Combined, Total & Free Chlorine: Top Guide on Its Differences and Similarities

In order to get the most out of your chlorine, you need to know what the difference is between the different types of chlorine. Here’s a description of the three types of chlorine available in swimming pools.

One of the essential parts of maintaining a swimming pool is keeping chlorine levels in proper levels for clean and sanitized water, but did you know that there are three types of it?

Chlorine is an element that can be used for swimming pools, spas, and hot tubs. It is a potent oxidizing agent that helps kill bacteria and other pathogens.

With this product, you get a lot of benefits that will help your pool stay clean and healthy. It provides consistent pH levels and serves as a protection against algae. But you might wonder, what’s the difference between these different types? 

chlorine tablets display

If you want to understand better about the three types of this compound or any other aspect, then read on! This article will help you know how you can keep a healthy swimming environment for everyone in the family.

What Is the Difference Between Combined, Total, and Free Chlorine?

chlorine and test strip beside pool

You may have come across words like free, mixed, or total chlorine. So let’s get this straight and figure out what they’re talking about.

What is Free Available Chlorine (FAC)?

This is the sort of compound that you should be looking for in your pool. Just like a speck of invisible magic dust floating around, the FAC is unused and accessible to clean your swimming pool water, and it is simply waiting to be used.

This specific sort of product is quite essential for pool sanitation. If there isn’t enough FAC in the water, you’ll not be able to get rid of the bacteria and other pollutants that have accumulated in your pool’s water. 

What is Combined Chlorine?

This is the one that has been used up and has already completed its disinfection task in your pool. It’s exhausted, overworked, and depleted — but it still has significance. It is still prowling around in your swimming pool. Waiting.

When the FAC is added to pool water, it oxidizes pollutants such as nitrogen and ammonia, which helps to disinfect the water. The available chlorine is then depleted, combining with the pollutants it is acting against, and becomes combined chlorine. This is also the process through which chloramines are formed.

For some instances, little amounts of combined chlorine remain in the water, but its sanitizing power is diminished compared to the FAC.

What is Total Chlorine?

This one is the sum of FAC and Combined Chlorine.

As opposed to FAC or combined chlorine, this one is easier to detect in water, which is why many of the cheap measurement tests will only measure this.

In clean water, the total chlorine level is used to determine the amount of FAC available in the water, so combined chlorine should be at zero. 

For some instances, however, if the cheap measurement test detects combined and FAC, total chlorine measurement is essentially useless.

So, yes, measuring total chlorine is usually inexpensive, but it is not nearly as effective; that’s why you should strongly consider purchasing sensors that detect both types of the compound. 

Insiders tip: By using a low-cost testing kit or test strips that detect total chlorine, you may save money on the cost of testing equipment.  Under typical circumstances, you may simply assume that total and free chlorine are the same things. 

Moreover, in the event that you discover any algae in your pool or notice a lingering chlorine odour, you should shock your pool. To know more about pool shock, check out this article. 

Testing Methods

Maintaining the levels of chlorine in your pool is vital to keep your pool pristine blue and healthy. While it’s suggested that you test your pool water at least once a day, you’d be okay if you test your water every other day.

The need to test your pool water is essential if your pool is kept uncovered, exposing it to the elements such as sunshine, rain, leaves, and wind.

There are three methods for testing free, combined, and total chlorine levels in your swimming pool water. These include test strips, test kits, and digital testers.

Test Strips

Test strips are usually a simple device you dip in your pool. These can be made of plastic, paper, or metal, and they’re small and easily portable. The strip will change colour as the chlorine level changes, showing if it is below or above tolerable limits.

chlorine tablet and test strip

Test Kits

Test kits can detect chlorine levels quickly with no large amounts of water. These can be used by simply dipping a sample into them using available testing tips provided with them. These test kits are a popular choice among pool owners.

chlorine test kit beside pool

Digital Test Strip

Digital test strips are growing in popularity, as this is the newest method for testing chlorine levels. Using a small probe-like device, it is possible to test free and total chlorine levels in your swimming pool water. These are used in conjunction with a digital tester.

Digital Chlorine Test Strip

Put Free, Combined, and Total Chlorine All Together

If FAC and total chlorine have the same levels, there’s no available combined chlorine in your pool’s water, which only means the compound has not been utilized up yet. 

If the total chlorine level is greater than the FAC, the difference between the two is usually the combined chlorine level. 

In other words, FAC levels must be greater than combined chlorine levels for your pool to maintain adequate sanitization. This is why you must test your pool water regularly. You can easily do this regularly with test strips or liquid test kits. 


As you gain more knowledge about pool care, you’ll come to understand the significance of chlorine (mainly free and combined) in maintaining safe and clean pool water.

Now that you’re familiar with some terminologies, you’ll be able to test your pool to ensure that it remains clean and sterilized throughout the whole year.

If you want to know more about keeping your pool clean, safe and healthy, here are some articles that may help you. Happy swimming!

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About the author

Brian Anderson

The rather dry pool world out there is in need of some passion to make it shine. With the help of my son Ruben and his wife Maria our mission is to help you create the favorite spot of your house - your pool.

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