First, a little background:
I'm in my 2nd full season of owning a pool, and, until very recently, was not using BBB. To maintain a clear/clean pool, I was using pucks for chlorine, MA for lowering ph (never needed to raise), and Sodium Hydrogen Carbonate to increase TA (never needed to lower) and Powder Shock "Plus" (sodium dichloro-s-triazinetrione; supposedly shock+clarify+enhances filtration (whatever that means)+no ph increase).
Also, our pool came with a Frog mineral system which we've used , but , per builder recommendations, we only used the mineral pack, not the "bac-pac" (copper) or chlorine dispenser (whatever they call it). I know there are a lot of Frog haters here, but so far this has worked well for us, and "allowed" lower FC levels without problem (or we got lucky, so far anyway). Makes sense as essentially it's adding silver which is known to be effective. With this method, we've maintained FC at 1-4 with no algae and clear water. I do plan to drop use of the Frog next season however, as now I'm becoming TFP educated Besides, those mineral packs aren't cheap, nor easy to find.
So, my problem is CYA... I'm not quite sure why, but as the weather turned cold here my CYA levels shot up the last few weeks. I know they were already up (I now know because of the pucks) but it had been in the 60-80 range for several months. Now it's ~120. I don't really see the point in draining/replacing water to lower it when I'm about to lower it to close and fill with rain/snow over winter and top off in spring to open.
I'd like to close my pool this weekend, so I'd like to go ahead and shock. My concern is according to the tables I need to raise FC absurdly high (e.g. 40+). At those levels will it drop to an acceptable range anytime soon (e.g. this weekend) and/or does it matter if FC is sky high when you close it up. Since I'm still under the effects of the Frog, do I really need to raise it that high?? Am I better off wasting a lot of water draining / replacing it to lower CYA first?? Other ideas??
Note that I have a dark plaster bottom which we don't want to "bleach" as well, which leads me to a followup question - can I put that much bleach in w/o staining/lightening the plaster (pool calc says ~13-14 gallons!). Over two years, we can actually already note a "fan" like area in front of the returns where the plaster is slightly lighter, and although I can't say specifically what caused it, I would assume chlorine.
CYA: 120 (est. - out of range)
CSI = .02
Thanks for any advice!