I traded in my 40 foot Monaco Camelot recently. I was concerned about 40' restrictions so I measured the rig, the actual length is 39'6". Short enough to be legal, but long to to have white knuckles.
We went to Glacier last early summer. Took the red car tour. It was well worth the money. Guide had worked there for about ten years. Saw and heard stuff you would never know if you drive by yourself.
Sounds like you have set the valve for "tank fill". Check in your utility cabinet for a quarter turn handle, it should be marked for tank fill in one position and city water (or something similar)in the other. Post back so others can learn from your ...