Stormin Mormon wrote, on Sun, 29 Jun 2014 15:07:43 -0400:

Is the other end of the rope tied onto a float?

Yes. It has, literally, a chlorox bottle on one float, and,
IIRC, a more standard float on the other. I think one is
to shut off the house booster when emptying (for fire) and
the other is to shut off the well pump when filling.

I climbed on top of a neighbor's tank farm, and snapped
a lot of pictures, because mine, with two shared tanks,
seems to be the oddity.

The neighbor's whom I climbed in had six 5,000 gallon tanks,
all hooked up in series, but with the last two reserved
for fire alone (plus a 20,000 gallon cistern for fire).

I snapped a bunch of pictures but can't post them right
now as I have to run (maybe it will be a different thread
as this is getting a bit off topic from the "trucking"
aspect).