Understanding the relationship between pH and Chlorine effectiveness

The disinfectant power of Free Chlorine is relative to the pH of the water.
As pH increases, the chlorine becomes less effective.  As pH decreases, the chlorine becomes more effective

pH Effectiveness of Free Chlorine
6.0  97%
7.0 75%
7.2 63%
7.5 49%
7.6 39%
7.8 28%
8.0 3%

Source: NSW Health Advisory Dec 2012

BUT if the pH is too low (acidic), the water will be corrosive to the pool surface and it will sting the eyes and irritate the skin. 

The desired pH range for a swimming pool is 7.2 - 7.6

To reduce pH, add acid
To increase pH, add Buffer


Did you know?   The pH of the human tear drop is 7.4.  Keeping your pool at the same level causes far less irritation to your eyes when swimming

If this seems too complicated, speak to us about salt chlorinators that can automatically sense and adjust the chlorine and pH levels in your pool.

Professional pool advice since 1981

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