the red-handled valve in the pic w/ the tp roll is the supply line for the toilet.
"de-winterizing"...depends on how it was winterized. if the lines were simply drained, or blown out w/ air, all you gotta do is close the drain valves. If antifreeze was pumped in, you have to flush all the pipes. If antifreeze was added by pouring it into the fresh water tank, and pumping it through the lines...you need to flush out the fresh tank. (real pain in the ....).
'73 Safari 23'
'00 Dodge Ram 1500 4x4 QC