CYA test help

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CurtisT

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Jul 2, 2009
59
My CYA tests have been reliably measuring around 50 all summer. Today I tested it and the dot is gone even prior to hitting the 100 mark. I haven't added anything but bleach and acid since the last test so I know my level isn't that high. I'm wondering now that the water temp is down in the mid 50's if the temperature affects the results of this test? Is that possible?

On another note (and possibly related). I'm noticing some calcium buildup on the inside of the test tube. Is there a good way to clean that out? Would a few drops of muriatic acid in 10ml of water do the trick?

Other measurements:

FC - 4
pH - 7.6
TA - 70
ch - 310
Bot - 30
 
I assume you are using R-0013 to test for CYA. Taylor lists no interferences with that test but I seem to recall someone mentioning to let the sample warm to room temp and then test. I have never tested the water that cold.

Acid will do a great job of cleaning up your view tube. I would dilute it 3:1.

I'm not sure I have ever seen a report of build-up on the view tube. Are you rinsing fairly well?
 
Yes, temperature affects the reading; it certainly matches my experience. My CYA went up as the water warmed, despite not adding any. I believe it's the reaction rate of the reagent with the CYA, as chemical reactions speed up at higher temperatures.

I've been known to do my pH and FC as soon as possible after drawing the sample, then mix up the CYA test with the speedstir and set it aside, in the sun. Then do the rest of the tests (and CH takes me a while, even with speedstir) and return the CYA test to the speedstir again for another full mix cycle before I start taking readings.

Thorough mixing really makes a difference on all the count-the-drops tests.
 
That last post doesn't correlate with Richard320's issue where the temp has gone down.

I'm having a similar concern as Bruce, Sal and I couldn't get a consistent reading this weekend with water temps at mid 50s. If CYA will go up with temp then I'm in trouble as we measured at approx 70 (varied as low as 50 and as high as 80) - this after approx 16 hours of RO treatment and an original CYA of over 200 (hence the puripool treatment)
 
The CYA test usually works even when the water is cold. However, sometimes it will read low when the water is cold. Warming the sample up to room temperature before testing avoids any possible problems. The CYA test will read high if read in artificial light or heavy cloud cover. Ideally it should be read in indirect sunlight (or using a sunlight simulator).

Even under ideal conditions, the CYA test is somewhat subjective. Different people are likely to get somewhat different results. I call the CYA test +-15. Even though you can train yourself to be more precise than that, especially by practicing with a known calibrated test sample, few people are consistently better than +-15.
 
Got this from a LaMotte article (can't seem to find the link now :oops: ). I take it as saying colder water gives higher CYA readings than what it really is:

"Water temperature is a source of error when testing cyanuric acid in pools. This primarily occurs with the turbidimetric tests. A 20° F increase in temperature from normal testing temperature can result in a 10-20% decrease in the CYA readings. A 20° F drop in temperature can result in a 10-20% increase in the CYA reading. So if a water test sample reads 50 ppm CYA at 75° F, this same sample could read 60 ppm at 55° F. Conversely, this water sample could read 40 ppm at 95° F. It is a see-saw effect, as one goes up the other goes down. Table 1 gives an example of test results for both photometric and visual determinations of CYA as a function of temperature. So in early spring or late summer when water temperature can reach extremes the influence of temperature on the test result should be considered. Follow manufacturer’s recommendations for the ideal temperature range for the CYA test."

In this example, they used 75 degrees as the most "accurate" temp for CYA measurement. Any thoughts?
 
This assumes that one is operating at a pH where there is an equilibrium between precipitated melamine-cyanurate vs. separate melamine and cyanuric acid. Maybe LaMotte was trying to do the CYA test at normal pool pH, but the solubility of melamine-cyanurate at normal pH is around 20 ppm meaning that you wouldn't even see any precipitate until the CYA got high enough.

The Taylor test uses a buffered system at low enough pH to force more melamine-cyanurate complex to form so there shouldn't be very much temperature dependence in terms of an absolute reading. What can happen, though, is what people have described of lower temps causing slower reactions so that you need to wait longer before taking a reading if you want it to be accurate -- 30 seconds of mixing may not be enough at colder temps.
 

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It seemed as if I could see a "cloud" in the mixture as I put the solution into the CYA vial, Richard. I had never seen that before, and it seemed odd to me. We ran the R/O system for 13 hours on this pool (CYA was 200+; guessing, of course) but CH was only 330 and TDS about 2,500. Typical pool with these stats would run 8 hours or so to clean. We ended up shutting down at 500 TDS and 180 CH (IIRC), but I was not seeing a CYA drop like I had expected. The weird cloud just caught my eye and seemed out of place, which is why I started looking for anomalies.
 
simicrintz said:
It seemed as if I could see a "cloud" in the mixture as I put the solution into the CYA vial, Richard.
Click to expand...
That sounds more like some sort of interference with something in the pool water reacting with something in the melamine solution (other than CYA, which takes longer to react as you've normally seen). I don't know what that is.
 
It was really cold that morning - both water temp and ambient air. I'm on the road this week but on Saturday I will grab a sample and bring it inside and let it get to room temp (approx 70 degrees) and then post what I measure the CYA at.

As Bruce and Sal posted above, the water was ridiculosuly clean. That's why the CYA measurements don't make sense. FYI - I couldn't see a single floater in the water that night - it was that clean! :goodjob:
 
There is one other possibility, though I am not sure you can ever figure out if it happened or not. Many people claim that CYA can crystalize in the pipes (or elsewhere) and then redissolve when the CYA level goes down. This is nearly impossible to prove, so I can't say for sure that it really happens, but many people have reported CYA levels failing to drop as much as expected (which is where this theory comes from). The alternative explanation, which again could apply here, is that the CYA level was far far higher to start with than you thought it was. You need to test at high dilution to distinguish 200 from 1,000, and high dilution introduces other errors.
 
JasonLion said:
There is one other possibility, though I am not sure you can ever figure out if it happened or not. Many people claim that CYA can crystalize in the pipes (or elsewhere) and then redissolve when the CYA level goes down. This is nearly impossible to prove, so I can't say for sure that it really happens, but many people have reported CYA levels failing to drop as much as expected (which is where this theory comes from). The alternative explanation, which again could apply here, is that the CYA level was far far higher to start with than you thought it was. You need to test at high dilution to distinguish 200 from 1,000, and high dilution introduces other errors.
Click to expand...

Jason, if this is true, then in theory, Jose's CYA could still continue to climb as it loses its crystal form. Does CYA react differently with pool surfaces (vinyl or plaster)?
 
We don't run the pool filtration while we do our process, so if there was crystallized material in the pipes I would assume that it would take flow to release it. The pool water had not yet "blended", as we were checking with the pool still. It may rise if this possibility exists now that Jose is running the pump, but we saw the this occurrence prior to running the pool pump. Weird.
 
simicrintz said:
The pool water had not yet "blended", as we were checking with the pool still. It may rise if this possibility exists now that Jose is running the pump, but we saw the this occurrence prior to running the pool pump. Weird.
Click to expand...
That really is weird.

CYA doesn't react with or accumulate on vinyl. There are rumors of CYA interacting with or accumulating on plaster in rare cases, but I'm not sure if they are true or not.
 
Hello everybody - I'm back :)

So I measured this morning and everything was spot on as before. I measured the CYA at 60-70. Took a sample to the mom and pop pool shop that I'm buying chlorine and acid from and he measured it at 60 also. Given that the pool gets full sun exposure all day (even now in winter). I'm ok starting a bit higher. Next step is to raise the FC to 6 per the pool calculator.

Other measurements were: PH 7.4, FC was at 3, TA at 60.

Should I raise the TA or leave it alone?
 

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