Question about the Chlorine/CYA ratio

[stev32k]

I don't understand the chemistry of the chlorine/CYA ratio, but wonder if there is any reason to maintain a higher or lower CYA concentration. Is there any advantage to maintaining say 40 ppm CYA over a 20 ppm concentration? The lower CYA number would require a lower chlorine number which would let my liquidator go longer between refilling and use less chlorine. I've been keeping the CYA at 40 ppm but not really sure if there is any good reason why it should be 40 instead of 20.

 

[JohnT]

You would probably use more chlorine at 20ppm. At 20ppm, you will probably struggle to keep your pool chlorinated in the middle of the day. The sun will destroy it faster than you add it, which can let your FC level get down to zero. Raising it to around 40ppm is a good compromise between protecting your chlorine while still allowing you to have a reasonable shock level if you need it.

 

[Isaac-1]

In other words a lot of it is about sun exposure, this means your optimal CYA level with a typical mid North America location with some shading will likely be around 40 ppm, with full sun you will likely want around 50 ppm, and prime sun belt location like south Florida may want even higher.