CYA: Chemical OR Organic

[aylad]

Once CYA is in the water, it is reduced a little bit over the swim season by splashout, etc, but basically should stay the same over the summer. However, some people experience a lowering of CYA over the winter while the pool is closed (not all--Watermom usually loses some of hers, but I never do, even though my pool stays open during the winter, I don't change my routine much). Also, bad algae outbreaks have been known to completely break down CYA levels to zero. Personally, I'd chlorinate to shock level based on the CYA of 45 until you get a better number. Even if the CYA is lower, with a green pool, chlorine at the shock level for CYA 45 won't hurt.

Janet

[Tredge]

I have to add new CYA every year.
The winter eats my CYA.

Its a mystery. There are theories as to why it happens but its still unsolved.

[Watermom]

Me, too. Every year.