 you have biofilm that's already growing in that plumbing system that there's no amount of chlorine or bromine or sanitizer in general that can get in there and penetrate those outer layers of the biofilm. So if you want a hot tub, instead of sitting there pouring so many different chemicals into your hot tub and just you're spending not only a lot of time, you're spending a lot of money, and who wants to soak in a hot tub that's full of chemicals? So our goal is we recommend purging your hot tub every six months