But if it doesn't show it in the manual as an example, he might not approve it . It would be more expense to run the vent pipe up the outside wall (as shown in manual examples) but possibly might get you that all important inspection approval.The more i think about this the more its bugging me! so if "stretch out" the air pipe to make it longer and then run it 12" down the wall so the opening is below the vent pipe the OAK opening is then below the vent pipe yeh ??
And as a side note; the 45 years I've dealt with inspectors, about half have known their stuff and half not so much. It's been a crap shoot. Wish you the best!