In the photos, you’ll see a vent stack on the ridge. I’m fairly sure that is acceptable (correct me if I’m wrong). But, the next photo shows a plumbing stack beside the ridge vent. I’m concerned about the ridge vent having a negative effect on the draft of the stack vent. I haven’t found anything saying how for a plumbing stack must be from a vented ridge. Is it OK as is or is their documentation (code or otherwise) stating that it’s not right?
I would say no problem. They are both venting out. The stack looks to be sticking up a good amount and is way less likely to leak at the peak than at the bottom of the roof. I would be a lot more concerned if it were near a valley.