16x32 16,400 gal vinyl pool. CYA has been high because I used dichlor at my pool store's recommendation. On 8/23 their Alex system said CYA was 146; on 8/29 it said 151. When I took a sample yesterday, she told me that Alex can only test to 151, so she added water and tested manually and told me it was 330! I have not put anything except bleach and borax into the pool since 8/23. My chlorinator has always been set to 1;and I turned it off last night. I drained approx. 3 inches of water twice last week and added fresh. Is it possible for CYA to increase that much that fast, with only bleach and borax added to the pool?

I have drained another 2 inches of water today; but if the CYA really is 330, I don't think that's going to help.

How much water can I safely drain from my vinyl pool? It is going to be sunny all weekend and I don't want the liner to shrink.

Thanks!