Will stabilized chlorine CYA reuse

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Will stabilized chlorine CYA reuse

Postby Lucian » Fri 04 Sep, 2009 13:29

I have a small Endless Pools outdoor pool, about 3000 gallons. It is covered tightly all the time except for 30 minutes a day when its used for exercise. I have been using stabilized chlorine and watching the CYA levels increasing gradually. Each year, CYA gets to about 120 or so, and I drain half the pool. Couldn't I let the CYA get to 50 or so and then switch to non-stabilized chlorine and let the CYA already in the water stabilize it? Or is that CYA not able to stabilize chlorine?


chem geek
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Will stabilized chlorine CYA reuse

Postby chem geek » Fri 04 Sep, 2009 13:49

You absolutely can switch to using unstabilized chlorine when the CYA level is even at 30 ppm since you probably don't need it any higher than that since the pool is covered -- I presume with a cover that is opaque to UV which is what breaks down chlorine. Use chlorinating liquid or 6% unscented bleach. As with any chemical added to the pool, add it slowly over a return flow with the pump running to ensure thorough mixing.

When ANY chlorine products are added to the water they all form exactly the same compounds. When there is CYA in the water, most of the chlorine is bound to CYA, but this is an equilibrium so regardless of the chlorine products you use this relationship occurs. If you add unstabilized chlorine, then most of it gets bound to the CYA. If you add stabilized chlorine (which is chlorine already bound to CYA), then some gets released as chlorine and some stays bound but the net result in both cases is the same and dependent only on the FC/CYA ratio.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm. So even with a low 1 ppm FC per day chlorine usage, the CYA will increase by over 100 ppm in 6 months when using Trichlor if there is no water dilution.

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