Here's the piece that everyone's leaving out:

At higher CYA levels, yes, it's true, you need a higher FC level to maintain sanitation.

BUT what happens is that you get a residual of chlorine that generally remains, so you are only chlorinating for the extra you need.

Say, for example, your CYA is 110. The suggested FC for that CYA is 8 to 15 ppm (and shock at 25). You should find it very easy to keep your FC in this range and not use any more chlorine on a weekly basis to maintain it than you use at lower CYA and FC levels.

Actually, your chlorine usage may go DOWN because the CYA gives you such a high residual of chlorine.

One of the moderators, Aylad, leaves in the Deep South. She gets lots of factors that drive FC down (consuming her chlorine). So Aylad runs her pool consistently at higher CYA levels than we Northerners do--80ppm. Since Aylad has her FAS-DPD test kit, she can test higher levels of chlorine easily--and keeps her FC level in the 5-10ppm range. This allows her to avoid constant monitoring and chlorine additions several times a day.

But since I live in Northern NJ, I tend to keep my CYA in the 30ppm range for the early part of the summer, running it up to 40-50 when we approach the Dog Days.

CYA is a two-edged sword. It slows the metabolizing of chlorine, so it doesn't burn up instantly in the ultra-violet. But it slows down the metabolizing, so you need more chlorine. Still, if you follow the guidelines AND have the FAS-DPD test, there's no reason not to run higher levels of CYA. It CAN make your life easier if you have VERY intense UV (at lower latitudes), and/or lots of organic material you are metabolizing.

CYA should NEVER be used in an indoor pool.