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is residual chlorine same as free chlorine

by:BOQU     2023-04-25

Residual chlorine often gets confused with free chlorine, and people often use these terms interchangeably. However, there are some differences that are worth understanding. In this article, we will dive into the technical differences between residual and free chlorine, and how they affect your water quality.


What Is Chlorine?


Chlorine is a common disinfectant used in water treatment facilities to kill bacteria and viruses that can cause waterborne diseases. It’s also used to maintain the general cleanliness and hygiene of swimming pools, hot tubs, and spas. Chlorine comes in various forms, including sodium hypochlorite, calcium hypochlorite, and chlorine gas.


What Is Free Chlorine?


Free chlorine is the amount of chlorine left in the water that has not reacted with contaminants. In other words, it’s the part of chlorine that is still available to kill bacteria and viruses. Free chlorine is measured in parts per million (ppm) and should be maintained at a level of 1-3 ppm in swimming pools and hot tubs.


What Is Residual Chlorine?


Residual chlorine is the amount of chlorine left in the water after it has reacted with contaminants. In other words, it’s the chlorine that has done its job of killing bacteria and viruses but is still in the water. Residual chlorine is measured in parts per million (ppm) and should be maintained at a level of 0.5-1 ppm in swimming pools and hot tubs.


Residual Chlorine and Free Chlorine: What's the Difference?


The main difference between residual and free chlorine is that residual chlorine has already reacted to disinfect the water, while free chlorine is available to do so. Residual chlorine is measured after the chlorine has done its job and is no longer available to kill bacteria and viruses. Free chlorine is measured before the chlorine has reacted with contaminants and is still available to kill bacteria and viruses.


Why Is Maintaining Residual Chlorine Levels Important?


Maintaining residual chlorine levels is important because it ensures that there is enough chlorine left in the water to continue killing bacteria and viruses. If the residual chlorine level drops too low, it means that the chlorine has already reacted with contaminants and there is not enough chlorine left to kill remaining bacteria and viruses. This can create an environment for harmful bacteria and viruses to grow and thrive, increasing the risk of waterborne illnesses.


How to Test for Residual Chlorine?


To test for residual chlorine, you will need a test kit that measures chlorine levels. These test kits can be purchased from pool supply stores or online. Collect a water sample in a clean container, follow the instructions on the test kit, and record your results. If your residual chlorine levels are too low, add more chlorine to the water until the desired residual chlorine level is reached.


Conclusion


In conclusion, residual chlorine and free chlorine are not the same, but both are important to maintain water quality. Free chlorine is the amount of chlorine available to kill bacteria and viruses, while residual chlorine is the amount left in the water after it has done its job. Maintaining residual chlorine levels is important to ensure that there is enough chlorine left in the water to continue killing bacteria and viruses. Remember to test your water regularly for residual chlorine and adjust your chlorine levels accordingly, to ensure the safety and clarity of your water.


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