[Richard]

This is where I am confuseded (as my three yr old once said). I always thought the air from the engine compressor via the desiccant drier goes first to the wet tank before it goes to the brake tanks. I assumed that somewhere in the desiccant drier or upstream of the wet tank is a check valve. There has to be a check valve because the engine compressor unloads and exhausts at the drier.