I've been trying to bring my CYA down from 100 early last summer. I had a bottle of CYA reagent from the fall that I tested with, it was showing CYA at ~50 after I did a partial drain and refill and LOTS of rain. I used this number to SLAM about 3 weeks ago. I complete the SLAM, passed the over-night with .5 ppm loss 2 nights in a row. Chlorine levels came down rapidly during the day from the SLAM. Bought a new Taylor K-2006 since mine was 2 years old and tested CYA with that...can still see the black dot at the 30 mark. Tested again with the older bottle, still showing between 40-50. Waited a couple weeks and retested with the newer bottles and still less than 30. I'm losing 3-4 ppm chlorine easy during the day, adding at least a gallon of bleach every night. I'm hesitant to add CYA after working to lower it and not sure what test result I should believe. Water is crystal clear and I lost 1 ppm overnight last night but I tested 1.5 hrs after the sun came up. The pool gets full sun pretty much all day. Wondering if I should I add some stabilizer at this point?
CYA 50 or 30??