Australia: How "granular" is your CYA?

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@acKsw, I didn't have much time when I replied to your post. The BABES paper certainly is quite interesting. Have a read through the discussion between RGB, chem geek, and JasonLion, above quote of "Pool Chemistry" leads to the beginning of their discussion. Chem Geek actually gives a very thorough review with comments on RGB's two papers on Borates and BABES, unfortunately RGB never replied to that and didn't adopt any of Chem Geek's suggestions.

CYA seems to lead to FC protection at rates higher than expected by just accounting for FC bound with CYA. E.g. 4ppm FC @ 80ppm CYA leads to smaller absolute FC loss to UV than 2ppm FC @ 40ppm CYA. Chem Geek explains that with a shielding effect of the lower water depths.

I like to keep my CYA in the 70-80 range in summer. Towards mid/end of Feb, I don't top up with CYA anymore until it gets down to about 40 and maintain that level over winter until about October.
 
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mgtfp said:
Interesting. And do you then add the 1:2 slurry through the skimmer?
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The 1:2 slurry was just a chemistry pool nerd experiment.

Officially TFP recommends the sock method in the skimmer or hanging in front of a return. I would caution against powdered CYA in a sock hanging in front of a return. I could fall through and settle on the bottom creating a localised area of low pH. Powdered or granular cyanuric acid has a pH of ~4. If pump run times are extended for CYA dosing the SWCG output should be adjusted to account for the possible extra FC output.
 
I used the skimmer sock method but I walked away for the first 24 hours. Upon returning, 99% of it was still there but easily squished out in 5 minutes of swimming it around. Keep in mind with my 35k gallon pool, my ‘sock’ was the sleeve to a long sleeve T-shirt with half the jug of CYA inside it. If it was just an actual sock it would only take a minute to disperse after soaking a full day.
 
Like modern masking requirements, I use the double sock method. I have a sock that sits inside a second skimmer sock. That makes sure that anything that filters through is very fine or pretty much dissolved.

That placed in front of a return seems to work best for me. Squeezing it every now and then helps, and the warmer the water the faster it dissolves.
 
I use the skimmer. I did some testing on very cold water (in the fridge, not stirred) and it never dissolved. But on my BBQ benchtop, approx 12-15 degrees (55-60F) it was dissolved after a day or two with no stirring. So for me, I just add it in the skimmer and it will get caught and dissolve mostly in the filter and some in the skimmer basket.

Marty from here found CYA caked up in his filter months later, so the method is not for everyone. Sock in skimmer is best, and probably good risk reduction to remove it after pump shuts off if there's any still in the sock.

What I buy (from any supplier) all cakes up in sock when wetted. Massaging it loosens it up, and plenty squeezes out like foggy dust, so that's going to the filter either way. Getting it into the sock was an extra step, which was what motivated me to do some testing.
 
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CRAD_oz said:
Jet

Are there any issues with undissolved cya stuck on a cartridge filter over time? Or in any type of filter?
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Undissolved CYA caught in the plumbing can have two problems, CYA remaining undissolved and/or remaining undissolved and causing a partial or total blockage in the plumbing.

The question is the answer in that undissolved CYA in a cartridge can remain undissolved, you’ve wasted your time, money and haven’t increased the CYA level in the pool as intended. Cartridge surfaces are vertical, if small clumps of CYA hit the vertical filter surface they will slowly dissolve while flow remains constant but if the pump is shut off they can fall through to the bottom and remain there undissolved.

In comparison, the filtration surface of a sand filter is horizontal. If small clumps of CYA settle on the top of the sand layer they will remain there until dissolved wether the pump is on of off.

From PubChem the pH of a saturated solution of cyanuric acid is 4.8 which is less acidic than apple juice so there is little potential for immediate harm to equipment due to CYA’s acidic properties. There is however concern with CYA creating a local pH of 4.8 on a pool surface be it vinyl, fiber glass or plaster.

To alleviate these problems FTP recommends to put the desired dose of CYA in a sock, in the skimmer, with the pump running until it is dissolved. With a cartridge filter it would be advised to leave your pump for a while after all the CYA is dissolved from the sock in the skimmer.
 
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Well, it has to go through the skimmer basket, so the pieces are small, and of course the pump flow is substantial. It does dissolve over time, even if hardened into a lump, but yeh, I wouldn't want to put anything in the skimmer that could be capable of blocking the suction line, for sure.

The only issue I've heard of is from one of the experts here who runs several pools. After several months, he found undissolved CYA in his filter, I believe it was either cartridge or DE. mknauss (Marty) mentioned that in a thread where this was discussed.

That's why I did the test in my fridge, and indeed, the CYA in the bottom of two glasses (one fresh water, one pool water) did not dissolve even after a couple of weeks (my fridge is at 2C (36F). Exact same glasses and amount outside on my bench in the shade did dissolve fully at around 12-15C (55-60F) after two days. None of the glasses were stirred. Both sets were covered so wind causing turbulence in the glass wasn't a factor, just temperature.

But all that said, the recommended method is in a sock in the skimmer basket, or hanging in front of a return jet. If hanging in the pool and massaging it, watch out for undissolved CYA on the bottom of the pool under the sock. If you see any, brush it around right away which works fine, and you won't leave a mark on your finish or liner.
 
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needsajet said:
I use the skimmer. I did some testing on very cold water (in the fridge, not stirred) and it never dissolved. But on my BBQ benchtop, approx 12-15 degrees (55-60F) it was dissolved after a day or two with no stirring. So for me, I just add it in the skimmer and it will get caught and dissolve mostly in the filter and some in the skimmer basket.

Marty from here found CYA caked up in his filter months later, so the method is not for everyone. Sock in skimmer is best, and probably good risk reduction to remove it after pump shuts off if there's any still in the sock.

What I buy (from any supplier) all cakes up in sock when wetted. Massaging it loosens it up, and plenty squeezes out like foggy dust, so that's going to the filter either way. Getting it into the sock was an extra step, which was what motivated me to do some testing.
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I’m not sure I’m allowed to say this so here’s the disclaimer; this is only for Australian members using powdered CYA with sand filters.

I just add it to the skimmer too.

If I put it in a sock it would sit there as a lump in a sock. I have a sand filter and how i do it is only for sand filters and better than tipping it in the pool as indicated on the product label. I put my desired dose in a small bucket with about the 3-4 times the volume of fresh water until a slurry forms. This takes about an hour and can be prepared the day or even a week before. I then tip it in the skimmer with the pump on medium or high. I do this at the beginning of a normal pump run cycle and don’t need to mess with my FC output.
 
Thanks for the replys. I'll continue to use the sock in front of the return method. I normally start it in the morning on a weekend so I can monitor and squeeze the solution it's all gone.
 
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I find that double socking works best for me. I have a sock, that is inserted into an actual skimmer sock. Its like double masking. When squeezed I do see a white cloud that disperses but dont get any sediment on the floor beneath the sock.

I also just prefer to put it in front of the return.
 
CRAD_oz said:
Thanks for the replys. I'll continue to use the sock in front of the return method. I normally start it in the morning on a weekend so I can monitor and squeeze the solution it's all gone.
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That's what I do. Seems to work. I usually only add up to 10ppm worth at a time, distributed over two socks in front of each of my returns. Give it a good knead after it caked up, and after that it usually disappears in a few hours. Some brushing from time to time to make sure there is nothing settling on the pool floor.
 
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