Chlorine vs Bromine: Which Is Best for Your Hot Tub?

Chlorine and bromine are the most popular choices when it comes to sanitizing hot tubs, but is one really better than the other? Which should you use and why?

Bromine is far more practical than chlorine as it has greater stability at higher temperatures, is better at killing bacteria, requires less maintenance, and is gentler on skin. Although chlorine is less expensive and faster acting, its lack of stability in warm water makes it more suited to pools.

As with most things in life, what’s good for one person is bad for another. This article is going to take a look at 10 different pros and cons so you can decide which is best for your circumstances.

Chlorine vs bromine: 10 pros and cons

1. How they work


When you add chlorine to your spa, it attacks and destroys contaminants from the inside out. It steals electrons from these contaminants and changes their molecular structure. This process is known as oxidation. 

During this process, chlorine dissipates and leaves behind a waste product known as chloramines. 

Chloramines are responsible for the stinging and drying smell that comes from your spa. They also reduce the effectiveness of sanitizers. Bathers can notice chloramines even at levels as low as 0.2 parts per million (ppm).


Bromine, on the other hand, works as an ionizer. It combines with bacteria and forces apart their chemical bonds. 

Like chlorine, bromine also produces a waste product known as bromamines. Bromamines are not as harmful and smelly as chloramines; however, they reduce the effectiveness of bromine in your hot tub. You can eliminate bromamines by shocking your spa.

2. Effectiveness


You can measure the effectiveness of a sanitizer by its reactivity rate. Reactivity rate refers to how quickly the sanitizer destroys contaminants. 

Chlorine is used to eliminate algae, bacteria, and other pollutants in your hot tub. It is more effective than bromine because it kills contaminants more quickly.

The chlorine in your spa is divided into two: free available chlorine (FAC) or combined chlorine (also called chloramines). Also, when you add chlorine to your spa water, it forms hypochlorous acid (HOCl). 

HOCl is a potent disinfectant that makes up the free chlorine in the water. Apart from HOCl, free chlorine also contains hypochlorite ions (OCl-). However, HOCl is much stronger than OCl-.

The effectiveness of the free chlorine depends on the pH of the hot tub water and the amount of HOCl that is available. 

At a pH level of 7.2, nearly 67% of free chlorine is in the form of HOCl. At a pH level of 7.5, nearly 50% of free chlorine is in the form of HOCl. And at a pH level of 7.8, it drops to almost 33%.


Bromine is a very reactive element, but it’s not as reactive as chlorine. It kills contaminants more slowly than chlorine. 

Additionally, bromine has a lower and more stable pH than chlorine. It keeps your overall water chemistry more balanced and reduces the need to adjust your water chemistry regularly. 

Bromine is more effective at killing bacteria and viruses, but chlorine has a higher killing power when it comes to algae.

3. Health and safety


Both chlorine and bromine are safe to use, provided you use them in proper amounts. However, using excess amounts can pose serious health issues. 

For instance, excess chlorine can cause sore throat, chest tightness, coughing, and wheezing. In addition, chlorine contains bleach which can cause skin and eye irritation. 

Chlorine also has a strong smell that can make it difficult for you to breathe and even trigger asthma attacks.


Bromine doesn’t contain bleach and is known to have an imperceptible odor. Additionally, there are fewer cases of bad eyes and skin reactions when people use bromine.

However, if bromine is not used safely, it can harm your health. For instance, breathing in bromine gas can give you watery eyes and a headache. The gas can also irritate mucous membranes. Additionally, bromine liquid or gas can cause burns and irritation on your skin.

Bromine is gentler on your skin than chlorine but it has a higher staying power that causes it to last longer on your skin.

Bromine is a better choice for people with sensitive skin or respiratory difficulties. But it is not suitable for people allergic to chlorine since bromine is also chlorine-based.

4. Cost


Chlorine is less expensive than bromine. For instance, Trichlor 1” chlorine tablets are about 20% cheaper than bromine tablets, while the 3” tablets are over 40% cheaper when you buy them in bulk. 

Chlorine granules are slightly more expensive than chlorine tablets; however, they’re still cheaper than bromine granules.

Although chlorine is cheaper than bromine, you may need to use it more often. The cost also depends on the size of your hot tub and how well you maintain clean and balanced spa water.


Bromine, on the other hand, is a much more expensive product. You can expect to pay almost double the price of chlorine for it. For instance, 50 pounds (23kg) of chlorine will usually cost about $150, while the same amount of bromine will cost about $300. 

Another thing to consider is the cost of equipment. For instance, if you use chlorine tablets, you may have to spend around $20 on a floating feeder for dispensing. In the case of bromine, installing a bromine feeder can cost you between $150 and $400. 

The upside to using bromine is that you don’t have to use it as often as chlorine. Because of this, it’s possible that the cost of using bromine and the cost of using chlorine may turn out to be the same.

5. Convenience


Chlorine is more convenient to use compared to bromine. Simply purchase a small quantity of 1 inch chlorine tablets (3 inch tablets dissolve very slowly) and put enough in a floating dispenser to obtain a good reading when you test the water.

If, for instance, you want to stop using chlorine in your hot tub and you want to change to bromine, you can easily switch. It’s a much easier process than switching from bromine to chlorine. All you have to do is stop using the chlorine tablets and start using bromine tablets instead. 

However, you must replace the chlorinator or tablet feeder before you switch to bromine. You need to do this because there would be chlorine residue left in the chlorinator and you don’t want it to come in contact with bromine, because this could be dangerous.


Switching from bromine to chlorine is quite tedious. Bromine contains bromide ions that can convert chlorine to bromine. So, if you add chlorine to your spa without removing these ions, they will change the added chlorine to bromine, making the whole attempt pointless.

To get rid of these ions, drain the hot tub completely, clean the surfaces thoroughly, rinse down the spa, and allow it to dry. After it dries, you can then refill it and proceed to add chlorine. 

In addition, if you use a brominator, ensure you replace it with a chlorinator or chlorine feeder to avoid any dangerous chemical reaction.

6. Dosage


The amount of sanitizer you add to your hot tub depends on how much water it holds or how big the tub is. However, the ideal level for chlorine in a hot tub is 1-3 ppm. Chemical formulations are different, and each hot tub has its own specifications. 

Therefore, ensure you follow the manufacturer’s instructions and test the water before adding chlorine or bromine. This will help you decide whether adding more disinfectant is necessary.


The ideal level for bromine in a hot tub is 3-5 ppm. You may need to use a larger dose of bromine than chlorine to obtain the same sanitizing results. 

7. Stability


Chlorine dissipates more quickly than bromine. Therefore it is less stable than bromine. This is because chlorine is more reactive and performs sanitizing activities much faster than bromine.

Additionally, chlorine loses its effectiveness when pH levels rise. For instance, at a high pH of 7.8, only about 25 percent of chlorine remains active.

Although chlorine and bromine break down easily when exposed to sunlight, chlorine has an advantage. It can be stabilized by cyanuric acid (CYA), which protects it from the sun’s ultraviolet (UV) light. This makes chlorine a more suitable sanitizer for outdoor spas. 


Bromine kills bacteria in your hot tub for a longer period than chlorine. It is much more stable than chlorine, especially in warm water or at high temperatures. 

Bromine remains stable above 75°F (24°C), whereas chlorine is more effective at lower temperatures such as 65°F (18°C). This is why most spa owners prefer bromine to chlorine. 

However, when bromine is exposed to the sun, it dissipates much faster than chlorine. This is because bromine doesn’t have CYA or anything to protect it from UV light. The only way to protect bromine from ultraviolet light is by keeping your spa covered. 

In addition, bromine is not affected by pH swings. It remains stable and effective even when the pH levels in a hot tub rise quickly.

8. Water transparency


Chlorine removes not only bacteria but also organic matter like sweat from the water. This helps to keep the water clear.


Bromine, on the other hand, has a lower pH, making it less efficient at removing organic debris. This leads to a cloudy appearance of your spa water. 

9. Shocking Procedure


Chlorine is both a sanitizer and an oxidizer. When you shock your hot tub water with chlorine, it combines with bacteria and destroys it. After which, the chlorine is burned up and eliminated by the filters.


Bromine, however, is only a sanitizer. When you add it to the spa water, it takes a while to activate, but it remains active even after killing the bacteria in the water.

10. Application


You can apply chlorine in three different ways: liquid, tablets, or granules. You can add the liquid and granules to the water without using any specialized equipment. The tablets, however, are placed in a floating dispenser to maintain adequate chlorine levels in the hot tub water.

When applying chlorine granules, follow these steps:

  • Determine the volume of your hot tub and how much water it holds.
  • Ensure the hot tub is running.
  • Read the instructions on the container carefully.
  • Measure the amount of sanitizer recommended by the manufacturer for your hot tub’s volume.
  • Pour the chlorine granules slowly and directly into your spa.
  • Allow the spa water to circulate for 20 minutes so the sanitizer can disperse.
  • Test your water to ensure proper sanitizer levels and make adjustments as necessary.

When applying chlorine tablets, follow these steps:

  • Read the instructions on the container carefully.
  • Place the recommended number of tablets into a feeder.
  • If the feeder is adjustable, adjust it according to the manufacturer’s instruction to control the release of sanitizer.
  • Hold the feeder under the water for a few seconds to push out the air and keep it more stable as it floats.
  • Test your water to ensure proper sanitizer levels and make adjustments as necessary.


Bromine also comes in granules and tablets. It is best dispensed through a cartridge dispenser or floating feeder. The above directions for chlorine granules and tablets also apply to bromine granules and tablets. 

Can I mix bromine and chlorine?

You shouldn’t mix bromine and chlorine together because this can cause a dangerous chemical reaction. Do not mix them together in the hot tub water, and do not mix them together in their dry state.

Additionally, do not store them together, even if they’re in separate containers. This is because the fumes they give off can combine and become combustible.

Joshua Milton

Joshua Milton is a seasoned hot tub enthusiast. With many years of experience in the industry, he offers valuable insights on hot tub maintenance, health benefits, and relaxation techniques.

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