Has anyone had a clogged plumbing roof vent pipe?

This has worked for me in the past. Ask the wife to stay in the rig by the sink just in case. You go up on the roof with a hose and take caps off vent pipe then stick hose down the vent turn on all the way. If there is a blockage the water will blow it back into the tank. Only thing to be careful of is that it doesn't come out someplace in the coach. That's where the wife comes in. Leave it run for a few minutes then see what you got.