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Free Chlorine vs. Total Chlorine Explained

What Are Free Chlorine And Total Chlorine?

Not all chlorine is exactly alike. The subject of free chlorine vs. total chlorine is important to understand for anyone who is planning to buy a swimming pool.

When we think about chlorine and our swimming pools, we generally don’t think about the matter very deeply. We assume there is one type of chlorine. We assume it works to keep our water clean, and that’s the end of it. While it is certainly true that chlorine is a crucial part of our swimming pool, it is also true that there isn’t just one universal type of chlorine. With a little research, you will discover that there are in fact different types of chlorine out there. If you are serious about taking the best possible care of your swimming pool, then you will want to understand the differences between free chlorine and total chlorine.

free chrlorine vs total chlorine

There are technically three types of chlorine. We have total chlorine, free chlorine, and then what is known as combined chlorine. Really, in a lot of ways, combined chlorine is essentially the same as total chlorine, but there are a handful of small differences.

Mainly, we’re going to focus on the differences between total chlorine and free chlorine. It is important to understand the differences between these two entities. In order to properly care for your pool, it is going to be necessary to know how much of each of these types are in your water at any given time.  If you don’t know, there is a good chance that your water isn’t going to be as clean as you need it to be.

As chlorine is added to a swimming pool, it will dissolve into something known as hypochlorous acid. As time goes on, the chlorine will dissolve even further, creating something we call hypochlorite. This occurs as the weakened chlorine combines with oxygen. What we now have is an oxidizing ion that you can also find in bleach as its active ingredient. All of this taken together creates what we know to be free chlorine. It is essentially the chlorine that remains for the purpose of sanitizing your swimming pool.

Adding chlorine to your swimming pool will increase how much free chlorine is in the water. Most pool owners try to aim somewhere between one and three parts per million (also known as ppm). 3ppm is considered to be the optimal level.

In order to know the total chlorine (TC) levels for your swimming pool, we need to add your free chlorine (FC) together with the combined chlorine (CC). This is why it is important to keep in mind that free chlorine and combined chlorine are not exactly the same. By adding those two figures together, you will be able to get your TC in no uncertain terms.  At that point, you can easily discern whether or not your swimming pool is safe to use.

Combined chlorine specifically refers to when free chlorine has oxidized with such contaminants as ammonia and nitrogen. When this occurs, we have combined chlorine. This would also be how chloramines are created. Some chlorine does indeed stay in the water, but its sanitization potential has been dramatically reduced, compared to that of free chlorine.

Now, at this point, you are ready to understand how total chlorine exists. All you have to do to get your TC, as we mentioned before, is combine your free chlorine levels with your combined chlorine levels.

How Does Free Chlorine And Total Chlorine Work?

Are your levels exactly the same for both total chlorine and free chlorine? If so, you do not have any combined chlorine in your swimming pool. This means none of the chlorine has been utilized. However, if the total chlorine levels are in fact higher than your free chlorine levels, then you do have combined chlorine in the water. The difference between the two will be your exact amount on that front.

Where does proper swimming pool sanitization come into all of this? In order for your swimming pool to be in ideal condition for swimming and exercise, you will need to have your free chlorine levels at a higher level than your combined chlorine levels. A testing kit, which is available in a variety of different forms, and from a variety of different manufacturers, will tell you if your levels are out of whack.

You don’t have to be an expert on chemistry or math to understand optimal levels. By simply keeping in mind everything we have covered so far, you shouldn’t have any trouble in maintaining the proper levels. It all just comes down to making sure you have the right amount of chlorine in your swimming pool at any given time. If the levels aren’t right, the water can cause skin irritation and other issues.

Let’s take a closer look at the best ways to test the chlorine levels in your swimming pool:

  • Testing strips: A strip of plastic with a chemical pad, which then reacts to the water when submerged. The strip will then change color, which should tell you the total, combined, and free chlorine levels in your pool.
  • Testing kits: These are a little more involved than strips. You will also find that testing kits are offered in a seemingly endless array of sizes and shapes. Don’t let this aspect intimidate you. All of them are using the exact same titration process. All you will need to do, regardless of the specific kit you purchase, is add some reagent drops. This will measure the amount of chlorine in your sample. Compare the color you have been given to what you have in the instructions with the kit. This will tell you if your swimming pool levels are ideal.
  • Electronic testers: Also known as digital testers, these are designed to take all the guesswork out of measuring your colors by yourself.

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These are the testing options that can give you a clear idea of what you will need to do. Balancing the levels is easy enough if the test reveals the need for this. You may need to add more water, more chlorine, or both. Some prefer to call in the experts, but getting the levels right should be easy enough on your own. There are a number of different products available to you on the market.

Remember: Your ideal FAC levels are going to be in the neighborhood of 1-3ppm. Some say 4ppm is best, but you will ultimately have to make that decision for yourself. Your CAC levels will need to be around 0.2 to 0.4ppm. If your FAC or CAC levels drop below that point, then you definitely have a problem with the cleanliness and your pool.

Pros And Cons

The pros of keeping your levels optimal should be pretty clear at this point. Maintaining your swimming pool is one of the most significant aspects of ensuring its overall health. This part is easy to understand. What can prove to surprise new swimming pool owners is just how much work is seemingly being demanded of you. Ongoing pool care is definitely something you are going to want to understand in full detail before you decide to purchase a pool.

Maintaining your ideal levels for chlorine and everything else associated with the pool ensures something that everyone will be able to enjoy. Learning how to read these levels, and then knowing what to do about it, can be a little difficult initially. However, with time, you will find that these numbers, as well as the basic math involved, are simple enough to put into action.

Certainly, if you don’t want to find yourself spending money on professional work, you are going to want to learn how to handle all of this on your own. The pool you inevitably purchase will almost definitely include instructions for testing out your levels. Even if you don’t have any experience with testing and maintaining ideal chlorine levels, you will probably do just fine!

The downside of not taking care of these things is obviously a swimming pool no one will enjoy. Worse yet, pools that are not running at an optimal level can cause skin and eye irritations, as we mentioned before. Your swimming pool will go a long way towards keeping these contaminants out on its own. However, it will still need some help from you.


Chlorine is unquestionably the best friend your swimming pool is going to have. There are a number of different chemicals you may need to keep in mind when it comes to taking care of your swimming pool. However, chlorine is arguably the most crucial component for guaranteeing your swimming pool is something that everyone will be able to enjoy. Keeping in mind everything we have covered in the paragraphs above, you shouldn’t have anything to worry about. You will be able to maintain these levels with ease. Every pool owner can. It really just comes down to being consistent. Make it a point to check the levels of your swimming pool frequently. This can keep minor problems from turning into more expensive ones.

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