Quick Definition:

Total chlorine is the sum of free chlorine plus combined chlorine in swimming pool water.

What is Total Chlorine in swimming pools?

In chlorinated swimming pools, total chlorine is the value of free chlorine added to combined chlorine, and is a simple math equation:

Total Chlorine  =  Free Chlorine  +  Combined Chlorine

Total chlorine is used as an indicator when checking pool chlorine levels.  Although this value should be tracked, the individual free chlorine and combined chlorine levels are more important to watch.

Test kits and some test strips can measure the total and free chlorine levels, which the pool tester can then subtract the free chlorine estimate from the total chlorine value.  If the value is above zero, then there is combined chlorine in the pool water, which the swimming likely needs to be shocked.  If the value is zero, then there is no combined chlorine in the pool, which is ideal.


  • “Pool & Spa Water Chemistry, A Testing and Treatment Guide, Waterproof Edition, 2005. Taylor”

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