Active member
Aug 1, 2019
West Virginia
Finding this to be the hardest part about testing chemicals with the tf100 kit. I have done the test over and over and am finding that what is considered obscured is pretty subjective. I took pics at 0, 45, 40, 35 and 30. Can someone tell me at which level the point is considered obscure for this test. I did not get the cheat sheet chemicals nor do I have time to wait on them. If someone experience could give me their input on these pictures l; I’d appreciate it. I also compared the picture to how it appears in real life and is accurate.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
I can see the edges of the circle at 45. Looks gone by 40. Don’t sweat over it. 10 CYA variance is not a big deal. Better high then low.


Gold Supporter
Jun 28, 2017
Fresno, CA
I see a lighted background in the 0, 45 and 40 pics and it makes the dot stand out.
Shaded background in the 30 and 35 pics and no dot, nice and confusing. :scratch:


Bronze Supporter
Dec 24, 2018
Columbus, OH
I have this same issue. I got LASIK last year and have super sharp 20/20 vision now so it’s very hard for me to determine when the black dot “cannot be seen”. I have my husband do it for me lol. But to answer your question, I would go with 40. It is definitely in acceptable range for CYA. I have the same testing kit and besides the TA test, this one is the second most frustrating!


Bronze Supporter
Dec 13, 2018
Orlando, FL
I am confused. Why is it more obscured at 30 than at 45? I use the Taylor K-2005 kit. Is the TFP kit CYA test different?

P.S. This test gives me the most trouble also. But I just round up now based on advice from TFP.


Bronze Supporter
Oct 2, 2016
albany, ga
I've read many posts on this subject and have seen the following mentioned several times. Pulled the trigger on it a few weeks back and I love it. The liquid stays stable (pour and mix once) and the dot is moved up and down on a slider until it disappears. Still not 'perfect' but a heck of a lot easier to read in my opinion and lets you check it over and over again quickly without pouring and re-pouring and waiting for the bubbles to dissolve... : Blue Devil Cyanuric Acid Test Kit for Swimming Pools, 4 oz. : Garden & Outdoor


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Sorry to be a cynic but this test produces more hand-wringing and anxiety than choosing a door on the Price is Right.

Do the test however you like, then pour it out of the view tube back into the mixing bottle and do it again. Do it one more time if you are so inclined and take the average of your three readings as your final CYA.

You will be within the margin of error 98% of the time. Really, you will.