Bromine vs. Chlorine – The Best Sanitizer for Hot Tubs


You likely already know that bromine and chlorine are the most effective sanitizers for hot tubs and swimming pools.

But which one is better than the other?

You’ll soon find that out.

Let’s get started!

What are they?


Bromine is a chemical element with an atomic number of 35. It is a reddish-brown liquid at room temperature that easily evaporates. This chemical element is frequently used in insecticides, pharmaceuticals, dyes, and many more.

It’s also a known sanitizer for pools and hot tubs, although it’s more often used to sanitize for hot tubs because it works better in a hot temperature.


Chlorine is a chemical element with an atomic number of 17, and turns into a yellow-greenish gas at room temperature. It is mainly used as a sanitizer and a disinfectant for drinking and pool water.

How do they work?


Bromine-based products produce hypobromous acid and hypobromite ions to sanitize your hot tub. Hypobromous acid is mainly responsible for sanitizing your pool.

When bromine combines with ammonia, they form bromamines. But unlike chloramines, bromamines somewhat keep their ability to sanitize the water effectively.


When chlorine dissolves in your hot tub, it forms hypochlorous acid. This acid will bind with hypochlorite ion to form free chlorine, which actively fights against bacteria. Free chlorine has a high oxidation potential. In other words, it readily reacts with bacteria to destroy them.

When chlorine disinfectants react with organic contaminants (ammonia) in your pool, they form chloramines, a form of combined chlorine. Not only are these ineffective sanitizers, but they also lower the effectiveness of free chlorine. Furthermore, they cause irritations to your eyes and respiratory system.

So, you want to continually replenish your chlorine if you use it as the primary sanitizer to reduce the buildup of chloramines and keep the free chlorine level up.

How effective are these chemicals?


Bromine is fast-reacting and kills bacteria and viruses readily. Bromine is more effective at temperatures above 75 degrees F due to its stability. This makes bromine a better alternative to chlorine for hot tubs.

Due to its low pH compared to chlorine, bromine is not very effective at removing debris in the water. So you’ll often want to use bromine along with chlorine and shock to keep your water sparkling clean.

Although bromine doesn’t react as fast as chlorine, it remains active in the water even after it reacts with bacteria, which means you don’t have to add bromine as frequently as chlorine.

In fact, it suffices to add bromine about once a week in most cases.


Chlorine reacts even faster than bromine, so it’s capable of killing contaminants faster than bromine. It also tends to be more effective at temperatures below 65 degrees F, making chlorine better for swimming pools.

Not only is chlorine a sanitizer, but it is also an oxidizer. It burns off and becomes inactive when it reacts with bacteria and viruses, which is why chlorine needs to be refilled frequently. You’ll want to replenish chlorine at least once every few days.

Which one is more stable?

As previously discussed, bromine is more stable than chlorine, so it lasts longer in the water.

With that said, there’s an exception to the rule. Bromine dissipates faster than chlorine under the sunlight. Ultraviolet rays from the sun split bromine molecules into bromine atoms, resulting in the loss of bromine effectiveness as a sanitizer.

Moreover, stabilizers, such as cyanuric acid, are ineffective at protecting bromine, which adds to its vulnerability under the sun.

Chlorine, on the other hand, can nearly triple its longevity with the help of stabilizers.

For these reasons, you’d want to use a cover if you have an outdoor hot tub. Otherwise, you’ll end up spending a lot more money on continually replenishing bromine for your hot tub.

How much to use

The size of your hot tub will determine the correct amount of chemicals needed to sanitize. The first step is to measure the chemical levels in your hot tub precisely using a test kit.


In general, you want to keep the bromine level at around 3 to 5 parts per million (ppm) to keep your hot tub sanitized. Your bromine requirement will vary, depending on your bathing habits and how frequently you use your hot tubs.

When sanitizing the freshwater, you’ll want to add about 40 grams of bromine granules per 1,000 liters of water. Let the level fall to 3 to 5 mg per liter before using the hot tub.

If you have bromine tablets, you will want to add 1 tablet per approximately 100 gallons of water. You can dispense your bromine tablet using a floating feeder. You can also use an automatic brominator if you have one installed for your hot tub.

Don’t forget to read your bromine product’s labels to accurately figure out the proper dosage for your hot tub.


Your hot tub should maintain a chlorine level of around 1.5 to 3 ppm. You want to ensure the chlorine level doesn’t exceed 5 ppm. Or else, your hot tub water can irritate your skin, eyes, and respiratory system.

Generally speaking, adding about 1 teaspoon of chlorine per 100 gallons of water will sufficiently raise the chlorine level in your tub. Be sure to pre-dilute the chlorine with water in a container before pouring it into your tub.

To conclude, you will normally need to add more bromine than chlorine for the same level of sanitization. This is due to the slow-reacting nature of bromine.

Although chlorine is cheaper than bromine, bromine lasts longer, which may offset its high price.

How safe are they for your body?


Bromine doesn’t pose serious health risks for the most part. But in high doses, it can become a source of irritation.

Moreover, the bromine floater can cause problems, such as disruption of pH balance and damage to the hot tub surface, if left in the hot tub for a prolonged time.

Some people believe that overexposure to bromine can lead to hypothyroidism and toxicity. However, it’s not something that should concern you with the amount of bromine you’d typically use in a hot tub.

With that said, some people who are particularly sensitive to bromine. If you happen to be one of them, you’d want to be careful not to use an excessive amount in your tub.


It’s not as safe to apply liquid chlorine to your hot tub as it is for a swimming pool. This is mostly due to a difference in the volume of water and temperatures.

A typical pool has a much larger volume than hot tubs and can handle chlorine better, which means it’s a lot easier to over-chlorinate hot tubs than swimming pools.

A high temperature in hot tubs will readily dissolve chlorine molecules and rapidly disperse them. This, however, often results in uneven distribution of chlorine throughout your hot tub.

So, a certain area of your hot tub may have an extremely high chlorine level, which can be dangerous.

Furthermore, stabilizers (cyanuric acid) aren’t exactly welcomed in a hot tub since they can disrupt the balance in pH and alkalinity. As a result, you may end up having to spend unnecessary time and effort restoring the balance for your tub.

Overall, bromine tends to be a better option than chlorine for sanitizing hot tubs and indoor pools where the water isn’t exposed to sunlight.

Bromine vs. Chlorine: Advantages


  • It’s more effective at higher pH compared to chlorine.
  • Unlike chloramines, bromamines don’t gas off the water surface.
  • It’s possible to revive bromine using shock.
  • Bromamines still preserve their effectiveness as sanitizers.
  • Bromine withstands higher temperatures better, making it more suitable for hot tubs.


  • Chlorine reacts faster than bromine.
  • It costs a lot less than bromine.
  • It’s possible to increase the lifespan of chlorine using stabilizers.
  • It’s a better sanitizer for outdoor swimming pools.


There are a few things you need to keep in mind when handling these chemicals. 

  1. You need to store bromine and chlorine away from each other. If you store them near each other, the chemicals may react together, resulting in combustion.
  2. Make sure you use a different feeder for each. You don’t want any reactions between chemicals.
  3. You don’t want to combine bromine and chlorine in a dry state, nor mix the two chemicals in the water. 

Switching from one sanitizer to another

You need to keep a few things in mind if you want to change to a different sanitizing chemical from the existing one in your hot tub.

Switching from chlorine to bromine is a straightforward process. You need to discontinue using chlorine and start using bromine. In case you were using a feeder to dispense chlorine tablet, you’ll want to change to a new feeder for the reason we discussed in the previous section.

If you are shifting from bromine to chlorine, you need to drain your hot tub and flush the line before introducing the chlorine into your hot tub. This is because any leftover bromide ions can react with your chlorine sanitizers to turn them into bromine.

So, you want to ensure that your hot tub is completely clear of any bromide ions before adding chlorine.

How to add chlorine and bromine tablets into your hot tub

  1. Add a bromine tablet into a feeder to maintain the bromine level in your tub
  2. Adjust the feeder If it allows you to control the rate at which it dispenses bromine. Read the directions on the labels to determine the ideal rate.
  3. Let the feeder dispense bromine throughout your tub and continue to monitor the bromine level.


Both bromine and chlorine are effective disinfectants for water, but one tends to be better than another in different settings.

Bromine’s characteristic makes it an ideal chemical for treating hot tubs, while chlorine serves as the most effective sanitizer for swimming pools.

If you take anything away from this article, let it be this: safety always comes first when handling chemicals.

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