What is Free Chlorine In a Hot Tub?

Chlorine is an essential chemical that cleans up the water of a hot tub and keeps it sanitized. As a responsible hot tub owner, you should keep track of the chlorine levels in your hot tub at all times. If the chlorine levels are high or low, you should bring them to an acceptable level so that the water of your hot tub is free from germs and bacteria.

Often, pool owners are confused about the different types of chlorine in their hot tubs. The difference between free chlorine and active chlorine is not apparent to them, and they often do not know how to test for a particular type of chlorine. Let’s first understand the different types of chlorine in a hot tub.

Free Chlorine – Most testing devices will test for free chlorine in a hot tub. This reading is the amount of chlorine present in the water of the hot tub that can sanitize the pool of all impurities and germs. In effect, this chlorine in the water is freely available in the water for all kinds of sanitization purposes. The recommended level of free chlorine in the water should be between 1-3 parts per million.

Combined Chlorine – Also known as Chloramines, this is the chlorine in the water that is actively fighting germs and bacteria in the water. You can think of it as chlorine that is in the process of cleaning your hot tub’s water. The chlorine molecules attach themselves to the impurities in the water and render the impurities inert. This type of chlorine in the water is less effective at cleaning the water as compared to free chlorine because it is in use. If there is a higher concentration of chloramines in the water, you will find a strong chemical smell near the hot tub.

Total Chlorine – This type of chlorine is simply the combination of free chlorine and combined chlorine.

How Does Free Chlorine work to Clean a Hot Tub’s Water?

Adding chlorine to the water in a hot tub creates hypochlorous acid and hypochlorite ion. The combination of these two compounds is known as chloramines. The presence of chloramines in the water means the water is in the process of getting clean.

But to ensure water keeps getting cleaned, the level of free chlorine in the water should be higher than combined chlorine. If the water test shows the combined chlorine levels going up, it’s time to add more chlorine to the water. Additional chlorine will balance the pool chemistry so that the chlorine keeps cleaning the water by destroying the bacteria.

Higher total chlorine levels mean it is not cleaning the water of the hot tub effectively. If you get such readings, you need to shock the water with an external agent like an oxidizer.

By shocking the water with another chemical, you will find that the levels of free chlorine have risen in the water. When you add an oxidizing agent, make sure you let the water run through the jets for twenty minutes before entering the hot tub.

The bottom line is that if you are looking for a properly sanitized hot tub, there should be more free chlorine in your hot tub than combined chlorine. Extra free chlorine will attack the bacteria and germs in the water and sanitize the water.


There is no doubt that the distinction between free chlorine, combined chlorine, and total chlorine can be severe at first. But with a little thought and understanding, you can keep the water in your hot tub clean and well sanitized. Make sure you take regular readings and adjust the levels of chlorine as needed. All it takes is a little foresight and understanding of the water chemistry to enjoy a healthy and refreshing time in the hot tub.

For any queries about free chlorine in your hot tub, feel free to leave a comment, and our team will answer your question at the earliest.


How to Raise Free Chlorine in Your Hot Tub


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Hi, I'm Richard the Chief Editor at HotTubDigest.com. I worked in the Hot tub maintenance field for a few years, and I thought to share my knowledge about Hot tub on our blog. My team and I share useful information related to Hot Tubs.

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