The most obvious way to estimate how full your water tank is....is to tap it on the side and listen for a difference in pitch....below the water level has a lower pitch than above. But this is a guesstimate approach.
By using a combination of sinkers, floaters, and fishing tackle you can arrive at a more accurate....and visually interesting way of keeping track of you rain water level in the storage tank.
Water tank with lead sinker determining the inverse water level within the tank. That is when the sinker is at the bottom....the water level is at the top.
A sinker of the same weight as the one outside the tank is attached to floaters ....to ensure this sinker stays with the changing water level. (In order to prevent the lead from making contact with the water....if the water is used for drinking purposes, it is wrapped in plastic.)
The floaters and covered sinker are connected to the external sinker via fishing tackle....and then dropped into the tank.
Make sure the nylon fishing tackle can move freely across the edge of the tank....and close the lid. Then watch as your water level go up and down...
Anyone tried this?