Bear with me...some of you may wish you hadn't read my wonderings/wanderings once you get started....
If I understand correctly, the pro of CYA is that it helps keep the chlorine from burning off so quickly - especially when sunlight is present. Consequently, the higher your CYA, the more chlorine you need in your water to maintain clean, sanitized water. This is because some of the cholorine is "held" by the CYA? So, you have to add more cholorine to the water because some of the cholorine is basically rendered useless while it's being held by the CYA? So you first have to "fill up" (or saturate?) the CYA in your pool (ie have enough chlorine to bond with all the CYA) to the point that there is more chlorine than can bond with the CYA...leaving chlorine to kill the baddies in the water...?
But, if that is all true, does the chlorine that is being held with the CYA ever get released? And if not, it seems like CYA wouldn't be necessary - that doesn't seem like a stabilizing thing if it just grabs the chlorine and renders it useless... I'd think that it would be more cost effective to have no CYA so that all the chlorine you add is beneficial. Which is obviously not true. Which makes me think that the chlorine must get released by the CYA...which leads me to believe that I've got the process backwards. You "saturate" the water with chlorine and then the CYA holds extra chlorine? As the chlorine is used/breaks down in the water, chlorine is released from the CYA? BUT if that were true, than maintaining a higher chlorine load (when you have a high CYA) would be optional if the chlorine is held with the water first. I should have put a disclaimer - those Chem classes and labs were a looonnng time ago. I'm sure I'm not thinking about this correctly. And probably talking you in circles.
If there's a thread somewhere explaining all this, point me in the right direction. Or maybe I missed it in pool school. I'm going to wander back over there now that I have it clear in my head what I'm asking/thinking.
Also, I assume that the FC tests count even the chlorine that is held by the CYA? So if it still tests as FC, why is it not effective as FC (back to why the level has to be so high with high CYA).
Sheesh. Good luck to anyone who can make sense of that mini discussion with myself.
Either way - higher CYA is recommended for SWCG pools...but lower FC. Can someone explain why you want to have the ability to hold more chlorine (high CYA) yet produce/maintain less chlorine with a SWCG than a non-SWCG pool with an even lower CYA?
All this has been bugging me.