I am using the BBB method and my last fill was about 3 months ago. I used dichlor initially to achieve ~30ppm CYA. I tested recently and found the CYA is less than 10ppm now. I remember seeing that CYA needs to be periodically added to maintain its level but forgot about it.
My wife has been experiencing skin irritation when using our hot tub in the past few weeks. I understand that high CYA levels require higher FC levels to maintain sanitation. My question is the reverse, that is do low CYA levels result in effectively higher FC levels. For example, if I add bleach to 4.5ppm at <10ppm CYA, is that effectively a much higher FC level that could be causing skin irritation?