I will try to add three photos that show my confusion.
Our is a twin bed. Remove road side twin and look underneath and view city water inlet (top photo). Pipe runs down from inlet and makes turn to front of 'stream. Within a couple of inches of that turn, anther pipe els out from that one (this second pipe has a valve, currently in off position). This second pipe does a 90 degree down thru the floor. Not sure where it goes.
Now, don't move, just turn to the right and look down. (Second photo) You see, just this side of the closet, a pipe comes up from under the floor and rejoining that first pipe that lead toward the front, they both pass thru the wall into the underneath compartment of the closet.
Go to the underneath closet compartment and look down where those two pipes come in. (Bottom photo) The top one has another on/off valve and then rejoins the bottom one.
I am confused about the two pipes that have valves. Maybe they are the same pipe and just travel under the floor to make less clutter in the storage area...don't know but what in the world are they for??? Thanks for any advice other than "well, hell, turn 'em on and see what happens".