Thank you for the information and the photograph. I did contact my local inspector. 12" below the soffit, vented or not is the code requirement for my locale in Indiana. The inspector mentioned sloping the pipe down for water drainage. The instructions call for a 1/4" slope up per foot of run...
I know there have been several posts on this topic. I have the heater but it is not installed. It would be much easier to vent through the wall in my case. My 2.5 car garage is attached to the house with an unheated room above.
The main question is the clearance needed for the 4 inch vent...