Please bear with me as this is my first post. I am a new pool owner (Missouri) : 35,000 gal inground, vinyl pool with sand filter. Regular use of Trichlor tabs with frequent Dichlor shocking was recommended by other pool owners and the pool store pros. This is common practice here with little regard for CYA levels. After opening and initially cleaning the pool May 19, the CYA level was 26 (pool store reading). By June 20, CYA was 59. I use a Taylor K-2006 kit. By July 4 it was 72. I terminated shocking with Dichlor. On August 7, CYA rose to 95 and I terminated adding any more Trichlor and switched to daily use of bleach keeping free chlorine levels between 2-3 (half to one gallon daily). In the 3-week period between August 7-28, rains have keep the pool level about normal with little splashout and two backwashes. I anticipated the CYA level on August 28 to be 95 or maybe a little lower, but it rose to 120. I'm wondering if the test kit or the tester failed although I tested twice. Being new to pool management, I wasn't even aware of the FC to CYA relationship until well after dosing with Trichlor and Dichlor. I plan to continue with bleach the remainder of this season, but I don't feel comfortable with heavy doses to maintain around 10% the CYA level. The pool water has looked crystal clear all season. Weekday use has only been a couple people, while maybe up to 10 swimmers on the weekends. Our season is almost over and I will need to drain some water at closing and probably a few times before opening again next May depending on snow and rainfall. I anticipate using bleach next year to avoid adding any more CYA unless it's needed. Here are the current water values: FC-2.5, CC-0, pH-7.8, TA-105, CH-100, CYA-120. Any ideas why CYA continues to rise would be appreciated and whether I can get by this year without a major exchange of water until I can reevaluate next spring. Thanks!