Bought a house with a pool last year and started trying to figure out how to keep the chemicals balanced. Took water in for testing and everywhere in town told me that CYA levels were part of some witchcraft science and to never worry about it.
Started following this site and decided to get pool in shape for this summer. Every time I vacuumed, I set the valve to waste and replaced about a foot of water 10 times. Then over the last two weeks, I have drained the pool to 50% twice and refilled.
This morning, according to my TF100 kit, I am at 45 CYA. Super excited that I was able to get it under control despite the fact that I wasn't sure it was possible.
So if you have been wondering if you can get your high CYA levels under control, you can. Go for it.
Now if I can just get my Stenner pump here, I can set up on an automated bleach system and try to maintain. Also, an FYI, if you order your pump from Water Treatment Supply don't throw away your measuring cups. It has been 9 days, and I still have yet to get the pump.