has anyone tried or heard of doing a gradual drain & refill cycle, instead of periodically changing the water? since i am committed to autofill, autodrain is a natural possibility.
around here, it costs $4 to fill a 500g hot tub and i might change the water every month. this is the same rate of fill as implied in dumping and refilling about 18g every night. not sure what this does to the average "age" of the water. perhaps it would not protect someone whose hot tub contains legionnaire's disease (?) and doesn't know (??), but could it work in practice?