Bromine vs. Chlorine: What’s Best for Your Pool

Written by Michael Dean
February 7, 2024

bromine and chlorine on periodic table

Sanitizing your pool or hot tub is crucial to prevent the nasty growth of algae or bacteria. Most pool owners use chlorine as the primary sanitizing agent. But you may be surprised to hear that there is another alternative that most people have not even heard of.

Bromine is another chemical comparable to chlorine in its effectiveness at sanitizing pools. In this article, I will compare the two chemicals and help you decide which one works best for you.

Main Takeaways

  • Bromine has many uses and is a preferred chemical for many spa pool owners as it works better under warm temperatures, but it is affected more by UV rays than chlorine.
  • Chlorine needs to be replaced more often than bromine.
  • If switching chemicals, drain and thoroughly clean the pool first.
  • Bromine costs twice as much as chlorine.

How They Work

Let’s start with basic overviews for each chemical and how they fit into your basic pool chemistry.


Chlorine is a natural chemical element scattered over the globe, primarily concentrated in salty oceans. It’s a critical nutrient for animals and plants.

Chlorine is used to clean drinking water because it kills pathogens by destroying chemical bonds in contaminants.

When chlorine confronts enzymes, a chemical reaction occurs, causing the molecule to fall apart or change shape. This causes the bacteria to be destroyed.


Like chlorine, bromine is another naturally occurring element. At room temperature, it becomes a liquid. It dissolves in water with a bleach-like odor.

One significant difference between chlorine and bromine is you would not use bromine to sanitize drinking or cooking water.

There are plenty of uses for bromine. It’s an oxidizer, pool sanitizer, and algaecide. Many spa, pool, and hot tub owners use bromine instead of chlorine. One of the main reasons is that bromine works better under warm temperatures than chlorine.

Effectiveness Comparison

In this section, I look at how well each chemical works.


Disturbing as it may sound, the water we drink is constantly exposed to everything from bacteria and parasites to mold and viruses. These contaminants build on water mains and in storage tanks.

Chlorine eliminates the bacteria, algae, and other pollutants that grow in our water systems. The EPA has set regulations for treating water with chlorine to kill germs that may reach our taps.

This is why many pool techs and owners turn to chlorine. When a chlorine molecule binds with contaminants, you can no longer use it for sanitation, so chlorine must constantly be replaced in pools.


Bromine neutralizes harmful pollutants in water. It does so continuously and for significant amounts of time. This is a great advantage over chlorine as bromine does not need to be added as often to disinfect.

Stability Comparison

A stable sanitizer is safer to use. Is chlorine or bromine more stable? Let’s find out.


Chlorine is a safe chemical that keeps us healthy by killing germs in the water. But misusing chlorine can be risky. Do not mix chlorine with other chemicals. Compounds created from mixing chlorine will create toxic vapors.

Chlorine developed for pools and spas protects us from germs. It’s effective against health conditions like diarrhea or swimmer’s ear. The CDC says pH and chlorine constitute the first line of defense against contaminated waters.


Bromine remains stable at higher temperatures than chlorine, which is why it is popular in hot tubs. The chemical composition of bromine reacts differently than chlorine and cleans water more efficiently in hot temperatures.

It is worth noting that bromine will deplete in UV rays more rapidly than chlorine due to the product having little UV protection.

How Much To Use

How much should you use to disinfect your pool? The answer is a bit different for chlorine and bromine.


You should maintain between one and three ppm (parts per million) in your pool. Determine the number of gallons in the pool and multiply it by 0.00013 ounces per gallon to know how much chlorine to use.

Always remember to test your water before adding chlorine. Use a test strip to test the current chlorine level. Too much chlorine increases the harmful effects of the chemical. It can also generate gasses as the water evaporates. The gasses can cause severe discomfort in the eyes and nose.


Like chlorine, I also recommend shooting for three to five ppm for bromine. Bromine is popular for withstanding greater temperatures than chlorine; it’s not surprising it’s the preferred sanitizer for hot tubs and spas. Compared to bromine, chlorine requires much more maintenance. Bromine also has a greater efficiency over a wider pH range than chlorine. You can sometimes add too much, though. Read my article on how to lower bromine levels if that’s the case for you.

Cost Comparison of Bromine vs. Chlorine

One of the main reasons most pool owners opt for chlorine as a sanitation product over bromine is the cost. Bromine is a much more expensive product, and pool owners can expect to pay up to double the cost of chlorine for it. For example, a 50-pound bucket of chlorine will usually cost around $150, while a 50-pound bucket of bromine will cost about $300.

Chlorine vs. Bromine: Health Concerns

As long as you use these elements in proper amounts, both bromine and chlorine are considered safe.

Chlorine can create difficulty breathing, sore throat, wheezing, coughing, chest tightness, eye and skin irritation, and other conditions. Most conditions result from ingesting heavy amounts of chlorine into the body, which you’re likely at low risk of in a pool.

Chlorine also contains bleach, has a distinct smell, and can irritate the skin. On the other hand, bromine is widely known for having an imperceptible odor. Pool water treated with bromine has fewer bad eye or skin reaction reports. And since bromine has no bleach, water has less effect on clothes.

Bromine has a long shelf life and dissolves slowly. In some applications, it’s activated with an oxidator. The solution will last longer than chlorine.

If your water is outdoors, you’ll need a cover as bromine has no defenses against UV light. UV light kills bromine faster than it does chlorine.

When not used safely, breathing in bromine gas can give you a headache, watery eyes, and irritate mucous membranes. Getting bromine gas or liquid on the skin can cause irritation and even burns.

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How to Use Chlorine and Bromine Granules (And Some Safety Tips)

PPE required:

  • Goggles
  • Gloves
  • Full cover clothing
  • Respiratory mask

Fill a container or bucket halfway with warm water. I suggest you use water from the pool, spa, or hot tub. Depending on the size of your swimming pool, add one to two pounds of granules to the water. Stir it with a stick. It’s best to use wood for chlorine, as any other material will get bleached.

The pump has to circulate the mixture. Otherwise, it will settle on the pool floor. Turn on the pump and remove the skimmer cover. Slowly add the chlorine mixture to the skimmer to avoid spillage. Put the skimmer cover back. Don’t use the pool for a few hours, so the chlorine disperses sufficiently.

For a bromine pool, turn on the pump and remove the cover. Soak the filters overnight with a filter cleaner. In the meantime, get to work with your granules.

Fill your hot tube with fresh water. Check the pH for balance. You can add 60 grams of bromine granules for every 2.5 gallons of water. Wait for the level to drop to between three to five milligrams per liter before getting into the tub. Bromine fumes can cause headaches and difficulty breathing, so make sure to wear a respirator.

Both chlorine and bromine can cause skin irritation if the concentrated chemical comes into contact with your skin. This is why I recommend wearing full-cover clothing and gloves. Take a look at my guide on swimming pool chemical storage for storage and handling.

How to Use Chlorine and Bromine Tablets

To safely use tablets, you need to know the volume of your pool. Use my pool volume calculator to get an estimate. Round your volume up to the nearest five-thousandth gallon. So, if your rounded number is 10,000 gallons, you’d use two chlorine tablets (These estimates are for three-inch tablets; visit my research on the best pool chlorine tablets for recommendations).

For bromine pools, you want to manage levels of bromine residue of two to three ppm at all times. Use three tablets for every 300 gallons for your spa or hot tub. The best way to do this is with an automatic brominator or floating tablet feeder. Apply your bromine tablet treatment at least once a week. For pools, add at least 17 tablets for every 10,000 gallons of water or as needed.

Hayward CL200 In-line Automatic Chemical Feeder

Hayward makes a great basic automatic chemical feeder that I recommend for most pool owners.

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U.S. Pool Supply Pool Floating Tablet Chemical Dispenser

This affordable dispenser from U.S. Pool Supply can dispense 3" chlorine or bromine tablets.

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Can You Switch From Chlorine to Bromine (or vice versa)?

If you are using a chlorine hot tub or swimming pool and have decided to switch to bromine or the other way around, there are a few quick steps to take, as mixing the two chemicals in your pool can cause a hazardous reaction.

You must drain the pool entirely if you plan to switch chemicals. This may be an expensive and time-consuming chore, but it must be done to prevent disaster.

After the pool is completely drained, clean the surfaces of the pool thoroughly, rinse down the pool, allow it to dry, and finally, refill the pool and add the new chemical.

Bottom Line

No one wants to sit in a tub of pollutants. Pool sanitation will be instrumental in cleaning your water. When looking at chlorine versus bromine, use information like the material above to know what’s best for your pool.

Questions on this topic? Drop me a line; always happy to help.

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