I need to stub a 3" PVC pipe through the foundation wall for an exterior air intake for my fireplace. The wall will be formed and poured tomorrow supposedly. Is there a special sleeve that should be used, or just use another piece of PVC? From what I've read, the sleeve needs to be 2 sizes larger than the pipe going through it. So that would mean a 5" sleeve in my case. Unfortunately, I don't believe any of the big box stores carry anything larger than 4". Area wise, 2-1/2" I.D. pipe with 4" sleeve would suffice, but I'm not sure how common 2-1/2" pipe is.

 

I would try to find a piece of 6" pvc or sewer pipe and cut it exactly 8" long and have the concrete guys set it in the wall forms where you want it. Assuming the walls are 8" thick. If the pipe doesn't have to be sloped a 4" sleeve might work. I would always recommend sealing between the pipes when done.