Interpreting my CYA Level - How much does that black dot really disappear?

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,546
Prosper, TX (DFW)
I think the CYA test is one that people tend to overthink. Give it your best quick glance and make a quick decision on if you can see it or not. Treat it like the sun... a quick glance if fine, but if you stare at it too long you are going to have issues.

Also keep in mind that you always round up. If you are struggling between 30 or 40, call it 40 and go on with your day. Even if you are wrong, and your CYA is really 30, there is nothing wrong with keeping FC at the target levels for 40.

Even if you are in a SLAM, the world is not going to end if you use the SLAM FC level for the next highest CYA level.
 
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Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
6,264
Central California
I think the CYA test is one that people tend to overthink. Give it your best quick glance and make a quick decision on if you can see it or not. Treat it like the sun... a quick glance if fine, but if you stare at it too long you are going to have issues.

Also keep in mind that you always round up. If you are struggling between 30 or 40, call it 40 and go on with your day. Even if you are wrong, and your CYA is really 30, there is nothing wrong with keeping FC at the target levels for 40.

Even if you are in a SLAM, the world is not going to end if you use the SLAM FC level for the next highest CYA level.
I'll go ya one step farther, though this somewhat contradicts TFP teachings (so heed at your own risk!). It's what I did to come to terms with that awful CYA test. I devised my own CYA testing procedure. I do it indoors under 100% reproducible conditions. I don't rely on the sun, or my waste size, as both can vary wildly!! I decided for myself what the dot should look like, and that's what I base my CYA additions on. Over time, I've learned how my interpretation of the CYA test dot and which associated number it indicates affects my pool's ability to hold FC. That's all that really matters, not so much if the number is 70 or 75 or 80. Every pool is different anyway, and the TFP numbers are considered only a guide. What works in your pool, and in this case for you when it comes to testing CYA, is what ultimately matters.
 
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Yev

Well-known member
Jul 29, 2014
537
Independence, KY
As others have said, buy the 50ppm standard, and I do that test at the start of every season to remind myself what 50ppm looks like, and what the dot looks like when it "disappears". If it has been more than 6 weeks ince I last did the test, I redo the 50ppm, just to relearn.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
6,264
Central California
As others have said, buy the 50ppm standard, and I do that test at the start of every season to remind myself what 50ppm looks like, and what the dot looks like when it "disappears". If it has been more than 6 weeks ince I last did the test, I redo the 50ppm, just to relearn.
Can you save the standard and reuse it over and over again? If so, any idea how many times (or years) that might work? That does seem like a good way to go for someone just learning the test and their pool.
 

Yev

Well-known member
Jul 29, 2014
537
Independence, KY
From TF Test Kits, here is what I use.

The test

The standard

With this hardware, you use half pool water, and half reagent. I believe the test uses 7ml of each part.

With the standard, you replace the pool water with standard, so you use 7ml of standard and 7ml of reagent for every test.

You get 2oz/60ml of standard, so if my memory is correct at 7ml per attempt, you get 8 attempts of the standard test.

hope this explains it. If not, let me know and I will use more words to explain.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
6,264
Central California
Oh, that explains it, thank you. I didn't know that you have to mix the standard. I wonder if you could save the mix and still have a reliable standard. No matter, even at <$1 a shot, it's still a good way to get good at CYA.
 

pb4uswim

Well-known member
Jul 23, 2020
70
Michigan
Regarding your "second test." Not quite sure if you were saying this, but you don't have to dump out the solution from the first test. You can pour it back in to the sample container and start over, as many times as you need to. I always do that, at least twice.
Yes, I was saying that. However, after reading posts after I said that, I realize you are correct. No need to dump out any of a previous test.
 

tomliv

Member
Jun 7, 2020
6
MA
From TF Test Kits, here is what I use.

The test

The standard

With this hardware, you use half pool water, and half reagent. I believe the test uses 7ml of each part.

With the standard, you replace the pool water with standard, so you use 7ml of standard and 7ml of reagent for every test.

You get 2oz/60ml of standard, so if my memory is correct at 7ml per attempt, you get 8 attempts of the standard test.

hope this explains it. If not, let me know and I will use more words to explain.
The CYA regent in the test kit is 8 oz which is enough for ~ 15 tests according to the Test Kits Compared article in Pool School.

As the standard is 2 oz, I would think that you would get less than 4 attempts using the standard (2/8 = 0.25; 0.25 x 15 = 3.75) if you use the tftestkits mixing vial.
 

CrystalRiver

Well-known member
Jun 19, 2020
235
Massachusetts
Oh, that explains it, thank you. I didn't know that you have to mix the standard. I wonder if you could save the mix and still have a reliable standard. No matter, even at <$1 a shot, it's still a good way to get good at CYA.
No, the test has to be read within two minutes to be valid, per Taylor. You can't keep it for days for reuse.
 
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goody222

Silver Supporter
Feb 6, 2018
152
Chesapeake, VA
One quick note about the standard solution, I tried using an old standard one I purchased (1 or 2 years old) a few days ago and I got about 30, not 50. I'm currently ordering a new solution. Worth the $10 incl shipping to calibrate yourself every season. Personally, I find that I DO have to make sure I absolutely can't see the dot to hit 50 - but its different for everyone. I also wiggle the tube as I'm looking to rule out any reflections/shadows and I get better accuracy if I stand outside on a sunny day in full shade (I think it reduces glare and therefore, squinting).
 

markayash

Gold Supporter
Mar 21, 2016
2,420
Marietta Ga
Can you save the standard and reuse it over and over again? If so, any idea how many times (or years) that might work? That does seem like a good way to go for someone just learning the test and their pool.
Yes in fact airBubbles in the water will impact your results. I always mix it and let it sit 10 minutes. The TF kits mentions letting it sit but Taylor doesn’t
 

markayash

Gold Supporter
Mar 21, 2016
2,420
Marietta Ga
I have done mine after a few minutes, poured it back in the bottle and tried about 10 minutes later and got the same results. Don't know for sure if it matters.
It does say give a gentle mix before testing after sitting.
 
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