CYA Test Confusion

Tjcervenka

Member
Apr 14, 2020
13
Illinois
I’ve tested via liquid my CYA and have never seen anything below 100. I so wish there was a more definitive test like counting drops. I’ve also tested using two different strips and they both come back 50. I tested the strips with tap water and they correctly showed “0”.
Which should I trust? Makes a huge difference in my FC target range. Thanks for your thoughts.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,932
San Dimas, CA (LA County)
The turbidity test is unfortunately the best.

Try this: mix up the sample, then pour it in the view tube to the 100 line. Then go stand on the patio in full sunlight and hold the view tube just at the very top with thumb and forefinger at waist height and look down. Do you see a dot? If you do, then [pour the sample back into the mixing bottle, swirl it a bit and then fill the view tube to 90 and try again. Repeat until the dot disappears. There's no shame in pouring it back and forth to be sure of what you're seeing. Bright lighting is essential. I get a different reading if I hold the tube normally, like a beer can, because my fingers block a lot of light.

And if it really bothers you, you can order a CYA standard solution and figure out what combination of light and distance has you read it correctly and then use the same technique with your pool sample.
 
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mguzzy

Gold Supporter
Jul 8, 2015
2,426
OV, CA
Welcome to the Forum!

@mknauss has a great suggestion. He fills the tube to the lines and reads it there. Since the test only has a resolution of 10, there is no point in trying to read 12.45646. It's either 10 or 20 or 30... so fill the tube to those graduations and check the dot from there.
 

Tjcervenka

Member
Apr 14, 2020
13
Illinois
The turbidity test is unfortunately the best.

Try this: mix up the sample, then pour it in the view tube to the 100 line. Then go stand on the patio in full sunlight and hold the view tube just at the very top with thumb and forefinger at waist height and look down. Do you see a dot? If you do, then [pour the sample back into the mixing bottle, swirl it a bit and then fill the view tube to 90 and try again. Repeat until the dot disappears. There's no shame in pouring it back and forth to be sure of what you're seeing. Bright lighting is essential. I get a different reading if I hold the tube normally, like a beer can, because my fingers block a lot of light.

And if it really bothers you, you can order a CYA standard solution and figure out what combination of light and distance has you read it correctly and then use the same technique with your pool sample.
Thanks. The standard solution may help give me piece of mind that I’m doing the test correctly.
 

Tjcervenka

Member
Apr 14, 2020
13
Illinois
Ok. Now I’m really messed up. I use the R-0013 CYA reagent on a 50ppm CYA Standard I purchased (R-7065). I could still see the dot at the 30 line but not at the 20 line. Held at my waist in bright sunlight. Now I don’t know what to make of any of my results. My pool reads over 100 and the 50 standard reads 20.
Any ideas?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,936
Laughlin, NV
That seems to be more variance than it should be.

Did you keep the mixed sample? Try the test over and over with the same sample. Want to be sure it is well mixed and has had time to develop the melamine solution.
 

Tjcervenka

Member
Apr 14, 2020
13
Illinois
Just to confirm

Be sure you are following the steps in that article. Also review the Notes.
Followed it precisely. When I turn my back to the sun, the dot is still visible at the 40 line but not at the 30 line. This improves the variance I guess. I just noticed the notes about using tap water and doubling so I can try that.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,936
Laughlin, NV
Do not do the dilute.

Not sure what to say. Be sure you are just glancing for the dot. If you stare down the tube, you will see it.
 

Tjcervenka

Member
Apr 14, 2020
13
Illinois
I appreciate your advise and help. Glancing does help as if I stare at it, I think my mind can add the dot. At the end of the day, I’ll assume my CYA is 100. My pool has looked amazing so I should leave well enough alone I guess.
 
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