As pool water pH rises, less of the chlorine is in the killing form and more of the chlorine is in the weaker form.

[willygee]

Quote from some of my older notes: As pool water pH rises, less of the chlorine is in the killing form and more of the chlorine is in the weaker form.
Wondering what PH values they are referring to.

 

[JoyfulNoise]

This is only really true when no CYA is present. When cyanuric acid is present in pool water, most of the chlorine is bound up as reserve chlorine and, if you follow the TFP FC/CYA recommended ratio of 7.5% for manually chlorinated pools, there will be ample amounts of "active" chlorine (the kind that kills) no matter what pH your pool water is if you stay within the recommended range of 7.2 to 7.8.

You can find all of the detailed chlorine chemistry in this thread - Pool Water Chemistry

 

[willygee]

Thank you Jnoise for the clarification...pun intended