That would be the one! With Wayne complaining about his air leaks, all those "extra hours" the aux compressor was running, more moisture than the Prevost dryer in the fjb can handle (along with improper maintenance of the air system from the previous owner) was entering the system. He will be chasing a few more valves before it's over. This valve is installed to stop the flow of air from the main tanks in the event of an air bag/line failure.