This is my little spark of genius. It's a water gauge. I ran a line from the drain spout and connected it to the breather spout. The clear tube shows the water level in the tank.
Great Job ! I built the same "Gauge" on our 92 Jayco but left it inside the cabinet. There was no possibility to build it save from damages in the corner. This solution is much better. I like the old Siesta!