pH balancing is commonly thought of as a way to minimize skin irritation and while that is one of the reasons you don’t want to swim in a misbalance body of water, it is not the real reason pool operators are concerned with pH. Chlorine activation levels are tied to the pH level of your water, and there is a sharp decline in the activation of chlorine as your water becomes more alkaline. If chlorine is not in an active state it cannot react with and neutralize organic materials and will not play its role in keeping your water sanitary. Chlorine likes to function in acidic condition and will have a 97% effectiveness at a pH of 6.0 however that would be far to harsh on our eyes and skin; on the other end is your pools pH is allowed to creep up to 8.0 the chlorine effectiveness will have dropped to 3%. While both of these pH levels are well outside of the pH range required for comfortable swimming it illustrated the point that pH is pivotal in the sanitation of your water. On the low end of acceptable (7.2 pH) your free chlorine will be 63% effective while on the high end (7.6) it will have dropped to only 39% effective. There is a very aggressive decline in free chlorine effectiveness in the mildly alkaline range, so it is important to keep a close eye on the pH level in your water. 7.4 is the widely accepted optimal pH level as it is the pH found in the mucus membranes of the human eye and will cause the least irritation for a swimmer, but it is important to remember that the sanitation ability of your chlorine is dependent on the pH not getting too far away from the acidic end of the spectrum.
By Will McMordie