I lose CYA all the time

bk406

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Dec 3, 2009
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Central Massachusetts
Split off of this topic. This discussion diverged from the original topic, so was moved here. JasonLion

As i've posted before, i lose CYA all the time. Not as fast as chulaman, but its considerable. i've lost, as far as I can tell, close to 30 ppm this season. I've NEVER had my chlorine go even close to zero, nor have I ever measured any ammonia, nor have i had any combined chlorines that would indicate its presence. There is something, somewhere, somehow that causes the CYA to breakdown besides the conventional wisdom here. I've stopped worrying about it and just bought and added more. (although I would like to know where it goes).
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
Re: CYA rapidly goes to 0ppm

bk406 said:
nor have I ever measured any ammonia, nor have i had any combined chlorines that would indicate its presence
If the chlorine oxidation of CYA were somehow accelerated in your case, then you wouldn't notice any ammonia nor CC since on a daily basis it's quite slow and continual. What we don't know is why this known process seems to be so much faster in your own pool. 10 ppm CYA loss per month resulting in 25 ppm FC extra chlorine demand would be 0.8 ppm FC per day compared to a more "normal" 0.2 to perhaps 0.4 ppm FC per day extra due to this oxidation (most FC loss is from sunlight so this loss is lower than that so not usually noticeable).
 

bk406

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Dec 3, 2009
2,690
Central Massachusetts
Re: CYA rapidly goes to 0ppm

I dont watch the chlorine loss that close. As long as it stays in the range it needs to be in, i dont fret over it. i have no idea what my daily chlorine loss is exactly, but ballpark it's around 2.
 

dmanb2b

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Apr 4, 2009
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Re: CYA rapidly goes to 0ppm

Bk...it's definitely not water loss, right? I know it's obvious and your savy with pools, but even the best forget about an autofill device. Anyways...just checking :goodjob:
 

bk406

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Dec 3, 2009
2,690
Central Massachusetts
Re: CYA rapidly goes to 0ppm

No autofill. I lose very little water. It varies with the weather, but on average i'd say I lose 1 inch every 10 days. Its not water loss. My salt concentration goes up with water loss, so I know it's all evaporation.
 

JUCA

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Aug 10, 2010
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Why not to consider the possibility of the presence of bacteria or algae into the filter? The sand area is more than one thousand the area of the pool. Why not to treat the sand of the filter with concentrated bleach (12% or 6% NaClO)?
 

chem geek

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If there were areas of channeling in the filter such that there was low enough water flow for bacteria to form biofilms and not get exposed to a lot of chlorine, then eventually that could cause increased chlorine demand as much of the chlorine would spend its time oxidizing outer layers of the biofilm that would continue to be regenerated. I suppose that the bacterial conversion of CYA into ammonia could occur as well, though that is speculative in this kind of scenario and we haven't seen that before.

Anyway, it doesn't hurt to check the sand filter, stir up its contents carefully, just to see if perhaps there is channeling or visible biofilm. I'm guessing you won't find anything.
 

duraleigh

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Apr 1, 2007
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Like bk406, I seem to lose a enough CYA over the course of a swim season that splashout alone does not account for all of it. Also like bk406, I simply ignore it and accept that some is going to need replacement.

This summer, I will try to be more diligent about testing for CYA to see if I can be more specific.
 

dschlic1

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Oct 5, 2007
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Valrico, FL
I am of the opinion that there exists a biological process to degrade CYA without producing ammonia. I believe that there is a water borne mold that can and will consume CYA. In addition it appears to be resistant to chlorine. Just my opinion.
 

Beez

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May 19, 2009
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Dallas, TX
duraleigh said:
Like bk406, I seem to lose a enough CYA over the course of a swim season that splashout alone does not account for all of it. Also like bk406, I simply ignore it and accept that some is going to need replacement.

This summer, I will try to be more diligent about testing for CYA to see if I can be more specific.
Count me in as well. I started this past summer with CYA at 60, give or take, and it dropped down to 20 by the end of the season with negligible water replacement. Even taking testing error into consideration, that's a significant loss.

The ironic part is that the previous season I had to work so hard to bring my CYA down, that I was accustomed to thinking of it as almost immovable.
 

chem geek

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When there is chlorine in the water, I'm more inclined to think that there are catalysts to the chlorine oxidation of CYA so that it just gets sped up. A drop in CYA of 10 ppm per month would consume 30 ppm FC per month of chlorine which is only 1 ppm FC per day so could well be hidden in the daily FC usage, especially if it's typically 2.5-3 ppm FC per day. One would not measure any ammonia or monochloramine in this situation since this oxidation occurs continuously at a low rate. Also don't forget that summer rain overflow can dilute the water so account for at least some of the drop.
 

PoolGuyNJ

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May 20, 2007
3,192
South Central NJ
During the course of another thread on another board I frequent came a discussion involving a poster's CYA level where someone quoted the following link as evidence of CYA loss that is quite contrary to how I, and thousands of others, have seen it behave in a pool. I am not Chemist but neither am I a completely ignorant oaf but this is beyond me and my understanding.

http://umbbd.msi.umn.edu/cya/cya_map.html

It seems to me that this is more than the "life cycle" of CYA in a pool.

Scott
 

chem geek

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I have referred to that specific pathway before in the thread Degradation of Cyanuric Acid (CYA), but this pathway is invoked by bacteria that have specific enzymes described in that pathway to accelerate such degradation. It does not normally occur without such bacteria just as our bodies (and most organic compounds) do not decompose (get oxidized) in air spontaneously even though it is thermodynamically favorable. In that same thread I also discuss the chlorine oxidation of CYA which is much more likely because in a properly sanitized pool there will be no living bacteria to degrade CYA. We have seen such bacterial degradation of CYA in pools that had the chlorine get to zero and I describe my own personal experience with this phenomenom in this thread and we've seen this in other pools upon spring opening when such pools are "let go" over the winter.

Now that doesn't mean that there can't be some sort of catalyst that accelerates CYA degradation through either path though more likely the chlorine oxidation path, but we haven't identified what it is, if there is one.
 

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