Quote Originally Posted by PoolDoc View Post
+ Analytical observation: Beginning around 2005 (I'll let him comment on this) Chem_Geek took earlier laboratory research and distilled it into an analytical spread sheet that allows calculation of actual HOCl, and -OCl levels, given DPD chlorine levels, pH and CYA levels. Over the past 8 years, both here and at TroubleFreePools, an increasing body of empirical evidence has validated his analytical conclusion that the EFFECTS of chlorine in water are primarily a function of the HOCl and -OCl components. Stabilized chlorine compounds in the water constitute an effective and instantaneously available chlorine RESERVE, but are not themselves active, until the HOCL levels are reduced, allowing the stabilized chlorine compounds to release their 'reserve'.
I moved into a new house that we rebuilt and added a pool in 2003 and used Trichlor pucks in a floating feeder. After one and a half seasons, so halfway through 2004, I started to get an unexplained higher chlorine demand and had a hard time keeping up with the Trichlor pucks, even putting them into the skimmer to dissolve them more quickly (bad to do, but I didn't know that at the time). The water started to turn dull to cloudy. That's when I started looking around for answers and ran into The PoolForum and PoolSolutions where I read about shocking my pool with chlorinating liquid or bleach to kill the algae, getting a proper test kit, checking my CYA level, etc. After lurking for a while, I joined in November, 2004.

I also started to do research to see if I could figure out the chemistry behind the chlorine / CYA chart. I wrote a horribly complex spreadsheet, initially for the saturation index to match the Taylor watergram, but then added the chlorine/CYA equilibrium equations I eventually found that were definitively determined in 1974. I continued to find more and more evidence in scientific peer-reviewed papers in respected journals that this relationship held for pathogen kill times, oxidation rates, ORP levels, etc. The actual algae inhibition levels were determined by Ben through observation. My only contribution for my version of the chart was to "normalize" the values in the table to make them more consistent with the chemical theory.