Difference Between Free Chlorine and Total Chlorine (With Table)

Understanding the distinction between free chlorine and total chlorine might be difficult. You may easily be confused between these two chlorines without understanding the concept between them. Generally, we may know that they are used to sanitize the water from all contaminants, especially in the pool. The article will discuss the difference between free chlorine and total chlorine.

Free Chlorine vs Total Chlorine

The difference between free chlorine and total chlorine is the presence of chlorine in the water. Free chlorine is the amount of chlorine that remains from the actual chlorine and is available to sanitize the contaminants present in the swimming pool to get rid of harmful microorganisms and bacteria. Total chlorine is free chlorine plus combined chlorine. 

Free chlorine is referred to as the amount of chlorine that is used to kill harmful microbes and other germs. It is also used to neutralize the contaminants. It is free chlorine that is used to kill harmful microorganisms present in the swimming pool. It is the most effective type of chlorine that is actively responsible for sanitizing the pool.

Total chlorine is the grand sum of free and combined chlorine. Total chlorine can be calculated as 

      Total Chlorine (T) = F+C (free chlorine + combined chlorine)

The amount of total chlorine will always be equal to or above free chlorine amounts.

Comparison Table Between Free Chlorine and Total Chlorine

Parameters of ComparisonFree ChlorineTotal Chlorine
DefinitionFree chlorine is the quantity of chlorine needed to kill microorganisms that are present in the water.Total chlorine is the combination of free and combined chlorine
FormulaNo specific formulaT= F+C
ComponentsIt includes the chlorine available for the sanitization of water in a poolIt is the chlorine that may be available or not for the sanitization of water in a pool
ValueFree chlorine has a lesser value than total chlorineTotal Chlorine is superior in value as compared to free chlorine
UsageUse to kill germs and microorganismsUse to kill germs and microorganisms

What is Free Chlorine?

Free chlorine is referred to as the chlorine that is present in the water to kill some microorganisms in the pool. The interesting fact is the reduced presence of free chlorine than that of total chlorine. Free chlorine is in the form of hypochlorite ions, dissolved chlorine gas, and hypochlorous acid.

Hypochlorous acid is usually used for the measurement process because it has a strong oxidizing effect and is considered to be stronger than the hypochlorite ions. Concentration in the water of a swimming pool can be measured by the presence of chlorine which is available for the purpose of sanitization of contaminants. It is viable to measure the chlorine content present in the water. In the process of sanitization, the amount of chlorine is consumed by water in the pool. The best and the easiest way to check chlorine levels in the pool are with the help of test strips. 

Another two ways of measuring free chlorine are as follows

Colorimetric Test: It is the method in which some specific reagents and samples are required that can cause a colored integration in the water sample.

Amperometric Test: Amperometric is that system in which a rugged chlorine sensor compensates for ph level.

What is Total Chlorine?

Total chlorine is the economically viable test used to test the presence of both free chlorine and combined chlorine in the water. Combined chlorine is regarded as the amount of chlorine that reacts with nitrogenous compounds in the water of a pool. This chlorine does not affect the sanitization of water. Total chlorine allows the chlorine that may or may not be available for the killing of contaminants in water.

In simpler words, combined chlorine is referred to as the chlorine amount that is not present for the cleaning and sanitization of water. We can say that the amount of chlorine, when combined with nitrogenous compounds, makes water inaccessible for the sanitization process.

Organic amines and ammonia are the nitrogenous compounds that are present in water. These nitrogenous compounds may be found in polluted waters. Moreover, ammonia is added into the water for the process of chlorination which works as a sanitizer. Total chlorine is usually measured in the wastewater.

Main Differences Between Free Chlorine and Total Chlorine

  1. Free chlorine is the chlorine that is present to kill microorganisms, while total chlorine is free chlorine plus the combined chlorine.
  2. Free chlorine is used for the sanitization of water, whereas total chlorine refers to the quantity of chlorine that may or may not be available for sanitization purposes.
  3. Free chlorine always has a lower value, while total chlorine has a higher value.
  4. Free chlorine is usually checked by test strips, whereas there is a specified formula to measure total chlorine, which is total chlorine= free chlorine + combined chlorine.
  5. Free chlorine is used to sanitize the water. On the other hand, total chlorine is not used for the purpose of sanitization of the water.


Free chlorine and total chlorine are used to detect the quality of water and improve it. Free chlorine kills all the germs and contaminants in the water that can cause a variety of diseases. The difference lies in the quantity of chlorine that works against microorganisms.

Testing the chlorine quantity in the pool is important to ensure clean and clear water. Chlorine test can be done using chlorine test strips or a digital chlorine tester. Microorganisms may grow in the pool if your pool is uncovered, hence exposing it to sunlight, wind, and rain. Keeping the right amount of chlorine content is essential in maintaining pool hygiene. So, chlorine is an important additive to be used to kill pathogens and maintain pool hygiene.


  1. https://awwa.onlinelibrary.wiley.com/doi/abs/10.1002/j.1551-8833.1967.tb03388.x
  2. https://pubs.rsc.org/en/content/articlehtml/2001/gc/b104429j
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