Recommended Free Chlorine Level - Old vs. New School?


May 22, 2020
Dallas, Texas
I noticed that most strips and lower-priced test kits show 1-3ppm of Free Chlorine as the ideal level.
But according to this forum this is not accurate (FC as a factor of CYA, among other things) .
So where can I read about the study/evidence that supports this?
And how new is this "second school of thought"?
I'm really puzzled that the FDA (I think) has a recommendation that is outdated, as well as the test kits.
Thanks in advance!


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV

There are no federal regulations pertaining to residential pools. The EPA only states there are three approved sanitizers for pools, chlorine, bromine, and baquacil.
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Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
Franklin, NC
Actually, the EPA regulates pool sanitizers, not the FDA.

You know, it's actually a long story and the scientific documents that support this system go back to the 1960's. Basically, a pool technician back in the 90's started noticing differences in how pools reacted to differing amounts of chemicals, specifically chlorine and CYA. As many do he stared an internet forum that attracted a lot of attention form pool geeks. Well, one of those geeks, known as Chem Geek has a scientific type of mind and began digging around to document why this was happening. Guess what, he found peer reviewed published documents that identified exactly what was going on.

Chem Geek has posted a lot of the information he discovered and I see there are already links to his longest document that talks about almost everything. As to why the industry hasn't moved, who knows?? I generally say follow the dollars.

But, if you really need some bedtime reading, here are just a sample of the papers the system s based on-