Question: How to seal large gaps in foundation around sewer pipe?
I’m a homeowner in the San Francisco Bay Area and sometimes noticed dampness in my crawl space. The home is about 20 years old on level gound.
I’ve tracked it down to rain/sprinkler water coming thought the hole in the foundation for the sewer main. It seems to be a 4″ ABS pipe with a very roughly cut hole (about 4″ gap in the both sides of the pipe) in the concrete a foot or so below ground level (outside the crawlspace). I’m wondering what the most appropriate way to seal such a hole is?
I though of filling the gap with a rigid cement might be bad for the pipe. I had the idea of putting a 5″ ABS pipe around the 4″ ABS, and sealing the outer sleeve with something like fiber reinforced cement, and using lots of silicon caulk between the outer and inner pipes. A little detail seems to be 5″ ABS pipe can’t be found. I also thought of filling the foundation gap with urethane foam sealant in a can, but don’t know how the ABS would react or if the foam would survive covered with soil.
It would ne nice to fix things for the next 50+ years.
Replies
find a way to keep rain/sprinkler water away from that area.
If the pipe is only 1 foot below ground and water comes in here when it rains/ the sprinker is on, then its just water runing down hill via the easiest route. Trying to plug that hole from the inside will probably not work over the long haul unless you keep the water away from it.
Ideas are: pitch the ground away from the house, move the sprinkler so it won't get the few feet around that area wet, and so on.
Plugging up the hole on the house will then be mostly a cosmetic issue once you have remedied the cause of the ground water.
Hope this helps.
By the way...
Ground water management is a big deal in the areas with basements & freeze thaw cycles, but that probably isn't much of a concern for you in SF! We that do live in those areas try to keep all water 3 to 10 feet away from our foundations to keep them healthy.
From the inside of the crawlspace, clean out around the pipe as deeply as you can...try to clear the full thickness of your foundation, if possible.
Wash out/brush out the hole to get clean concrete. Clean the pipe as well. After the concrete is clean and dry, a bonding agent may help, but I'd consider it optional.
After the concrete bonding agent was or was not used, I'd full the area between the pipe and the foundation tight with hydraulic cement. Mix it stiff, cram in some, use a stick to push it deep in the hole. Work around the pipe several times until you've filled the space to full depth.