As I am in Florida, I pretty much maintain pool all year round. I did slack off a bit during winter (DEc and Jan) , but always maintained FC at 6ppm and PH at 7.5 .
Anyway, in March I did full test and found CYA was at zero (I guess due to lots of rain over the previous 6 months)
I raised it back up to 75 and all was well.
I have noticed FC has dropped over the last 5 weeks from a steady 7 to now 4. I initially thought is was just because way more sun was getting on the pool as the summer draws in, so increased SWG to 65% and increased pump run from 6 to 8 hours.
I just tested and FC is at 4, so it is not holding. So I decided to check CYA again and it is at 30. We have had a couple of big storms since March and also, it has been mainly super hot and dry so I am filling the pool about 4 inches per week, because of evaporation, but can you tell me what else may cause a 40ppm CYA drop in 3 months , and what tests I can do to figure out what is going on. OR is this just normal, based on the rain and the large amounts of pool refills. thx.
Off to Leslie's pool store now to go buy the 172oz of liquid stabilizer the pool math table says I need....... It gets very expensive maintaining CYA lol