What is the difference between free and combined chlorine?

What is the difference between free and combined chlorine?

We start by designating the following three terms within the chlorine spectrum:

  • Total chlorine value

  • Active / Free chlorine value

  • Bound chlorine

The terms are explained below using examples:

The total chlorine value
This value indicates the total amount of chlorine in your water, but this does not say anything about the work of chlorine.

The total chlorine value consists of active / free chlorine and combined chlorine.

Active / Free chlorine value
This value indicates how much active chlorine your water contains. This level determines the disinfection and is between 0.5 and 2.5 ppm.

Bound chlorine
This is chlorine that is no longer active. It has done its disinfecting work and even counteracts the disinfection. It has a strong odor and can irritate eyes and mucous membranes.


It is therefore also that the lower the bound chlorine value, the better. In addition, the bound chlorine value must never be higher than the free chlorine value! Then the disinfection process will not work.

The following formulas can be used when calculating the chlorine values:

Free / Active chlorine + Combined chlorine = Total chlorine
Total Chlorine – Free / Active Chlorine = The Combined chlorine amount

We are happy to help you accurately and reliably measure and monitor the desired chlorine content with one of our measuring instruments. View our range of chlorine meters here.