does your fresh water tank look like a galvanized torepedo? if so, it's almost certainly a pressurized system. you fill it with water, then pum it full of air to provide water pressure. you should see the air fitting on the fill tube. in my trailer all that stuff was trashed by the previous owner, ao i'm rebuilding mine with a demand system (water pump and plastic, non-pressurized tanks).
also, i can almost guarantee you that you don't have a grey water tank. i couyld be wrong, but i believe airstream didn't start doing those until the mid-sixties.
so, what to do next? hmmm... fill her up with water and air and look for leaks!
