It’s like a miracle.. So simple and gratifying. Now we can see how much water is left in the tank, right next to the stairs, in this little tube.

Just added a T fitting on the hose leading to the forward sink, with this clear hose leading straight up, which by gravity tendency to equalize water level, gives us the level in the tank.

Not so critical here in the Santa Barbara channel, as we (almost!) never run out of water, but it will be essential in arid places.. Say, Baja?