stvee

Hi, I have a wood fired hot tub. with a molded plastic inside, an external stainless steel heater and a sand filtration system. The water still gets manky ( and probably full of bacteria) after a few sessions........ People use it daily and ideally i don't want to change the water more than once a week. What chemicals do you recommend i use to keep the water clean, ideally NON chlorine as that will corrode the heater? Many Thanks- Steve