Water valves and underbelly tubes

I have the service manual for a '72 but it doesn't go into detail about what the water valves do in the different locations. It also doesn't say where all the tubes exiting the bottom come from.



Has anyone made a list somewhere I haven't found yet? I have 3 under the galley, one by the hot water heater in the cabinet and 2 or three in the rear by the battery.



For example, looking under the trailer today on the curb side, midway just under the wrap, I saw a rubber hose that was disintegrating. I have no idea where it comes/goes or what it does.



Thanks. Any help is appreciated.