What is the Difference Between Free Chlorine and Total Chlorine?

Difference Between Free Chlorine and Total Chlorine?As a pool owner you may know about the chlorine stuff. It’s a real confusion when you listen to terms like free chlorine, total chlorine or combined chlorine.

But, chill! We are here to answer you what is the difference between free chlorine and total chlorine. Just stick to the article till the last.

Let’s get into the main point!

What is the chlorine stuff and why should you care?

Chlorine is dedicated to killing bacteria through a simple chemical reaction.

When you are going to add chlorine solution into your pool, it will break down into many different chemicals, hypochlorous acid (HOCl) and hypochlorite ion (OCl-) are included.

Main job of both of these chemicals is killing microorganisms and bacteria and combining them with other chemicals (such as ammonia).

Unfortunately, chlorine can have many unpleasant side effects. It’s a strong chemical which contains a very strong odor.

What can be the result? It actually can cause swimmers to have itchy skin after a dip. At a worse case, the swimmers notice some color fading on their brand-new bikini. Bad enough!

What are the types of chlorine?

Now, let’s clear the confusion about free or combined chlorine. You will actually know what they mean.

1. Free available chlorine (FAC): This type is just unused and available and the type of chlorine what you test for in your pool. FAC just waits to sanitize your swimming pool water.

2. Combined available chlorine (CAC): This one is used-up chlorine that has already done its job. This means, it’s done with disinfecting your pool.

Though it’s overworked, tired and spent, still it does matter and still is lurking in your pool.

3. Total chlorine (TC): Simply, TC= FAC+CAC

Isn’t it easy? Now, we know the definitions, let’s know why these terms matter and how to test for them.

How to test for the three kinds of chlorine in your pool?

It’s important to test pool chlorine for keeping your pool water sanitized and clean. But, if you properly maintain chlorine levels in your pool, you’ll have clear, sparkling pool water as a gift.

You never want to step into a murky, cloudy pool, right? You can clear cloudy pool water later but you should test for water every day.

If not possible, at least get away with the testing stuff every other day. Moreover, frequent testing is a must for an uncovered pool that is exposed to rain, wind, leaves and sunlight.

Now, see the testing methods of chlorine level in your pool:

1. Chlorine test kits: Though chlorine test kits come in various shapes and sizes, all of them rely on the same process of titration. What you all need to do is to drop off a reagent.

It’s because you need to measure the amount of chlorine in the sample. The last thing you will do is to compare the color to the instruction sheet.

2. Chlorine test strips: These are made of plastic with chemical pads that are adhered to the sticks.

The chemical pads are already designed to react with water and change color to give a good estimate of free, total and combined chlorine levels in your pool.

3. Electronic chlorine tester: These are also known as digital chlorine testers. These devices will measure the chlorine levels in your pool without you having to compare colors manually.

What are the calculations you need to do?

Any form of chlorine added to water forms hypochlorous acid (HOCl) and hypochlorite ion (OCl-), so it has the same chemical reaction.

Free chlorine is the togetherness of HOCl and OCl- and this free chlorine is the active sanitizer and oxidizer that kills bacteria or germs from your pool.

Now, when the free chlorine is done its job and is depleted, the rest is there for you as combined chlorine. Combined chlorine is also known as chloramines and these are smelly and irritating.

Compared to free chlorine, combined chlorine is pretty ineffective and if it is at a high level in your poo, it’s bad news.

The simple equation about free, combined and total chlorine is:


From the equation, if your FAC and TC are the same, there’s no CAC in your water. It means, you don’t need to add any chemicals today!

Safe level of FAC

The recommended level of free chlorine is between 2-4 ppm (parts per million). Remember, never let it fall below 1 ppm. To be on the safest side, aim for 3-4 ppm.

Safe level of CAC

It would be best if you can keep the combined available chlorine (CAC) in your pool less than 0.2 ppm. But the maximum level is 0.4 ppm.

In case your pool exceeds that, you should take steps. You may even notice the POOL SMELL of chloramines at any level above 0.2 ppm of combined chlorine.

 An additional tip  for you is, if your free chlorine is higher than the combined chlorine, your pool is in good shape.

Continue frequent testing and monitoring, it will keep it that way. Using a liquid test kit or test strips will help to ease it.

Whenever you notice that the combined levels are going up, the time has come to rebalance the sanitizer in the water. Just add extra chlorine to your pool. What if the levels are low?

Nothing, you need to do nothing for this at all that day.


Still ‘what is the difference between free chlorine and total chlorine’ is a big question for you?

We hope your answer is NO! We tried to break down all the points as if you can take them easily.

Chemical balance is very important for your pool water. You need to check and keep it balanced regularly. It will help you to get a sparkling, blue swimming pool.

Keep your pool clean and be careful when you are working with the chemicals, because of the ‘safety first’ stuff!

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