I have an excess of cyanuric acid in my pool even after half draining it three times. Help !

Paulina's Avatar (by Gravatar) by Paulina in  Yard » Pool 

The pool guys have been advising me to not use tablets anymore until I control the cyanuric acid level. Did that, but started seeing algae and still having high levels of cyanuric acid (150). Because of that the chlorine is not staying in the pool, so I need to schock 2 times/week with Calcium dichlor ; use algicide 2 times/week and brush the walls like crazy. I started using the tablets again to control the algae, half emptied the pool three times and the only thing I got was going from a level of 200 to 100 of cyanuric acid. Can a kit named "No drain acid wash" would help me get rid of this excess of cyanuric acid? Thank you so much for helping me with this. I'm tired of being a slave of my pool

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Answer by richardfalk

The following are chemical facts independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So by your using Trichlor tabs you are increasing your CYA level. If your chlorine usage were 2 ppm FC per day, then you'd increase CYA by 36 ppm per month. There is no such thing as "Calcium dichlor" for shock -- you are either using Dichlor or you are using Cal-Hypo.

I strongly suggest you look at the Pool School at Trouble Free Pool if you want to learn how to get out of this cycle by mostly using chlorinating liquid or bleach as your primary source of chlorine, after you do partial drain/refill to dilute your pool water to lower your CYA level.


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