A few weeks ago, I tried testing my CYA but found I didn't have enough reagents to do the test. No problem. I ordered a refill and took a sample of water to the pool store in the meantime. I suspected my CYA was low since I had replaced so much of my water since last Summer and I was having trouble keeping my FC up. Sure enough, the pool store's test tells me my CYA was about 30. I bought enough CYA to bring it back up to 60 or so and I added it to my pool.
Now, it's been a few weeks and I'm pretty confident all the CYA granules have been absorbed. Also, my refill arrived quickly after I ordered it (thanks, duraleigh!) so I did a test. Result? CYA = 30. I know it's a subjective test and all, but what the heck? Was it zero when I had the pool store test it? If not, how did I see no increase?