Good article on CYA management from a pool industry source

[JohnT]

http://www.poolspanews.com/2008/052/052acid.html

A few quotes:
"Cyanuric acid, or CYA, is great at protecting chlorine from the sun’s UV rays. But if it isn’t regularly diluted with fresh water, the chemical, a byproduct of trichlor and dichlor tablets, can quickly escalate to unwanted levels, well beyond the 30- to 50 ppm industry standard."

"In fact, pools using stabilized chlorine may easily exceed CYA levels of 300- to 400 ppm.
That’s where the real trouble starts."

The article is written from the perspective of pool service folks, so they aren't too hot on using liquid chlorine since it doesn't really work for once a week maintenance, but it's nice to see mainstream industry folks with basically the same opinion about CYA as we have.

 

[chem geek]

I found where I have seen this discussed before -- it's in this thread in The Deep End (though Jason has a good response to this article -- it's in The Deep End due to further more technical discussions).

As we know, pools can have trouble long before the CYA level hits 300-400 ppm. We've seen even SWG pools with 80 ppm CYA get green algae at 2 ppm FC (sometimes 3 ppm FC). We've seen many manually dosed pools with 100 ppm and 3-4 ppm FC minimum (sometimes 5 ppm FC) get algae.

As Jason wrote, the article says nothing about the FC/CYA ratio or the FC and CYA relationship. The article has the Kent Williams PPOA chart for chlorine protection from CYA which we know is not correct based on Mark's experiments and others experiences that show that higher CYA levels even with proportionately higher FC levels can usually lead to lower absolute chlorine losses.

What is most interesting is that basic chemical rules of thumb are not in the article such as the following:

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 7 ppm.

In August, I sent an E-mail to the link given in that article for feedback where I wrote corrections to the article and linked to several of the detailed posts on this forum, but I never received a response.

Richard