I know this isn't supposed to happen ... but it did. I tested CYA today and it was lower than the last test. From 65 to 45ppm.
I started the summer (a new pool owner) with low CYA and lots of leftover chlorine pucks ... so I've been using them and watching my CYA slowly go up all summer. My goal was 45ppm. When I last tested it, whoa!, it was 65 so out came the pucks. Worried about that number, thinking it might be even higher, I tested again today.
Today's test (using the Taylor 2006 kit) showed 45. I didn't believe it, so I did the test again. Still 45. All my other levels are close to the last reading, we haven't done lots of splashing, and there doesn't appear to be a leak (although I will do the bucket test now).
My question: Could this be user error -- as in, my eyes aren't giving an accurate assessment of whether the black spot at the bottom disappears? Or is there variation in the test, or even in where I take my water sample from?