We often talk about the level of chlorine in the water or the measurement of free chlorine. Be careful not to confuse free chlorine, total chlorine, active chlorine, or ORP of the water.

You may have noticed a difference between your chlorine level (expressed in ppm), and the disinfection potential analyzed by your EcO probe. This difference can be explained by the difference in the measurement of these different parameters.

As you can see in the illustration below, the chlorine, once in the pool water, is divided into more or less different active components.

  • Free Chlorine is the portion of disinfecting chlorine present in the water. It is divided into two parts, determined by the pH of your water. The higher the pH of the pool, the more active free chlorine will be reduced. Therefore, it is important to keep the pH between 7.2 and 7.4 to ensure optimum chlorine efficiency.

  • Combined Chlorine = Chloramines is the chlorine consumed by disinfection. After removing impurities from your water, the free chlorine is transformed into combined chlorine which is evaporated and creates that characteristic chlorine smell.

💡 There is no direct link between a strong chlorine smell and a high disinfection potential!

The ORP or oxidation-reduction potential is based on the proportion of active free chlorine in your water and its disinfectant power. It depends on the quantity of chlorine, but also on the pH of the water, (the higher it is, the lower the proportion of active chlorine), and the stabilizer rate.

This is why you may notice a difference between a raw chlorine measurement in the water and the ORP disinfection potential measured by the EcO water analyzer.

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