I am running the filter as I add fresh water to the pool. I drained about 6 inches because my salt level is 4800 ppm. I have a 24500 gallon pool. I intend to circulate for the appropriate time, then drain again by backwashing (I haven't figured out how to drain from the main drains--pool builder never went over). I hope that the foot or so in new water will bring my salt levels down to around 4000 ppm.