Both will cure under water! Hydraulic cement expands a bit as it cures, vs most cements which shrink a bit as they cure.

These are expensive 3M polyurethane sealants... one cures slowly, and the other cures really slowly. They are well respected and made for boats.

3M 4200 vs. 5200 Underwater Sealant: Stop Any Leaks

3M 4200 vs. 5200 Underwater Sealant: wondering what sealants are suitable for your boat? Calm down, and both will provide superior solutions without emotions.

www.boatingsports.org

 

[GReynolds929]

Bentonite would work also.

 

[Reach4]

Bentonite would work also.

How does that work? Does that come in a bag as a powder or granules?

Do you mix that with water, in a 5-gallon bucket, to make a paste that can hold its form, and scoop and form it around the area like a putty? Do you make the mix looser, so it can slowly flow, and pour it into a form space you have made? Do you hold the powder in place with some kind of form, and then let it get wet after it is in place, from natural water coming?

 

[GReynolds929]

I have not personally used it. My understanding is mix it into a sticky clay and fill the voids around the pipe. It is used in well drilling, but I think they mix it a lot looser when adding to seal around the casing.