As alluded to above, real world pool owners that follow the TFP recommended level of having their minimum FC be 5% of their CYA level have found that higher CYA levels leads to less overall daily loss rates of chlorine and thus means running their SWG at lower output. There isn’t a lot of scientific literature (data) to back up the proposed theories as to why that is other than all of the anecdotal evidence TFP has amassed over the years. The higher levels of CYA just simply lead to more stable FC values. Since SWG’s have a finite operational life (roughly 8000 to 10,000 hours of chlorine generating time), running the cell in the most efficient manner prolongs it’s overall life. A properly maintained pool should give an SWG owner about 8-10 years of useful life.
In my own personal experience over the last 9 years I have found that as long as my CYA is above 70, I notice no excessive use of my SWG. As soon as my CYA drops to 60 or below, I start to have to increase my output % to maintain the same FC levels. I add CYA two times per year - once in early spring after the winter is over and right around mid-July. The sun is intense enough here that CYA naturally degrades and so I always know to check my CYA whenever my SWG starts needing higher output.
