Product review (4 stars): In this case I suppose no evidence is good. I do recommend adding the product after your ...
Hard to really know if this stuff is working or not. I've been using it about 2 weeks in an evaporative humidifier that goes throught about 8 gallons water in a day. The tanks remain sparkly clean and I don't see buildup in the filter. In this case I suppose no evidence is good.  I do recommend adding the product after your tank is full and not before. If added before it causes a lot of bubbles that foam up/overflow.