The differences between free, total, and active chlorine.
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.
As you can see in the illustration below, chlorine, once in the pool water, is divided into different active or inactive 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.
Active chlorine is the active form, effective against bacteria, viruses, and algae.
Combined Chlorine = Chloramines are 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!
What about the ORP?
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.