1st test results - CYA down to ZERO?

[bhelme]

OK, so really it is my second full test, but I thought the 51 degree H2O might have affected things. Here are my numbers:
FC 1
CC 0
TC .5
pH 7.6
Alk 110
Cal 360
Cya 0
Temp 67

30K gal., IG plaster, 2nd season. SWG.
Since I haven't been able to keep my chlorine up any higher, I'm guessing that the Cya number must be right, but it was at around 35 all last year. Could it go to zero? All the other numbers are consistent with my "real" first test this year and my numbers from last year.

Any suggestions?

[duraleigh]

Hi, Brian,

Yeah, that's a pretty easy one. My CYA has disappeared the last 2 seasons as well. Some folks dont have that problem (the "chosen ones", no doubt ) but it looks like you and I are stuck.

Solution is easy as well....add the CYA per your SWG's recommendations. It'll probably be somewhere around 60-80ppm.

Dave S.

Two other thoughts:

I don't think temp will significantly affect your tests...could be wrong..anybody have any thoughts?

Secondly, TC is the addition of FC and TC. So if FC = 1 and CC = 0, then TC is always the total of those two....1

[bhelme]

Yeah, I know FC+CC=TC,I prolly shoulda changed it to agree but I left it the way the tests came out. The drops and the color scale aren't always easy to read - especially at that low level! CC really was 0 so that's the important thing there!

Thanks for the affirmation.

[waterbear]

I don't think temp will significantly affect your tests...could be wrong..anybody have any thoughts?

Low temerpature can slow or inhibit the precipitation of the melamine in the CYA test. It would be best to allow the sample of water to come to normal room temperature indoors before doing it if the outside temp is cold. It would also be a good idea to let the test bottle sit for a few mintues and then shaking again before transfering to the measurment tube (with the black dot on the bottom) to insure a more accurate reading.

[PoolDoc]

WARNING: This post is rated "CN", and is for Chemistry Nerds only!

Low temerpature can slow or inhibit the precipitation of the melamine in the CYA test. It would be best to allow the sample of water to come to normal room temperature indoors before doing it if the outside temp is cold. It would also be a good idea to let the test bottle sit for a few mintues and then shaking again before transfering to the measurment tube (with the black dot on the bottom) to insure a more accurate reading.

Evan, while that may be true, it's very, very common for pools to be opened to ZERO CYA, even when they were closed to high levels. I'd noticed this for years, before I understood the cause, which is biodegradation of CYA. I stumbled across the cause while investigating simazine, which used to be used as an algecide. It turns out that the biodegradation of simazine involves common soil bacteria. As it happens, these bacteria usually happen to be present in pool biofilms. And, it further turned out that CYA is an intermediate of this process.

So while no one started out to study the biodegradation of CYA, it happened that they did so, along the way of numerous University and EPA funded studies of pesticide breakdown. I usually try to avoid going too far in explaining this stuff, but with your college chemistry background it should be a breeze.

Information about this is much more common now, than it was when I stumbled across it. But, it still hasn't penetrated into the pool industry.

Here are some links:

http://www.pubmedcentral.gov/article...i?artid=106326
http://en.wikipedia.org/wiki/Atrazine
http://umbbd.ahc.umn.edu/cya/cya_map.html

To quote from the last link,
"Cyanuric acid is widely used in swimming pools and is generated as a metabolic intermediate during the bacterial metabolism of s-triazine pesticides. (Karnes, 1999). It is further metabolized by bacteria and fungi via hydrolytic enzymes that ultimately release the nitrogen as ammonia. For twenty five years, it was thought that cyanuric acid metabolism proceeded through urea as an intermediate. More recent studies (Cheng et al., 2005) have shown that urea is derived from spontaneous decarboxylation of allophanate during purification of metabolites. Thus, cyanuric acid metabolism to 3 mol of ammonia is now shown to proceed exclusively via biuret and allophanate."

Please note the bit about urea and ammonia -- it's this part that's so very relevant to the spring time problem some have of adding chlorine in huge quantities, but never getting a residual: they are trying to oxidize all that ammonia!

As a concomitant, they will often note that all the algae is dead, and the pool is very clear. This happens if the pool pH happens to remain at a high (7.8+) pH level. In that case, much of the ammonia is oxidized to monochloramine, which is more effective against many forms of algae and especially, biofilms, than free chlorine. (The whole Yellow OUT process is based on monochloramine creation.)

On the other hand, if their pH is low (7.2 or less) they'll tend to form dichloramine and nitrogen trichloride, neither of which are good for much anything, but are both very 'stinky' with what most people think of as a chlorine odor.

You can investigate this further by using the following term groups:

"cyanuric acid atrazine pathway" or
"cyanuric acid atrazine biodegradation"

Ben

[waterbear]

Ben,
I remember you stating before the board crashed that CYA CAN biodegrade! After reading through the links I wonder if it might be a good idea to test for ammonia and/or nitrogen compounds in a newly opened pool with no CYA to see if this can predict the possible high chorine demand? (realize this is just something off the top of my head There are a few easy tests for ammonia but there are some interactions that can give inaccurate results. Not sure if testing for nitrite and nitrate would be useful but if there are any areas in the pool where denitrifing bacteria might live in a closed pool with no sanitizer it is possible that it might give us an indicator.) Might be an interesting bit of research that could possibly provide us with another testing weapon to determine just what is going on in the water.

I want to STRESS that this is just conjecture on my part (and I am no expert--just a guy with enough knowlege to be dangerous so I am not suggesting that anyone try this!) but I would love to hear your thoughts on this.
I am going to google the search terms you suggested this weekend when I can devote some time to it and see what I can learn. Thanks!

[PoolDoc]

You *could* test for ammonia and/or nitrate . . . but I don't see the point.

The solution is the same, regardless: if you add chlorine in the late PM, and it's gone by the early AM, then you need to add a lot more chlorine that same PM, regardless of whether the 'goo' as CYA leftovers, PHMB leftovers, or algae.

In other words, since the test isn't going to change* what you do, why bother?

Ben

*There is a bit of an exception. If it's ammonia or urea, keeping the pH high is best. But, if it's algae or Baquacil, low is probably better. However, the 'differential diagnosis' turns on the CYA level now, vs last fall. If it dropped a bunch, you should assume that the pH needs to be at the high end.

[bhelme]

Wasn't good at HS chem, never took it in college - my apologies in advance. Since my pool is just 1 year old, I've been told to keep my pH down.
But since my CYA was down to 0 and my pH was on the high end when I opened up the pool, my understanding is that what I should be doing at this point is to let my pH stay on the high end and keep adding bleach in the PM until I get things under control? I'm assuming I should also add CYA now as well.

Thanks for the input!

[aylad]

Don't worry about the discussion above between waterbear and Ben, they're making it sound a whole lot more complicated than it really is. Just keep it simple: Yes, you need to add some CYA, either in the skimmer or in a sock or stocking in front of your return, and remember not to retest or backwash for a week or so because it takes a long time to dissolve and show up. How much you need to add will depend on your SWG instructions. And yes, keep adding bleach until you get your chlorine under control. As far as pH goes, if you're between 7.0 and 8.0, you're basically okay--the general consensus is that the lower you are on that end of the scale, the more effective your chlorine will be.......but then again, my pool "likes" a high pH so I don't try to fight it.

Hope this helps!

Janet

[IceT1]

Question about CYA: Where does one get it and what are some product names? While waiting for a better test kit to arrive, my test strips indicate my cya is zero. Thks.