So helpful!

My system is labeled, perhaps incorrectly, with liquid and vapor valves. Here is a picture.

Actually, here is a better picture.

The valve labeled ”Liquid”, if it goes to a pressure regulator, is most likely the fuel supply for your generator (my best guess). The valve labeled “Vapor” is most likely serving your appliances. Getting under the rig on a creeper will tell the story as you physically trace the line in question.