Mike, here are the pix I promised; as noted, they advise purging at least monthly - admittedly I haven't followed that schedule, but the coach and air system hasn't been used much lately. My set is in the streetside rear "bay", but many models may have them elsewhere, including the generator compartment up front. As far as that accessory air port goes (next to the 4 purge valves), having it in that rear bay is a super pain if you are a tow truck driver trying to hook your truck air up to the coach.