Water Level Alarm schematic
click the picture to see full size

This is a circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath, cold storage tank or even a big aquarium. How this works ? its simple, the circuit will trigger with any fluid with a resistance under 900K between the maximum separation distance of the probes. 4011 IC’s are cheap and easy to find, so you wont have any problems building this project.

Water Level Alarm: [Link][Via]