If I have grasped the CYA/FC relationship notion:
1..that as CYA increases, there is less HOCl available/free/unbound for use as a sanitizer and/or algae controller,
2. and that HOCl is really what I am trying to maintain by adjusting FC,
3. and the HOCl level decreases (non linearly) as pH rises,
4. and that the available/free/unbound (not sure how it should be labeled) HOCl should be at least above .011 for sanitation and maybe ~.05 to prevent most algae.
When I became a TFP member/believer I began a spreadsheet containing all my test results and what I have added to my pool.
I found the following formula: .31*FC / (CYA-(1.8*FC)), but I think that it only approximates the actual HOCl. And it doesn't include any pH level impact. Is there a practical use formula that I can build into my spreadsheet??..I am hoping that it isn't an iterative calculatio.