I'm planning to build a DC based transistor switch using my arduino for detecting the sanitizer level in the tank. Using the following example, http://www.circuitstoday.com/water-level-controller-using-arduino .

My question is if sanitizer (70% alcohol) would be conductive for my design to work ?

 

As far as alcohol yes.The conductivity of isopropyl alcohol (which is commonly the major component of rubbing alcohol) is typically 6 μS.m−1, so it is very low (typical value for a metal would be multiple millions of S.m−1!). By the way...
Technically, nothing "doesn't conduct" electricity (i.e. nothing has a conductivity of 0.00000), but some materials have much lower conductivities than others

 

The pKa of isopropyl alcohol is 17.1; water is about 14 (https://chem.libretexts.org/Bookshe...istry)/Fundamentals/What_is_the_pKa_of_water? ). The major contributor to the mixture would be ionic contaminants in water.

For the TS, if your invention will detect deionized water, it will detect the mixture.