How to properly seal pipe exiting foundation

[bk82388]

Hi everyone, had a quick question in regards to sealing the waste pipe that exits my houses foundation to go out to the septic tank. Currently exits through the foundation wall and it was spray foamed around it to seal it. Not sure if that is the preferred method or not, but unfortunately a mouse or some other critter has taken the time to make a channel through the foam which allowed quite a bit of water into the basement last storm.

Should i just take a can of great stuff to the hole to fill what the critter did, or is there a better more preferred method for sealing this. I put a picture below so you all could see what I was walking about.

Thanks for the help!

 

[Dj2]

For small holes you can try steel wool. Clean the foam around the pipe, stuff steel wool then use caulking to keep it in place.

Another idea is semi soft flexible duct seal putty (not plumber's putty) - I used to get it at HD - which comes in 1 lb blocks.

 

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[Dgeist]

Most plumbing jobs I've seen around here used hydraulic cement for large voids. It's cheap, fast, and durable, but it's not a water seal unless you get it just right. The plumbers whose work I've been the most impressed with also followed up that with a flexible polyurethane or similar flexible caulking on both sides after the cement was mostly cured.

Polyurethane foam is great stuff (no pun intended) and is used a lot, too, but has its limitations. One of which (for closed cell) is that it has little structural value in this application, so don't depend on it to hold the pipe in place. Any expansion/contraction you have in that pipe or wall during seasonal changes may make gaps in the seal (just like with hydraulic), so make sure the surfaces are REALLY clean and mostly dry before spraying. A little dampness will actually help it cure better, though.

Another problem is that , as you discovered, a dedicated pest can chew through it easily if they're motivated. If you re-foam it, pull out the old damaged stuff if you can. You never know how much damage was done and it'll give you a chance to clean up any dirty or brittle cement.

Also, it's not UV-stable, so having it on the outside is usually not a good idea (ever wonder why outdoor foam use, common around HVAC penetrations, dark orange and brittle?). Don't use foam by itself on the outside. Here's an interesting suggestion from over at finehomebuilding: a roof vent flange with the seams sealed by roofing tar/sealant.
http://www.finehomebuilding.com/1999/05/01/sealing-a-drain-penetration-in-a-foundation-wall