Originally Posted by ole81
I appreciate all the input.
\Unfortunately, virtually all manuals are written by the engineers who develop the system, and are never reviewed by new users.
I think it's a safe bet that the plumbing system is a retrofit and not Airstream original so the manual wouldn't help you anyway. I say that because you do not have ball valves with lever, oval, or wingnut-style handles, where "handle in line with the pipe" equals on, and "handle crossways to the pipe" equals off, and all you need is a quarter-turn to go from fully open to fully closed. Instead you have a gate valve with a round handle, that you can't tell at a glance is open or closed, and requires several full turns to go from open to closed.
If you rework your plumbing system, use ball valves exclusively; get rid of the gate valves.