What is the Difference Between Free Chlorine and Total Chlorine?

So we get the question "what is the difference between free chlorine and total chlorine" more than you would imagine. So we decided to write about it and clear up any confusion. 

One of the most frustrating aspects of maintenance for new pool owners is ensuring accurate proportions of chemicals.

How much chlorine is needed? Since when is there more than one type of chlorine? Our goal is to help ease the frustration when cleaning and maintaining your pool, so in this post, we’re going to cover the difference between free chlorine and total chlorine.

Free Chlorine

This is what comes to mind when we hear about chlorine. It is the type that you will initially pour into your pool for sanitation.

Its ideal level is usually based on parts per million, which basically means that you’ll need, for example, to have 1 - 3 milligrams of free chlorine per liter of water.

If that doesn’t help much, the owner’s manual for your pool should contain more detailed information for how much chlorine it needs (some pools are a little different).

On the scientific side, chlorine invokes a slight chemical reaction when added to pool water. The result is a combination of chlorinated compounds called hypochlorous acid and hypochlorite ion.

Ultimately, it is these chemicals that make up “free chlorine”. The goal of causing this chemical reaction is to kill harmful organic matter and destroy dirty compounds in your pool through a binding process. However, this process is what creates combined chlorine.

Combined Chlorine

Combined chlorine isn’t always harmful, it’s simply ineffective.

Once chlorine has become “combined” with other compounds (nitrogen and ammonia are among the most common, but there are many others), its job has been fulfilled.

As such, its effectiveness becomes significantly reduced; usually, in fact, 25 times less. So while the chlorine itself may not be harmful, the chances are high that the matter contained within your pool is.

Total Chlorine

Total chlorine refers to the total concentration of used (combined) chlorine and free (effective) chlorine. In other words, it is exactly what it sounds like; the total amount of chlorine in your pool.

Just remember, it is NOT the same thing as combined chlorine. Combined chlorine refers to chlorine that has actually bonded with other particles, not the overall amount.

This is where it can get a little tricky. Obviously, you want more free chlorine in your pool than combined. This is why we frequently shock our pools; it serves as an effective boost to free chlorine.

But, too much chlorine is unhealthy. It’s important to carefully review the directions included with your pool and your testing kit.

It’s also best to stay out of the pool after treating it for up to 24 hours!

You’ll need to use a testing kit to determine the proportions of each type of chlorine in your water. These are usually pretty cheap and easy to use.

However, the use for each one can vary slightly, so be sure to read the instructions. Test strips are the most common testing method and offer a simple visual clue of your pool’s chlorine content.

Check out this Video on the Difference Between Free and Total Chlorine 

Now that you know the difference between free chlorine and total chlorine, you can better test and sanitize the water in your pool! There’s really no need to be put off by hesitation.

Like everything else, it just takes a little time to become accustomed. And, as we’ve mentioned, your pool, chlorine treatments and testing supplies all include instructions for the proper testing of chlorine.

We hope this article on the difference between free chlorine and total chlorine has been informative and we thank you for visiting. 

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