My vent stack boots are in very bad shape and the rain must have been combing into the attic. The pipe was 3", so I bought a 3" to 4" rubber adaptor from Lowes and put it down, I think it should work. Anybody else try this? The alternative is to remove the boot (and plate) from shingles and replace. I have a 2" vent stack also. This one doesn't look to be leaking yet. I don't think there is a 2" to 3" adaptor readily available, so I'm looking for ideas.