[pgmetgud]

Hi everyone, I am making an "automatic tank full alarm" wherein I am using two thin graphite sticks (taken from two pencils) as sensors. One end of each stick is dipped in water tank. Other end of each stick is connected to + and - terminals of a 9 volt battery. That is how the circuit is supposed to work ( the circuit makes sound using a buzzer whenever water surface touches both the electrodes). I tested the circuit and it works well. But, is it safe to dip those two graphite rods in drinking water? Won't it be toxic?. As far as I know, I guess it must be safe because graphite is only a form of carbon. But, just to be sure, can anyone please confirm with surety that graphite sticks dipped in drinking water are safe? or is it toxic?

[Arkcon]

To be absolutely certain, you can look up the ingredients of pencil lead -- its not pure graphite, or even a mixture of graphite and clay, buy may contain a number of other substances.  You can also consider, the electrodes are only in the water when the alarm goes off, so the duration is short.  In my experience, if you use graphite electrodes in a salt solution for days the anode tends to be consumed by some process.