An ultrasonic sensor with an LCD display. The code works for a tank up to 5m tall.

My first attempt at an Arduino based project. The code was built based on the basic sketches included with the Arduino Sketchbook Examples. 

The sketch also pushes out the tank level to the comm port for any listening device.

 

I'm planning for the next generation of this to have multiple tank level sensors and include motorized ball valves for the house pressure pump to allow dynamic selection of water tank based on the level of the water in each tank.