Sharing article on relationship between chlorine and cya


Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
Franklin, NC
I find this part teh most interesting:

Lowry's re-examination of the CYA/chlorine relationship began as a result of his authorship of the Independent Pool and Spa Service Association's two chemical training manuals, which he wrote in 2006 and 2009 respectively.

"I received a correspondence from theoretical chemist Richard Falk," he recalls. "He told me that some of the information in the manual was incorrect, especially where CYA and chlorine are concerned."
Richard Falk is Chem Geek (here and other forums) who refined and expanded on the original Chlorine/CYA "Best Guess" chart to produce the Chlorine/CYA Chart by Chem Geek based on experiences with members on this forum and the old Pool Forum and conformation to chemical theory. Chem Geek is currently a member of teh Ad Hoc Comittee on Chlorine Stabilizers of the The Council for the Model Aquatic Health Code. With a little luck they will be able to add the chlorine/CYA relationship to the Centers for Disease Control and Prevention’s (CDC) Model Aquatic Health Code (MAHC).
I’m still pretty new to pools (just bought a house with one last fall), but I had my first experience today of a person who was really concerned about my (high) chlorine level. I run a SWCG with a CYA of 60 or 70, and this kind gentleman was quite worried about my FC of 6.5. He’s a retired pool worker and master plumber and was at my house because of a plumbing issue. He asked about the pool and my chlorine (I had been testing when he arrived), and he was genuinely worried about my number. He didn’t want to see it over 4.

I asked about the Chlorine/CYA relationship, and he talked about CYA but didn’t seem to think the CYA level mattered to the chlorine level. It was distressing to me because I know he’s really only concerned about my family’s safety, and he truly believes the FC is too high. I trust the TFPC science, so my distress was over the fact that this man is now worrying unnecessarily about my pool. I’ll be seeing him soon and plan to give him a copy of this article to let him see where I’m coming from.

All that to say, this is a great article to share for those familiar with the pool industry and concerned about chlorine levels from TFPC. Thanks for the link.


LifeTime Supporter
TFP Guide
May 14, 2015
Cartersville Ga
I don't think it can be done. From what was explained to me, the reagent that you use to measure the FC, unbinds the CYA and causes almost all the FC to be available to the test.