CYA decresed

[zhenya]

My pool is salt so I was running my CYA at 70-80 range. Last couple of month my SWG is not working so I am manually chlorinating water. Doing a test last week I noticed that my CYA is at 30, which is withing range for a manually chlorinated pool, but I just realized that CYA should never go down unless you replace water (which I haven't)

Could CYA go down overtime by itself only with water evaporation and some splashes?

Thank you.

 

[Texas Splash]

CYA typically only goes down with water exchange, backwashing, or lots and lots of cannonballs. Primarily water exchange. It doesn't go down with evaporation either. This year, more than most others, there have been repeated reports of unexplained CYA reductions. Not sure if there have been some bad batches of stabilizer out there or what. Mine dropped a couple times as well for no reason. All we can do is monitor and add stabilizer as required. But it never should go down on its own.

 

[Agent99]

Well we know for sure it isn't due to rain although I wish it was!

But, yes, CYA can decrease over time due to oxidation and sunlight and well, here is a really in depth discussion about it: Degradation of Cyanuric Acid (CYA)

 

[Sparkle]

This year, more than most others, there have been repeated reports of unexplained CYA reductions. Not sure if there have been some bad batches of stabilizer out there or what.

How would a "bad batch of stabilizer" first register on a test and then suddenly disappear ? If anything was bad under the circumstances you describe, it would have to be the test.

 

[jblizzle]

I don't know Sparkle, but I think it happened to me too.

Mine was around 50ppm all winter, added CYA and measured it around my targeted 80ppm. One month later it was back to 50ppm. Confirmed the readings with multiple tests and the CYA standard solution.

No way we got that much rain to account for that much of a drop. Did not SLAM the pool to breakdown the CYA faster. Very bizarre.

 

[Sparkle]

Right, so you observed your CYA increase and subsequently drop. How could that possibly be caused by a bad batch of stabilizer, if the test works properly ? Is there more than one kind of CYA ?

 

[Texas Splash]

The various types of stabilizer on the market may contain different amounts of "inert" ingredients resulting in varied percentages of active CYA, but the CYA (cyanuric acid) in each should be the same. Regardless of the brand name used, those differences should not cause a drop in CYA later once you've reached your target. I track my tests on a spreadsheet during the season just so I don't lose track of some of my important readings or to diagnose unusual trends/events. After the initial spring torrential rains, there has been almost no rain here in South TX. Back in Apr/May, my starting CYA was about 30 so I used the HTH brand typically used. CYA increased to 60 - confirmed. About a month and a half later I observed unusual FC consumption and confirmed no organics from passing OCLT which prompted me to check CYA - down below 40. I added a little more HTH which increased for a couple weeks then dropped again. My wife and I compared readings just to make sure. Later I tried an Aqua Chem brand and that seemed to work fine and held my CYA where I needed for a couple months. About a week a go I decided to give the HTH brand another try when I wanted to take my CYA up another notch. So far it's been holding my CYA as well. I never had that happen before until this summer.

 

[YippeeSkippy]

I'd like to know how the OP tested the CYA?? Themselves with a reliable test kit or was it a pool store test??

 

[zhenya]

I am always testing using my own Taylor kit.

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