I'm helping a friend open up his pool and make sure his tests and water are in good shape. Things are looking very good, but CH is a bit high. But from what I remember last year (when we took this pool from green to clean), CSI must also be looked at before you determine if you really need to replace any water to lower it.
First some background.
24,000 gallon gunite pool, about 15 years old I'd say. Manually dosed (no SWG).
CYA: 0 (adding CYA to get to 40, so doing that way)
For his pool, we see CH as ideal around 300. But his CSI is 0.25. If I understand poolmath correctly, until you are below -0.6 or above 0.6, he is still ok and doesn't need to change out any water.
If this is true, why not? What does CSI tell you, and why is it not an issue, even though it's way above the range?
Thanks for the (upcoming) chemistry lesson!