Product review (5 stars): Do Not Use Distilled Water
I was having the same problem other posters were regarding the Add Water light.  When I first purchased the unit, I used tap water and did not have any problems.  Then as soon as I put in Distilled Water, I would get the "Add Water" light and the unit would not work.  As soon as I went back to Tap Water, I have never had a problem....you may think this sounds nutty (I sure do) but for some reason it can detect Distilled from Tap....