How can it work so well with 75% less chlorine?

SmartChlor is not a typical chlorine.  It will consistently maintain a 0.5 to 1.0 ppm free chlorine level. This would not be enough on its own; but with FROG minerals, it’s a perfect combination that kills bacteria 2 ways so you have a cleaner, clearer hot tub that’s wonderfully soft and odor free!