Cause of CYA Boost?

AlbertSteg

Gold Supporter
Jun 19, 2024
23
Cape Ann (MA)
Pool Size
28000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Guided by the wisdom of this group, I boosted my CYA and Chlorine levels beyond my local pool store recommendations, and things stabilized around 50-60 CYA and 7-11 FC for the latter month of summer. Was really impressed how my readings sort of quieted down, with much less need to add chemicals.

Today, after a week of neglect, everything still looks pretty good -- crystal clear water. But I[m curious to see that my CYA has floated up from 50 twelve days ago to 80 today. FC has also mounted to 14, so I'm dialing back the SWG to 10% from the usual 50% looking for it to mellow out.

My question is just a technical one -- what causes CYA to increase, independent of adding stabilizer? I last added stabilizer back on August 17, when it was sitting at around 40. I kind of envisioned stabilizer like suntan lotion -- something that you slater on to get to a protection level and expect to gradually decrease until you apply another coat.

I think all I need to do right now is get the FC down to the 10-11 range (and maybe boost salt a bit), but I'm interested in adding a little more understanding about how CYA levels can by affected by things other than time?
 

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CYA is only increased by adding CYA. CYA does not naturally occur in other products.

It is more likely a testing error given the way CYA is tested. I would test again in a few days.
 
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