try and keep mine between 60 and 80 ppm because that is what the manufacturer of my SWG recommends and a call to their tech support line told me that it is recommended at that high a level with a SWG because of the 'superchlorination' that takes place in the cell whenever it is generating chlorine. Don't know how true it is but I do know that when the levels are in that range the pool water sparkles and my FC levels stay pretty constant. I have a leak which the builder has yet to fix and my cya dropped to maybe 20 over a 3 month period and I started having all kinds of problems holding chlorine in the pool once the cya got below about 40 ppm!