Need a little help in filling the knowledge gap I have.
I get that you need some measure of CYA to keep from losing your chlorine to the sun. Having that measure of CYA requires you to have a higher level of chlorine then you would usually have if you did not have that measure of CYA.
What is escaping me is what happens to the chlorine that is being "protected" by the CYA? Does it eventually get released and therefore able to be used to sanitize the pool? Or for a given CYA level, is a certain amount of chlorine needed before it is effective. In other words, with 0 CYA and 5 ppm of chlorine, it looks like all 5 ppm of chlorine is available for sanitizing. So then theoretically (and I ma making up numbers here) with a CYA of 30, and the same 5 ppm of chlorine, some part (lets call it 3 ppm) of that 5 ppm is being "protected" by the CYA leaving less for sanitization (which is why you need more chlorine when you have CYA - right?) resulting in 2 ppm or chlorine being avaialble for immediate use. What happens to the 3 ppm that is being protected, and when (if ever) does it get used?
I am going to convince a relative to go the BBB route or at least leave the pool store, but I know this question will come up and I want to be prepared. I pretty much understand and can explain the rest of what we talk about here, but there is a gap in my knowledge that I can not seem to close on my own.