While on my roof cleaning my gutters, I looked down my main vent stack and saw sitting water about 3 feet down. I originally thought I had a blockage, but after crawling in my attact, I think the problem may be due to an incorrect pitch.

A 5' vent pipe goes through the roof into the attact, then connects to a 90 degree connector for another 5' run. This second 5' run slopes up, significantly causing rain water to become trapped in the 90 degree connector. This 5' section of pipe slopes up almost 1 inch per foot, causing the water build up on the 90 to almost completely block the air from exiting the house, almost acting like a trap. I stuck a pipe down the roof vent to see the depth of the water in the vent and it's close to 3 inches, the 90 elbow is for 4 inch PVC.

Is this pitched incorrectly ? If so, it looks like I could easily correct , since the vent is made of PVC.

Thanks in advance for any help!
John

Jack the horizontal pipe up at once to give it slope back down to the main. You are correct, you have a trap that's blocking your vent rendering it usless.
If you do not address this problem at once be prepared for drainage problems in the future. Good luck, Tom

Thanks speedball1,

My game plan is to do just that by cutting a section out and joining with a connector after properly adjusting the pitch. I can't jack it up, then I'll have to deal with the roof flange and seal. It's PVC, so this approach should work.

Thanks again
John