Many lifestyle blocks obtain their water from roof collection. A common tank storage is a 25,000 litre plastic tank, generally with a corrugated surface (corrugations running around the circumference). What is not provided with these tanks is a water level indicator. Design and fully cost out TWO solutions to this problem, basically Mk I and Mk II, where Mk I is the basic unit, and Mk II is the unit with all the frills and add-ons for those with lots of money for whom convenience is a significant consideration. You must cost out all components and installation costs. Your design time is not a consideration here. You are free to use any combination of mechanics and/or electronics in your design