Select Page

If you’re wondering where to add chlorine or bromine to your pool or spa, you’re in the right place. The truth is spa sanitizers and pool sanitizers are only slightly different compounds.  

While bromine is more stable, chlorine is more fast acting. Both are effective water sanitizers and affordable pool chemicals. But bromine is better for the hot water temperature in spas, and chlorine is better for pool owners.

We’ll help you learn all you need about chlorine and bromine and which is right for you!

What Are the Main Differences Between Bromine and Chlorine? 

Both chlorine and bromine are part of the halogen family of compounds. Halogens are the compound that makes up the different varieties of salts around the world. Halogens also create more common sodium compounds like sea salt and everyday table salt.

Without halogens, salts like sodium bromide and sodium chloride would not form. Halogens are highly reactive with metals which is how the sodium molecules form. Bromine and chlorine are both halogens but have slightly different chemical compositions.

Distinctive characteristics of bromine include:

  • Reddish rust color in its natural state
  • Has an atomic number of 35
  • Code Br on the periodic table
  • Naturally, in a liquid state
  • Ionizes particles in the water
  • Has six oxidation states
  • Electronegativity of 2.96

Distinctive characteristics of chlorine include:

  • Has a greenish color in a natural state
  • Has an atomic number of 17
  • Code Cl on the periodic table
  • Has eight oxidation states
  • Oxidizes particles in the water
  • Electronegativity of 3.16

Regarding pool maintenance, bromine and chlorine differ in their use and application to the water. Chlorine and bromine both sanitize and alter water chemistry, but they react differently to molecules in the water.

Chlorine is more susceptible to heat and the sun’s UV rays than bromine. Bromine is more stable than chlorine but slower acting. Since bomine works slower than chlorine, it’s a good longer-term water sanitizer.

Chlorine works faster than bromine and breaks down water particles quickly. However, chlorine is much less stable and requires additional chemicals to prevent it from dissipating in the heat and sun.

If you’re wondering whether you should use chlorine versus bromine depends on your individual pool needs. Indoor and outdoor pools, for example, have different maintenance needs, and you should choose the sanitizer that suits your needs best.

What Exactly Does Chlorine Do in Swimming Pools? 

Chlorine treatments kill bacteria through an oxidation process. It cleanses the molecular structure of bacteria, algae, and oils in the water. Once the chlorine and bacteria come together, the oxidation process creates a compound known as chloramines.

Chloramines result from the reaction between your pool water bacteria and the sanitizer. If your pool has a potent chlorine smell, it actually means your free chlorine levels are imbalanced.

Chlorine is a gas at room temperature and needs to be compressed into chlorine tablets or granular additives. When the chlorine is properly balanced, this reaction cleans the water, making it clear and safe for swimming.

What Exactly Does Bromine Do in Swimming Pools? 

Bromine treatments kill bacteria through a process called ionization. Ionization causes the bacteria and particles in the water to break apart at the molecular structure.

Bromine is an effective form of pool sanitation since it clears and purifies the water. Bromine is a liquid substance at room temperature, unlike chlorine. Manufactuers must compress chlorine tablets so the chemical stays at room temperature.

This liquid state makes bromine less reactive and more stable in swimming pools. However, it also makes it a slower reactor, which is not the best choice for quick sanitation of dirty water.

What Are the Benefits of Using Bromine in a Swimming Pool? 

Bromine has a slower chemical reaction than chlorine. This might seem like a downside, but it is more effective for long-term pool care.

Bromine also causes less skin irritation than chlorine and is better for people with sensitive skin. Bromine is the best choice if you or your guests have sensitive skin or are prone to breakouts.

Bromine is also a better choice for spas or hot tubs. Bromine is more temperature-resistant and doesn’t break down like chlorine in warm or hot water. Chlorine won’t last long in the hot temperatures of spa water and thus won’t properly sanitize it.

Bromine also won’t offset your pool water chemistry the way chlorine will since it has a lower pH. Since chlorine has a pH level of 13, adding it to your pool or spa water can seriously impact the pH and alkalinity. Bromine has a lower pH and alkalinity, so it’s much closer to a neutral pH level.

What Are the Benefits of Using Chlorine in a Swimming Pool?

The main benefit of chlorine in your swimming pool water is it’s an effective sanitizer. It’s highly reactive and fast-acting, making it the perfect option for cleaning bacteria and algae out of a dirty swimming pool.

Pools and hot tubs can be breeding grounds for bacteria, like E. Coli, and harmful parasites. Swimming in a pool with dirty and unsanitary water can cause diarrhea and digestive discomfort.

Chlorine kills these germs quickly and clears cloudy or green pool water. Pool owners can also add chlorine-based shock treatments to kill high volumes of bacteria, algae, and bodily fluids.

Shock treatments are highly concentrated chlorine solutions used to clean pools where the water is overly contaminated. Chlorine-based shock is the most effective thanks to how the chlorine binds with elements and kills the molecular bonds of these pollutants.

Which is Best to Use in a Hot Tub? 

Bromine is the best option for hot tubs because it’s more stable in hot water temperatures. Chlorine tablets dissolve quickly in the water when it’s very hot, which doesn’t give the chemical enough time to kill germs.

You can use chlorine tablets, liquid chlorine, or granular chlorine in a hot tub. But it won’t last as long. Even though bromine costs more than pool chlorine tablets, it will cost much less over the long run.


Pool owners and spa owners have several options when selecting the right water sanitizer. However, chlorine and bromine have different uses and applications. If you own a pool or spa, then chlorine and bromine are best for balancing the water.

Since spas, hot tubs, and jacuzzis all have higher temperatures, bromine is the better option. Even though bromine isn’t resistant to UV rays, it’s more resistant to heat. Chlorine molecules break down much faster and aren’t ideal for use in a pool or spa.

We made a complete guide on maintaining a hot tub for all the new hot tub owners, so check it out today!


Should You Use a Stabilizer with Bromine? 

You don’t need to use stabilizers with bromine in a hot tub. Bromine is more stable than chlorine in hot water temperatures and won’t dissipate like chlorine will. There aren’t any known effective stabilizers for bromine which is why it’s better for spas with covers or indoor jacuzzis.

Are Chlorine Tablets Better Than Liquid Chlorine?

There isn’t really a preference or better option when it comes to choosing a type of chlorine. Chlorine tablets are better choices to lower your pool’s pH and acidity. However, liquid chlorine is usually better if you don’t want to raise or lower the pH of your swimming pool.

Does Bromine Come in Liquid Form?

Bromine is usually distributed in liquid form. Bromine stays in liquid at room temperature but can be sold in powder and granular form.

How Do You Add Bromine to Your Swimming Pool? 

The amount of bromine you add to your pool depends on your current levels and the size of your pool. Pool owners should add bromine to their pool as soon as the levels drop below three parts per million.

Most pool bromine should be added as pellets to the water since this is the most common form of bromine sold. However, we don’t recommend using bromine in outdoor pools because it’s impossible to stabilize and will likely need to be replaced constantly.

How Do You Add Bromine to Hot Tubs?

Bromine is the best option for sanitizing spa water and jacuzzis. You can add bromine as a tablet, granular, or liquid compound to hot tubs.

Start by shocking your spa or hot tub to sanitize the water. Don’t use chlorinated shock, though, since this will likely react with the bromine. Finally, measure the bromine and add it gradually to the water.

Test your spa or hot tub water as you add bromine to ensure it doesn’t get too high.

What Are the Appropriate Bromine and Chlorine Levels?

The appropriate amount of chlorine and bromine in a pool is 4-6 parts per million (ppm). The appropriate chlorine and bromine levels in a hot tub are between 1-3 parts per million (ppm).