Originally Posted by JasonLion
ORP readings don't take into account the pH.
Naturally the lower pH the higher your ORP will be, but the measurement of the ORP is just that. . a measurement in mV
regardless how low/high your pH is and regardless how low/high your FC is.
To put it simple ( without using chemical formulas and so on ) :
The higher the ORP the faster your "germ killing time" and the more effective your sanitizer will be working.
Example : pH = 7.2 FC = 0.80 ppm ORP = 780 mV
pH = 7.6 FC = 1.50 ppm ORP = 780 mV
Both examples give you the same "germ/bacteria" killing capacity of 780 mV.
Personally I run rather at the 7.2 pH and low FC than the other way around.
You also may want to read this whole article as well as the references at the very end.