why NOT keep a high CYA ?

[chem geek]

This issue is currently under investigation. Some people have reported that they can use higher CYA levels and correspondingly higher FC levels (according to Ben's chart) and come out ahead with lower chlorine loss. Some experiments are being done at the TroubleFreePool.com forum (near the end of this thread) to sort this out. So we don't have a definitive answer yet. If it were easy to reduce CYA in the pool, then I'd just say to try it, but since it's easy to increase CYA but not to decrease it, this isn't a simple test for you to do (the experiment is being done in an attached spa to a pool that has a separate circulation option so changing chemical amounts is easy).

Prior to this investigation, the thought was that lower CYA levels were better since up to half the chlorine was lost in a day somewhat independent of CYA level. What we are finding out is that the protection from CYA does appear to be greater than expected and this is due to additional protection mechanisms not described in some charts the industry used.

Richard