1) Place the Ultrasonic sensor at the top of the tank
2) connect the ultrasonic sensor to the arduino (check the circuit diagram for the pin connection)
3) connect the relay to the arduino
4) Program the arduino
5) In addition, if you want to display the water level using LCD, separate circuit has been provided, It's easy to add a LCD module to this project and monitor water level.
6) Power the arduino with 9v Dc supply.
Note: This recipe has not involved too much components and complex coding, any novice user whose having a little electronic knowledge is sufficient to successfully complete this project.
Arduino code for water level controller: