BBB working great so far after Spring Baquacil conversion but I am a little concerned about getting accurate CYA readings. The test is so critical to proper treatment yet it is so subjective. Today I did my normal Saturday am readings and got an initial result of between 50-60. Last week I was at 40, which was exactly what I have been running. No added CYA and only a little evaporation so I was concerned with the big jump. I rinsed, resampled and re-tested, this time being very careful to hold the cylinder exactly waste level and in proper daylight. Result = 40 ppm. I am 5'6" tall with relatively poor vision (yes, I had my glasses on!). If I were 6'5" with eagle eyes, I expect that I might get a different reading. I will order the 50 ppm standard solution to "calibrate" my eyes.
My question: Is there a sophisticated lab test (e.g., turbidity meter, nephlometer, etc) to accurately measure CYA? If so, what is the relationship between the reading and CYA level?
What do the pool stores use and which national outlet actually does this test? I realize it is difficult to trust the "kids" running the tests in the stores, but if I knew the technology I might be able to access it at one of the labs where I work. (And besides, I am just curious - This is Chemistry 201, right?).
In the interest of complete disclosure my morning readings are: