Quote Originally Posted by mas985 View Post
Theoretically, it should be exactly the same. A 10% increase in CYA gives 10% more UV protection so the FC residual should rise by 10% countering the 10% increase in CYA (i.e. same FC/CYA ratio). So it should all net out to exactly the same % SWG setting and the same cell life. This of course assumes that it is only UV which is destroying the FC.

My own experience has shown that this is true and in fact, there may be a little extra benefit with higher CYA. In some cases, when I went from a low CYA to a higher CYA, I was able to actually lower the SWG % settings to achieve the higher FC levels. Based upon this, it would appear that the UV protection properties of CYA are somewhat non-linear.
In reference to my question, the variable is the desired CL level, not the CYA level. Assuming CYA is kept at the top of the recommended range for my SWCG (80 ppm), do you think there would be any difference in swcg% settings whether maintaining CL at 4 ppm or 8 ppm?

Thanks.