Which chlorine to disinfect your water?


Our chemistry expert explains everything you need to know about treating your pool or spa water.



There are 3 different chlorines: active chlorine, free chlorine and total chlorine.

The water in your pool or spa contains several types of chlorine but beware! not all of them participate in the disinfection of the water. You should also know that not all clore measurement solutions on the market, such as strips, will measure the chlorine that is effective against the appearance of bacteria. It is therefore very important to understand what needs to be measured in order to know how to treat your water with what dosage.

  • Total Chlorine: this is the total chlorine in your pool and is composed of free chlorine and combined chlorine, also called chloramine.
  • Free chlorine: it is composed of active chlorine and potential chlorine. Measuring free chlorine can only give a partial view of the health of your water.
  • Active Chlorine: If you have to remember only one, it is this one! Active chlorine is the only chlorine that acts in water disinfection.
  • Potential chlorine: this chlorine is not yet transformed, it can become either active chlorine or neutral chlorine. In this state, potential chlorine does not disinfect.


Choose the right solution to measure active chlorine, responsible for water disinfection


To control the level of disinfectant present in the water, you need to measure the active chlorine.On the market, there are different solutions to measure chlorine such as strips or electronic testers. Most of them measure free chlorine or total chlorine (not responsible for water disinfection). The measurement of these solutions gives you a partial indication but not an accurate diagnosis to control the sanitation of your water.

  • By using strips, you do not measure active chlorine. However, it can give a trend of the quality of your water.
  • An ORP probe is the most reliable way to measure the disinfection level in your pool or spa.
    If you compare your ORP probe measurement and your strip, you now know that the chlorines being measured are probably not the same 🙂



You have a doubt about the sanity of your water?

Choose an ORP probe solution that measures active chlorine: this is the only chlorine that is responsible for water disinfection. You will be able to intervene more efficiently to keep your water healthy and clear in your pool or spa.

To manage your pool or spa, find all our videos on youtube Ondilo’s channel 

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