I seem to have lost 20 ppm of CYA over the last 2 weeks, which does not make sense. I am using the Taylor 2006 test kit and when I tested 2 weeks ago, it said my CYA was 50. Last night I tested and it said my CYA is 30. We did have a lot of rain on 2 occasions after the initial test and I needed to drain some water, but I have not otherwise refilled. In addition, I have cleaned my filter once since then, which resulted in a bit more water loss, but again, I did not refill.
I am concerned that I am not testing right, although the test kit instructions and the visual guide I saw linked here made it seem pretty self-explanatory. All I know is that I could see that black dot for a long time when I was adding the solution to the tube last night.
As a side note, I do have test strips, which I had bought earlier this year and the CYA reading off of those would indicate something a bit north of 30-50 (I think). I find it very hard to interpret the CYA reading on the strips. And I know they are not as reliable. I was just using them as a bit of a check.
I am not sure if it matters, but I have been able to keep the pH within 7.2 to 7.6, and alkalinity between 100 and 110.