I'm doing research on SWCG's for spas. I've been looking at three portable ones, Spa Pilot, ColorChlor and Nexa Spa. The first two have an output rating of ~15 grams chlorine per day. The last one has a rating of ~100 grams per day. All at 3000 ppm salinity. The last one claims it can produce enough chlorine to sanitize a hot tub (~50 grams/day) at 1500 ppm salinity.
My question is, how much Free Chlorine (FC) will they produce in a 350 gallon tub?