how to read CYA accurately?

It is a very subjective test. What helped me the most was ordering the solution that has a known CYA of 50 (tftestkits.net) and practicing with it.

Be sure you are doing the test outside on sunny day, with your back against the sun. Vial held in front of you at waist level holding vial with 2 fingers. Go slow, and when you get a reading dump it back in the squeeze bottle and re-test. You can do that a few times until you are confident of your result
 
Having the same problem. Using pool math I should have a CYA ~37. Tested with the 2006 kit and the black dot never disappears all the way to the top. It's almost gone but always there.

Before dumping more CYA I ordered the 50 CYA solution. Same thing, the black dot never disappears all the way to the top. Maybe I'm just really perceptive? :D

Bought this kit last year, the R-0013 says expiration in 2017. Kept in a cool, dark cabinet under the sink. Should I just order new reagent just to be sure?
 
Should I just order new reagent just to be sure?

The CYA test is one of the most stable, it's good for along time past the expiration unless it was just a bad batch to begin with. I would say highly unlikely but only way to know for sure is order some more R-0013 or the 50 ppm test sample. If you are going to go that far I would order both and cover all the bases.
 
The CYA test is one of the most stable, it's good for along time past the expiration unless it was just a bad batch to begin with. I would say highly unlikely but only way to know for sure is order some more R-0013 or the 50 ppm test sample. If you are going to go that far I would order both and cover all the bases.

Just checked tftestkits and the 50ppm standard solution is no longer there. Well, ordering some new R-0013 since I've reran the tests several times and still the black dot never disappears.
 
I can tell it is definitely visible below 60 and definitely invisible above 40ppm- it is a big range though.
That's within the margin of error. CYA is very crucial to the type of chlorination we teach.

However, the PRECISE amount of CYA is not necessary to know. With 11 years practice, I can get it pretty close. Patience, Grasshopper!

Seriously, if it looks somewhere between 40 and 60 call it 50 and walk away. No harm will come to your pool.

The R-0013 reagent is melamine....pretty stable stuff. I would believe what it is telling me.
 
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