I began using a Chlorinator dispenser last summer. (3 inch tabs) Pool is 57,000 gallons. I monitored CYA levels routinely thru the season and metered the dispenser back when I saw the CYA getting in the 40 ppm range. At the end of the season I closed the pool with all levels balanced. I opened the pool a month back and upon doing my initial tests I found the CYA level at 100 ppm or greater. I've been draining water in an attempt to lower the level. So far I've pumped out over 7,000 gallons and put in fresh water. I've only been able to get the level down to 60 ppm. How much more dilution is necessary for a proper level. But.... the big question is... "how did the CYA level increase through the winter?" I want to avoid this situation next year.