First off, I want to say hello to all the old friends here. Miss you guys!!
I haven't been around for a while, but I thought this might add to the vanishing CYA body of knowledge.
- Taylor K-2006 Test Kit (with refills from tftestkits)[/*:m:3lir1zkd]
- I last measured CYA when I opened the pool on March 9th: 60ppm[/*:m:3lir1zkd]
- Since then I have kept FC at a constant 5-6ppm with my SWCG and manage pH bi-weekly to 7.8 to 8.0.[/*:m:3lir1zkd]
- I had a cheapo blue 8mil solar cover that was always on when the pool wasn't in use[/*:m:3lir1zkd]
- Pool temps up to 92 degrees[/*:m:3lir1zkd]
- No splash out[/*:m:3lir1zkd]
- No leak (Before I got the cover I thought I had a leak because I was losing so much water. It turned out this this was primarily due to evaporation. Once I got the cover, water loss was reduced to ~0.5" per week. I continue to maintain meticulous water loss records out of habit.)[/*:m:3lir1zkd]
- After two years the cover was starting to fall apart, so I replaced it with this 16mil Clear cover.[/*:m:3lir1zkd]
- Two days later when next I measured FC it was at zero. I bumped up the SWCG to compensate, but I couldn't get it to hold. I could only attribute this sudden loss of FC to the clear cover, which I surmised must be letting UV though.[/*:m:3lir1zkd]
- I was debating abandoning the clear cover getting a new blue cover, but in the meantime I decided to bump up the CYA to compensate.[/*:m:3lir1zkd]
- I measured CYA to determine how much to add, and it was zero.[/*:m:3lir1zkd]
- Double checked the reagent with a 50ppm CYA standard and the reagent is fine.[/*:m:3lir1zkd]
So this is definitely not the over the winter version, the ammonia version, or the slow but steady (5ppm/month) version of CYA loss.
All I can think of is that CYA it loss is accelerated above 90 degrees.