Here is a how to on how I made a floatpulley water level indicator for my culvert rainwater cistern. This is not a reverse level indicator that shows the water at a reverse level, this uses a float and pulley to give you an accurate measurement without having to tap, feel, or look in the top of the tank. I positioned this one where I can see it from a window, for viewing during a rain. Thanks for watching\rbr\rbrFor the mechanism detail you can skip to 3:53 or so to get the details of the system.