Air configuration from tractor to trailer - baffling!

OK good to know, thanks! What is that valve called?

 

Quick release valve, but probably want to plumb it with the exhaust on the bottom when you replace it.

 

OK thanks, and yes I would just to keep the rain out. This other valve hisses air slightly when the park brake is released, it needs replaced also, what is this one called? It's in between the drive axles.