I am considering installing a rainwater tank for garden use. An
accessory that has been suggested is the "Levetator" water level
indicator. These types of devices are purely mechanical and use a
float, counterweight and pulley to lift a plastic ball on the outside
of the tank. This moves up and down as the water level rises and
falls. Has anyone had any experience with these systems? In particular
I would like to find out how reliable they are and if they are likely to
jam up when left exposed to the elements. Also how difficult are they
to install?

Regards
John Charles