About 1.5-2 months ago, I dropped my CYA to 70 from about 110. There were heavy rains for three days straight over here, and I tested my water yesterday, expecting to see a lower CYA, but no, my CYA is now 100. I am a little lost about how the CYA went up. Bad testing? The weather was cloudy, so did not test it in sunlight. But i dont think that is the case. My pool hasn't seen a chlorine tab in 4 months now. I only use bleach.