No pictures of the last one of the day no time just as the Sun had set. Real pain in the azz. Another fast food place. Irrigation POC inside the utility room, behind the humongous 160 gallon water heater. Another Suffolk special - no irrigation backflow that I could find (altho the building main had one on the 1.5 inch main).
No means of direct blowout port. Searched around outside the building, nothing there or in the valve box....that took extra time to find in the dark.
The way things were plumbed, I had to shut off the cold supply valve to the water heater, and close an ancient gate valve. Then "back feed" the air from an outside hose bibb through the inside plumbing and then out the irrigation pipe that disappeared into the building slab behind that water heater. At least there was a ball valve on the irrigation line and one on the hose bibb.