Quote Originally Posted by joecus View Post
Hi Janet - I read this quote and wanted to ask you why a high cya is important to a pool that gets a lot of sunlight. That is the case with me. Also, I assume I could use the "shot glass" method to test my cya, is that correct?
Higher CYA can protect against loss from sunlight but you need to run the FC higher to compensate for the chlorine that becomes chemically bound to the CYA in the water and is not available as a sanitizer. Net effect in some pool is lower overall chlorine usage and in many cases chlorine does not need to be added daily to maintenance becomes less. However, all pool are differnt so YMMV.
As far as 'shot glass method' for cya, yes but it is only really useful if your CYA is testing at 100 ppm to see how MUCH over 100 ppm you are.

Since you are the third poster to post a pool problem in this thread perhaps the MODs would be kind enough to break it off into it's own thead or combine it with one of your other theads to avoid confusion!