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

sadohert

Silver Supporter
Oct 10, 2016
29
Waterloo, Ontario
TFP Friends - I think the key question I have here is whether my black dot has disappeared (see picture below)... I have other sub-questions I would love to hear feedback on.
20200729_083439_HDR.jpg

If that dot has disappeared, then I'd say my CYA is around 40, which I believe is too low and might explain how much chlorine I'm having to add daily.
If it hasn't disappeared, my CYA is even lower than 40, in which case I definitely need to add more 1️⃣

I can still see the dot, both in real life, and in that picture above.

MAYBe I should have considered the dot to have disappeared much earlier in the test, and my levels are TOO high now (this is what its starting to feel like with the increasing amount of chlorine I'm adding to maintain levels).

SOOO, "How much does that dot really disappear?"

Footnotes:
1️⃣ I'm having a hard time understanding that I can still be this low given how much pure CYA I have deliberately added this year, in addition to running trichlor pucks in my chlorinator. Two summers ago my levels seemed to go WAY too high (according to the pool store... I started using a proper test kit this season), and I had to drain 18inches of water to fix it. The only explanation I have for why they skyrocketed is that I stuffed a bunch of pucks left outside over winter from the previous season into the chlorinator and cranked it up to 2x/3x what I normally run it at (yes, I know this was a dumb move).... but I caught onto the high CYA level within a few weeks. I can't reconcile the things I did 2 seasons ago to get a really high CYA level, with the things I've done this season that results in a really low level. I would think I've done more to increase CYA this season than I did 2 years ago, but the results are inverted?!?! Could the answer be that I actually DIDn't have a CYA problem 2 years ago, and the pool store test results are really that off? 2 years ago I was also having to dump a lot of chlorine in to maintain levels, which corroborates the pool store claim. Or maybe the answer is that I am already too high, and I'm not interpreting the CYA test correctly.
2️⃣ I'm adding about 1.5L of 12% Bleach every day now (up to the last few weeks I seemed to get away with 1.2L and still have FC==1.2 twenty four hours later... 2 months ago I was only adding 0.9L). Maybe the rain, and splashing, etc. has actually diluted my CYA? Or maybe I'm too high? 🤬
3️⃣The Trichlor pucks don't seem to dissolve that quickly. **IF** my CYA is still. low, maybe I need to turn up the chlorinator? I'm running it around 2-4, which has been my "go to" range since getting the pool, but in the early days of caring for the pool it seemed like I added pucks much more frequently.
 

HermanTX

Well-known member
May 20, 2020
170
Katy TX
I don't try to scrutinize the dot visibility. I either see it on first glance or not. My first view of your picture was - no dot.
I pour liquid in the tube until the dot is barely visible and look at the reading. I then add more liquid to the next level, if I still see it, I will continue, if not, I use my earlier reading.
It like the old psychology games - if you stare at a dot long enough, everywhere you look after that you see a dot.
 
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Brett S

Well-known member
Mar 15, 2019
634
Orlando
CYA is definitely one of my least favorite tests. The recommendations I have seen are to do the reading in bright sunlight, but with your back to the sun and the sample tube held in the shadow of your body at your waist. You are definitely not supposed to stare at the tube and examine it for any small signs of a possible dot, but just glance down while the tube is at your waist and see if you see a dot at first glance.

I definitely vote no dot for the picture above.
 

jark87

Well-known member
Jun 5, 2011
117
Flower Mound, TX
CYA is the one test that I actually pay attention to when getting water tested at the pool store. Their test is usually very close to my own, so I trust it from that perspective, and it helps me validate my “guess” as to when that #*@*! dot disappeared!
 

sadohert

Silver Supporter
Oct 10, 2016
29
Waterloo, Ontario
Thanks for the helpful (and funny!) responses.... I *think* I can relax my "dot scrutiny" enough... more of a "glance" than a "stare".... if that's the case, maybe I'm way too high on CYA. Going to head to the pool store for some chems and a test...
 

sadohert

Silver Supporter
Oct 10, 2016
29
Waterloo, Ontario
UPDATE:

* Tested my FC level about 2 hours ago with my home kit and there was zero chlorine. This was after adding ~2x my normal amount 4.5 hours earlier (2.4L). This freaked me out big time, based on the replies above. The replies above made me worry I was actually very wrong about "the black dot" and CYA was much higher than I thought and no chance chlorine would stay in the pool.
* Took a water sample to the pool store assuming I was going to get a bad CYA reading, and would need to start to exchange for fresh water to reduce it.
* Pool store informed me CYA is at 29ppm, which is reasonably consistent with what my "black dot" interpretation has been telling me.
* Pool store said many people are having a hard time with the chlorine this year due to weather.
* PS recommended I "shock" once a week... but I've read on TFP this is not necessary if I'm keeping up with the chems.

My current theory on my issue is that I was not actually maintaining the 3ppm I should have. Instead of 3ppm being my minimum level the pool ever drops to, it was more a matter of "I'll add chlorine to get above that", but likely it spent a good portion of the day below that level.

I'm thinking I:
1) SLAM tonight in prep for OCLT
2) Run OCLT... see how much I drop overnight. If I drop more than 1ppm then continue the slam and OCLT until I see the overnight drop below 1ppm.

Does that make sense?
 

Enumjon

Active member
Apr 30, 2020
43
Tijeras, NM
Another thought from a newbie, not sure how the experts feel about this. In my limited experience pool clarity plays into the readings I get on the CYA test. I had been running about 50 on the CYA test all year. But then a week ago I got a reading of 60. About this same time I started to have algae, so did a slam. Once the slam was over my water was crystal clear, and the CYA test showed a 40. Since we are looking to see a black dot, slightly cloudy water gave me a higher CYA reading. Since you are starting a slam you may be in the same situation.
 

sadohert

Silver Supporter
Oct 10, 2016
29
Waterloo, Ontario
Another thought from a newbie, not sure how the experts feel about this. In my limited experience pool clarity plays into the readings I get on the CYA test. I had been running about 50 on the CYA test all year. But then a week ago I got a reading of 60. About this same time I started to have algae, so did a slam. Once the slam was over my water was crystal clear, and the CYA test showed a 40. Since we are looking to see a black dot, slightly cloudy water gave me a higher CYA reading. Since you are starting a slam you may be in the same situation.
Interesting.... I can see already cloudy water skewing the results... interesting to hear what the pros think too!
 

PoolingInKC

Member
May 20, 2016
20
Overland Park, KS
I agree that the visual test for CYA is a pain in the butt. I always saw the dang dot but then took the advice from here about "first glance." I still call CYA my least favorite test but......at least I don't stare at the vial anymore!!!
 

pb4uswim

Active member
Jul 23, 2020
35
Michigan
Struggling with this test too. I’m going to try the following tomorrow. Instead of watching as I fill up the tube, I’m going to fill it to the point of cloudy but for sure still there. Then I’m going to fill it to each mark (60, 50, 40, etc.) and just take a quick look at each mark one at a time. Hope that makes sense. Maybe I’ll get a better feel for the test doing that and be able to better distinguish when the dot disappears.
 

pb4uswim

Active member
Jul 23, 2020
35
Michigan
So I did the test today. Basically, I filled the tube to a certain point and then moved the tube down to my waist and looked to see if the dot was visible. This did indeed make the test easier for me. At 60, for sure could see the dot. Same at 50. At 40, it was pretty much gone. At 30, it was for sure gone. Given the test is a view "at a glance", I'm going with 40.

I also did the test twice. At 30, it there was enough solution left to dump out a bit, back down to 50 and try it again. Given this method and assuming no one informs me that I'm making a process error, I felt pretty good to round my CYA to 40. It may be a little less, but it's closer to 40 than 30.

I hope I'm not violating my sample because this seemed a lot better than trying to pour the liquid in the tube while looking for the dot to appear all in one step. It also allowed me to take my eye off the dot and come back to it for a first impression type of view which is hard to do while pouring at the same time.
 
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HermanTX

Well-known member
May 20, 2020
170
Katy TX
I think you gave a good process for others to follow. I read in another post that you can just dump the solution back in the squeeze bottle and do it again. I think continued consistency will improve all of us.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
5,030
Central California
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.
 
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