Cyanuric acid - what can we do?

Causes and cures for cloudy swimming pool water.
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Cyanuric acid - what can we do?

Postby VeronicaK » Thu 09 Apr, 2009 06:27

Hi. We have just found out that we have cyanuric acid in our poolwater. We have talked to several people about it and when asked what we should do we got different answers. Some said that we have to empty the pool and refill it. However, we have a limited access to new water and wonder if there's any other way of solving this problem. A chemical way maybe?

It would be really appreciated if someone could help with this problem.

Thank you,

Veronica K


Cyanuric acid - what can we do?

Postby VeronicaK » Thu 09 Apr, 2009 06:31

I was linked to this page and I just realized that this topic might not lie in the area of Cloudy Pool Water, hehe. Anyone that know where this topic should be? Although, we do have cloudy water, but if that is due to the cyanuric acid I don't know.

Thanks again and I'm sorry for being confusing,

Veronica K
chem geek
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Cyanuric acid - what can we do?

Postby chem geek » Thu 09 Apr, 2009 09:22

You do want some Cyanuric Acid (CYA) in your pool since it protects chlorine from breakdown by the UV in sunlight and it also moderates chlorine's power so that it isn't too strong (reactive). However, if the CYA level gets too high, then the chlorine becomes too ineffective (unless you proportionately increase the FC level) and that can lead to algae growth which can first be seen as cloudy water.

Right now, though, you should add some unstabilized chlorine, preferably chlorinating liquid or 6% unscented bleach, and do so in large quantities to kill the algae before it gets any worse. Whatever you do, don't use 'shock' products that contain Dichlor or Trichlor as these will only increase the CYA level.

Have you had your water tested? What is the CYA level? Actually, posting a full set of water chemistry numbers would be helpful -- pH, Free Chlorine (FC), Combined Chlorine (CC), Total Alkalinity (TA), Calcium Hardness (CH), Cyanuric Acid (CYA) and water temperature.

CYA is reduced through dilution of the water. You may not need to completely drain the pool, depending on the actual CYA level. You may only need to dilute by half, for example, if your CYA is, say, 150 ppm. A CYA up to 80 ppm is tolerable and can be managed, though normally it's in the range of 30-50 ppm unless your pool gets a lot of direct sunlight for very long days.

There are some chemical products on the market that reduce CYA through precipitation, but they are hard to work with since you end up with a cloudy pool that takes a while to clear. Such products basically work the same way the CYA test in a test kit works. They add melamine and CYA combines with it to form a precipitate that then needs to be filtered out. I've never seen a report of a pool owner who used such a product and was happy with the result.

By any chance, were you using Trichlor pucks/tablets as your primary source of chlorine? Also, what, if anything, were you using for regular shocking?

If you want some more education on how to maintain your pool and what the various terms mean, etc., take a look at the Pool School.


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