Whether you’re a veteran pool/spa owner or a newbie to all things pool-related, you’ve probably heard of chlorine and its use as a water sanitizer. But have you heard of bromine?

What are the differences between bromine and chlorine? Which is a better choice to disinfect your pool or spa? 

Don’t worry, there won’t be a quiz today. Instead, we’ll answer those questions and more to help you make the most informed decision about how to keep your pool and spa sparkling clean! 

Bromine and Chlorine Explained

Bromine is far less common, but actually very similar to chlorine in a lot of ways with its own unique benefits. It is also used to sanitize pools and spas as an alternative to chlorine.

What They Are

Chlorine and Bromine are both chemicals that are situated very near each other on the Periodic Table of Elements. As Halogens, they can be very dangerous in their elemental state. Luckily, the versions we use to clean our pools and spas are actually chemical compounds.

Since Bromine is far too reactive to exist as a free element in nature, it’s more commonly found in two compounds: sodium bromide (NaBr) and potassium bromide (KBr) which are found in seawater.

What Physical Form They Come In

Chlorine comes in several different forms: tablets, sticks, and in a dry granular state. The most popular version by far is chlorine tablets. These dissolve slowly in your pool or spa in a floating or automatic feeder, making them the most low-maintenance option.

If you opt to clean your pool with bromine, you’re going to find that it’s pretty similar to how you would add chlorine. Bromine comes in tablets and granules too and can be dispersed in much the same way. 

The consensus amongst pool experts (ahem) is that bromine is best added through a floating dispenser in tablet form. It does, however, require its own feeder that may add to the initial cost of doing business.

The Key Differences Between Bromine & Chlorine

Both chlorine and bromine kill bacteria and decontaminate your pool and spa water and they do it in similar ways. The two major differences between these chemicals are: how they affect people physically and how they react to higher water temperatures. And on that cliffhanger…

How They Work

When you add chlorine to your pool or spa, the chlorine molecules go to work right away attacking contaminants through a process called oxidation. This means that the chlorine literally steals electrons from whatever gunk happens to be in your pool, changing its molecular structure.

Through this chemical reaction, chlorine leaves behind a waste product called chloramines. If you ever wondered where the stinky chlorine smell the chemical is known for comes from, now you know. Chloramines are what cause swimmers the itchy, dry skin and stinky smell that we generally associate with the chemical itself.

Bromine, on the other hand, works by a process called ionization. It’s the same basic idea: bromine combines with bacteria but actually forces apart the chemical bonds of its adversary. Bromine also has a lower pH than chlorine, so balancing your water chemistry is going to be a breeze using this sanitizing method.

The difference here is that once chlorine has done its job, the waste it leaves behind (chloramines) actually decrease chlorine’s overall effectiveness. It’s used up, burned off, and… it’s gone. Whereas even after bromine has sanitized the water, it is still active and continues to work, without the smelly aftereffects.

How Much You Need to Use

Another important difference is the amount of each chemical required to do the same job. As a result of the chemical processes of each, the bottom line is that less bromine is needed to sanitize the same amount of water.

No matter what we tell you here, it’s important that you always consult the manufacturer’s instructions before adding anything to your pool or spa. Chemical formulations are different and each pool/spa has its own specifications. Once you’ve followed the guidelines and tested the water, you’ll be able to decide if more disinfectant is necessary.

Chlorine: 1-3 ppm (parts per million)

Bromine: 3-5 ppm (parts per million)

A good rule of thumb is to always aim for the higher end of the spectrum with each chemical. Although it looks like you need to use more bromine than chlorine to get the same outcome, the reality is that you don’t have to add bromine to your pool or spa as often. So… it evens out.

How Quickly They Kill

Chlorine is a fast-acting chemical. It rips through the gunk in your pool very quickly and then is done. Bromine, although highly-reactive, is a little bit more laid back than chlorine. It works more slowly but works longer than chlorine. 

It’s like the Tortoise & the Hare fable. Both are going to get to the finish line but they’ll do so at their own pace.

How Long They Work

As we mentioned above, chlorine works faster but for a shorter period of time while bromine works longer at a slower pace. The big difference between chlorine and bromine here is going to be how they act in warm water. 

If you’re a spa owner, make sure you take notes here. Bromine is a lot more stable than chlorine (obviously, because of how it functions more slowly) but especially so in warm water. This is one of the major reasons that bromine is primarily used in spas, whereas chlorine is used in swimming pools. 

But… here’s where one big exception comes in. Bromine is more stable than chlorine except when it comes to UV light. The radiation from the sun destroys both chemicals without mercy, but bromine breaks down more quickly here. This is why if you’re using bromine in your spa or hot tub, it’s a really good idea to keep your cover on it during the day.

You spend your hard-earned money on these chemicals and you want them to break down while doing their job of decontaminating your pool/spa water. You don’t want them breaking down early due to water temperature or UV radiation from the sun.

How People React to Them

The good news is that if you’re using these chemicals in their correct quantities and according to manufacturer guidelines, they are completely safe for humans. You’re waiting for the catch, right? Well there is one and that is that everyone reacts to things differently. 

For example, I have never been able to open my eyes underwater in the pool — no matter what pool I was in. My eyes are super-sensitive and it was just too painful for me to do. Needless to say, I was always jealous of my friends who could. 

Chlorine can be particularly harsh, especially for people with sensitive skin and/or eyes (me) and to those with asthma or other breathing conditions. When the chlorine in your pool is doing what it’s supposed to, the byproduct produced (chloramines) can wreak havoc on your skin, discolor your hair, and fade the colors of your new swimsuit.

Bromine is a great alternative for people with chlorine sensitivities as it tends to be gentler on the skin. It is much less abrasive than chlorine, its odor is not as strong and chemical-smelling, and it doesn’t have the same likelihood of triggering asthma attacks from the chloramines hovering in the air above the water.

The only major drawback to bromine is that it does leave a lingering chemical smell on your skin that is much more difficult to scrub off than chlorine. Bromine is definitely a great option for people with sensitivities… but it is still chlorine-based, so if you or someone you know is actually allergic to chlorine, bromine is not going to be a safe alternative.

How Much They Cost

Okay, here’s where we get to it. The main reason that bromine isn’t used nearly as much as chlorine is the cost. Depending on where you buy, it can cost anywhere from a few bucks more to (possibly) double the price of chlorine. 

The cost is generally what stops many pool owners from using it in their pools, while spa owners might go with the bromine. You don’t need nearly as much chemical for a spa as you do for a pool. 

The equipment required for bromine is going to cost a bit more too. Bromine requires a floating feeder or cartridge system to function properly. It’s more complicated than chlorine so the learning curve can sometimes scare pool/spa owners away from giving it a try.

But it’s important to consider the cost-effective features of bromine.

Bromine doesn’t clean-and-run like chlorine. It keeps working a lot longer with the same amount of chemical, its lower pH will help keep your water balanced more effectively, and it’s much more stable in higher heat, making it a great choice for hot tubs. All of these factors may contribute to the costs actually evening out a bit.

So, Which One Should You Use?

In the end, it all comes down to personal preference and how your pool or spa is situated.

  • On a budget? Go with the chlorine.
  • Have sensitive skin and/or asthma? Give bromine a try.
  • Live in a very warm climate? Bromine might be a good option.
  • No shade in your backyard? Chlorine is probably a good choice.

Conclusion

Hopefully you now have a better idea about your options when it comes to pool and spa sanitizers. Whichever method you choose, it’s important to remember the foundations of pool maintenance and keep your levels where they need to be and your water balanced.

A sparkling clean pool or spa filled with healthy swimmers and soakers is the goal.