I think my vent stack is plugged; I think this because the toilets sound different while flushing than I think they should, and I hear a knocking in the wall when a sink or toilet is flushed. Normally I would go up on the roof and look in the vent stack, but my roof has a steep angle and is not walkable. I realize I could use roof jacks, but I'm hoping I can avoid it.
What I would like to do is go into the attic where there is plenty of room to work and cut the vent stack into two halves so I can look in it that way (The vent stack is PVC). After checking for blocks and fixing if necessary, I would re-attach the stack with a rubber coupling meant for PVC pipe, or if that's discouraged, weld a PVC coupling to re-attach the two halves.
Would my idea be acceptable? I can't see any functional problem with it, but I'm wondering what an inspector might think years down the line, or if it's against code.