I officially began the BBB method last night and the first step was purchasing a TF-100 per this site. Because the CYA test only goes to 100 I essentially had to guess and scale the remaining amount to figure I had about 130 ppm. I realize this isn't the most accurate but it provided a starting point.
Last night I rented a sump and pumped out approximately 75% of my pool water which typically holds 9500 gallons.
I thought the CYA test was pretty cut and dry at first but now I see why the instructions said its relatively subjective. I've tested two times this morning while refilling / shocking my pool. The first measurement was about 85 ppm and the second was about 65 ppm. The later test was conducted outside with sun at my back per instructions that I read somewhere on the Internet. I felt relatively confident with this test. However, to confirm my results I wanted to seek a third opinion and I made the trek to a local Leslie's. They tested the water and said the CYA was 125 ppm! I realize the reason not to test at the pool store as they don't really look into depth at anything. For example, my chlorine is about 24 ppm right now but she said it was 5 ppm because that's all her test goes to. Is the CYA test really this subjective or prone to error?
I'm very frustrated and don't know where to go from here. I feel my last CYA test was likely the most accurate but I really can't say for certain because this is only my third time testing. Any advice would be greatly appreciated. Thanks in advance for your assistance! Tis site is great btw.