My natural gas hot water tank still uses black (ABS) plastic vents. Due to a building code change, these need to be replaced with System 636 pipes. The current abs plastic pipes go to the roof. I don't want to have to make holes all the way up 3 floors to replace the pipes, so as I understand most people change to sidewall venting when changing these pipes. However, the backwall of my townhouse where the sidewall vent would go has an air conditioner, a sliding door, and some meters (see picture). My understanding is that such vents have to be a certain distance from all these items, and there just doesn't seem to be any room. Is sidewall venting possible? Any alternatives that don't involve destroying walls?