I have an Artic Spa (360 gallons). It has ozone and SWG. I only use the Artic Spa chemicals, basically Boost (cholrine), Refresh (nonchlorine shock), and Ph up and Ph down).
When I test the water the CYA is at 80? I never added CYA nor used any products containing CYA. It must be coming from my pool as people (mostly kids) go from pool to spa to pool. My pool CYA is at 50.
I understand CYA as it relates to pools, but how about hot tubs? How high can I let it go before I need to drain it?