CYA testing

[yann]

Hi all

I'd like to get a better understanding of CYA and how it works.

When I first inherited my pool, pool store testing showed CYA 30 and staff told me not to worry about it for now since it was still winter here.

Soon enough I joined TFP and with the sun getting higher in the sky now, I proceeded with my own water testing and got a CYA reading way below 30 (indicator still quite visible with a full tube), could have been 0.

After adding enough CYA to get me to 60ish, I noticed a "film" at the surface of the pool, which I assumed was my newly introduced CYA.

Now to my question.
How well does CYA mix with water?
If it acts as a "sunscreen", is it by floating on the top layers of the pool?
If so, is it fair to assume CYA concentration is higher at the surface than the deepest layers?
And in that case, shouldn't we test CYA with a surface sample instead of the traditional elbow-deep sample?

Thanks

 

[JoyfulNoise]

How well does CYA mix with water?
If it acts as a "sunscreen", is it by floating on the top layers of the pool?
If so, is it fair to assume CYA concentration is higher at the surface than the deepest layers?
And in that case, shouldn't we test CYA with a surface sample instead of the traditional elbow-deep sample?
Thanks

CYA has low solubility in water which is why it takes a very long time to dissolve. You never want to just throw it in the pool or into the skimmer. You fill a knee-high sock or lady’s nylon with it and hang it in front of your return jet.

It does not concentrate in the surface. Like all chemicals it mixes uniformly throughout the entire volume. The sunscreen analogy is a bad one at best.

You test it like every other chemical - best to use a sample from the deep end about midway down. I constructed a PVC sampling tube for this purpose.

No idea what that oily film was you saw. Some kind of contamination.

 

[yann]

Thanks

I did add CYA as recommended and it took a few days to dissolve

Not sure what the film was, it's been gone for weeks. It just appeared when I put the CYA in the pool, and disappears roughly a week later.

 

[domct203]

Thanks

I did add CYA as recommended and it took a few days to dissolve

Not sure what the film was, it's been gone for weeks. It just appeared when I put the CYA in the pool, and disappears roughly a week later.

Which brand/type of CYA did you use?

 

[yann]

Hi Dom

Used Zodiac UV Blockout, white powder dosed at 99.6% Cyanuric Acid.
Put it in a sock and in the skimmer box, squeezing the sock once in a while.

Description says: Protects chlorine from ultra violet light. Creates a barrier that floats on the pool surface stopping the sun from "eating" the chlorine. A must in the summer months.

 

[JoyfulNoise]

Hi Dom

Used Zodiac UV Blockout, white powder dosed at 99.6% Cyanuric Acid.
Put it in a sock and in the skimmer box, squeezing the sock once in a while.

Description says: Protects chlorine from ultra violet light. Creates a barrier that floats on the pool surface stopping the sun from "eating" the chlorine. A must in the summer months.

WOW......ok. Don’t ever buy that junk again. They obviously put something in it that floats on the surface, like those liquid pool cover products, to get you to think that a thin layer of junk on the surface is protecting your chlorine.

CYA is an organic chemical (cyanuric acid) that dissolved in the volume of your pool water and reacts with chlorine to bind it and hold it in reserve. A small fraction of chlorine (about 5% or so) is left over to become the active chlorine components (hypochlorous acid and hypochlorite anion) that disinfect pathogens and oxidize bather waste. By holding the chlorine in reserve, it is protected from UV photolysis.

There is nothing about that chemistry that requires any surface layer to form. So they are adding a small amount of some other chemical to give your water that oil-sheen look and make you think it’s doing what it says on the package. Total horse pucky!!

Next time you need stabilizer (CYA) go online to Amazon Australia or whatever, and buy only a product that is 100% cyanuric acid. No additives or magic potions.

 

[yann]

This description is from the pool shop website, not from Zodiac
i didn't even notice it until I checked today.

At the pool shop they had Zodiac and their own brand, both dosed at 99.6% and at the same price so I picked Zodiac.

There was no mention on the label of a protective film.

this is their MSDS https://www.zodiac.com.au/Content/cms/products/pdf/2015-msds/X0051800_Zodiac%20UV%20Blockout.pdf

i like the "secret " ingredient....

 

[yann]

For future reference , what brand of Australian CYA is 100% CYA?
all I could find are 99.xx%, making me think they all have a "secret" ingredient like the Zodiac one I bought.