Last summer was my first summer at a new house that had a pool. The prior owner used chlorine pucks and the CYA was very high all summer, in the neighborhood of 95. Pool School says the typical way to reduce CYA is to drain and replace water. I got tired of that after replacing about 12 inches of water, so I just used lots of bleach as called for in the calculator and the pool was fine but the CYA stayed high all summer. So far no surprises. But this summer, I just opened the pool and it balanced very quickly and got very clean very fast, but my first test of CYA reads 35 or maybe 40. Is there an explanation for how the CYA went down over the winter? If relevant, I live in central Virginia.