When I do this test, the instructions for the Taylor 2006-K test kit say to add the cloudy solution to the tube until the black dot "just disappears" when viewing from the top. Does "just disappears" mean that the dot starts to become difficult to see, or that it stops being visible at all? There seems to be a 20 ppm range between the point at which it begins to become difficult to see the the dot, and the point at which you can't see the dot at all.
The CYA Test
- Thread starter tomvalois
- Start date
The endpoint is when the dot can no longer be seen, aka stops being visible at all. Just be mindful that when you stare at it, it can often reappear because our brains are magical things 
A 10 ppm deviation in the test is completely normal and won't materially affect your pool maintenance. One good practice is to pour the mixture back into the vial several times and take an average of your results. CYA is the only test that is very easily repeatable without using more reagents.
A 10 ppm deviation in the test is completely normal and won't materially affect your pool maintenance. One good practice is to pour the mixture back into the vial several times and take an average of your results. CYA is the only test that is very easily repeatable without using more reagents.
The endpoint is when the dot can no longer be seen, aka stops being visible at all. Just be mindful that when you stare at it, it can often reappear because our brains are magical things
A 10 ppm deviation in the test is completely normal and won't materially affect your pool maintenance. One good practice is to pour the mixture back into the vial several times and take an average of your results. CYA is the only test that is very easily repeatable without using more reagents.
Thank you.