Attached is a picture of the left lanyard pull viewed from behind the driver's side front wheel on my coach. There is another one on the passenger side as well. You can pull these any time to remove moisture. I use an awning pull hook and do it every 6 months or so. I've yet to see any moisture come out so I guess my air dryer is working properly.
Your coach also has a Haldex Air Dryer/Filter located at the rear of the coach (mine is above the rear axle) that must be changed at specified intervals, depending upon what model Haldex is installed. If you do a search on the forum there is an excellent set of instructions for changing the dryer. If you are not comfortable working under the coach you may want to have that done by a professional.