What is the purpose of CYA?

[chimerahitman]

Hello TFP,

When I look at CYA and its intended purpose I feel a bit hazy at the head. I understand that CYA will prevent wasteful use of bleach, but how does one determine the correct level?

If I have to much CYA, it is expensive to keep the correct levels of bleach since I would need more, especially at SLAM. Same with none, I would always be babying the pool to keep the levels of bleach high enough.

I live in a hot, 30-35 degrees Celsius sunny all day climate. Can anyone try to explain why some go for 30, others 40 or maybe even 50 ppm of CYA?

I once saw a line graph of cya vs chlorine vs XXX but I can't seem to find it.

Please orient my lost ways,
Thank you

 

[jblizzle]

The higher the CYA, the more protection of the FC from the sun. While the absolute level of the FC that is required for a higher CYA is also higher, the daily losses are similar or less. So the higher CYA results in LESS chlorine usage for maintenance. The problem with higher CYA is that the SLAM level is a lot higher if you run into a problem.

Given your climate, I would suggest a CYA of 50ppm as a good compromise.

 

[chimerahitman]

Thank you.

I will try it out.