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Chlorine vs. Bromine: What’s the Difference?

chlorine vs bromine

Whether you’re a brand new pool owner or seasoned pro, chances are you have heard about chlorine. The powerful water sanitizer is synonymous with pools and swimming, but have you heard about its cousin, bromine? This lesser known sanitizer is similar to chlorine, but with a few key differences. In this post, we will discuss the chlorine vs. bromine debate, and help you decide which sanitizer is best for your pool or spa!

Chlorine vs. Bromine

First things first, let’s cover the basics. Chlorine and bromine are sanitizers that help keep your pool or spa water clean and safe. Both chlorine and bromine come in tablet and granular form, while chlorine is also available in liquid form.

Understanding how each sanitizer works is key to deciding which one is the best option for your pool or spa. While both chlorine and bromine clean your pool, they do so in different ways. Let’s dive into the differences between chlorine and bromine, and discuss the unique role of each sanitizer.

How Chlorine Sanitizes Your Pool or Spa

in the swim 3 inch chlorine tabs

As many pool owners know, chlorine is what is known as an oxidizing sanitizer. When chlorine is added to your pool water, it immediately zeroes in on contaminants and neutralizes them through oxidation. During this process, chlorine molecules penetrate the contaminant and strip the electron particles, breaking down the contaminant. Following the oxidation process, waste byproducts called chloramines are leftover.

Chloramines create the unpleasant, overwhelming chemical smell and skin irritation commonly associated with chlorine. The production of chloramines is the biggest inconvenience when using a chlorine sanitizer. Many people assume the intense smell of chlorine means their pool is clean, but in reality, it means the opposite. As chloramines build up over time, they decrease the amount of Free Available Chlorine — the active, sanitizing molecules — and leave your water unprotected. The only way to clear the chloramines is to shock your pool, also known as reaching breakpoint chlorination. When your pool hits breakpoint chlorination, the chlorine levels exceed the contaminant or oxidant demand, and Free Available Chlorine starts to increase.

Chlorine is available in tablets — the most common form — sticks, and granules. Tablets and sticks work well in floating dispensers, and in-line or off-line chlorinators. Granular chlorine needs to be pre-dissolved in a bucket of water before being dispersed throughout the pool.

Ideal Chlorine Levels: 

  • Pool: 2.0–4.0 ppm
  • Spa: 2.0–5.0 ppm

How Bromine Sanitizes Your Pool or Spa

in the swim brominating tablets

While chlorine oxidizes contaminants to get rid of them, bromine eliminates contaminants through ionization. During ionization, bromine particles attack and break apart the pollutant molecules. But unlike the ineffective and frustrating chloramines left over after chlorine oxidation, bromine produces bromamine molecules that continue to sanitize the water after ionization. Chlorine-free pool shock will reactivate the bromamine molecules, returning them to their full strength.

Bromine is more limited than chlorine regarding the forms it comes in and how it’s distributed in your pool. Bromine is only available in tablet and granular form, and works best in a floating dispenser. Because bromine tablets take longer to dissolve than chlorine tablets, they don’t work well in in-line or off-line chlorinators.

Due to its slow-dissolving nature, bromine takes longer to build up a residual in the water, and is difficult to raise quickly if the level drops. A bromine booster is a great product to use if your bromine levels drop suddenly or you need to raise them quickly. Bromine boosters instantly build a bromine residual in your pool or spa.

Ideal Bromine Levels: 

  • Pool: 2.0–4.0 ppm
  • Spa: 4.0–6.0 ppm

Which Sanitizer is Better: Chlorine or Bromine?

The answer to which sanitizer is best depends on whether you’re sanitizing an indoor or outdoor spa or pool. Chlorine and bromine are both effective sanitizers, but each one has its own optimal working conditions, and its own pros and cons.

Advantages of Chlorine

  1. Typically half the cost of bromine sanitizers.
  2. Compatibility with Cyanuric Acid (stabilizer/conditioner) protects it against UV evaporation.
  3. Sanitizes water faster than bromine.
  4. It’s both an oxidizer and a sanitizer.
  5. Easier to quickly raise or lower levels.

Advantages of Bromine

  1. Stays effective at higher pH levels.
  2. Remains stable in warmer water.
  3. Can be reactivated or re-used by adding an oxidizing shock.
  4. Bromamines retain killing power, chloramines do not.
  5. Bromamines do not gas off the water surface, as chloramines do.
  6. Often less-irritating to people with sensitive skin and eyes.

Frequently Asked Questions

Below are a few commonly asked questions regarding caring for a bromine pool and what type of pool it is best suited for.

Can You Shock a Bromine Pool?

You can shock a bromine pool with non-chlorine shock or chlorine shock. Shocking a bromine pool oxidizes contaminants and creates bromamines, which aren’t harmful. Refer to the shock dosing instructions before adding shock to your bromine pool. The standard dose for a chlorine pool is typically sufficient for a bromine pool.

Can You Use Bromine in Outdoor Pools?

While bromine can be used in outdoor pools, we don’t recommend it because bromine is not compatible with Cyanuric Acid (CYA). CYA protects chlorine molecules from the sun and prevents evaporation. Therefore, Bromine is at a high risk for evaporation when used in outdoor pools.

Should You Use Bromine or Chlorine in Indoor Pools?

Use a bromine sanitizer for indoor pools that receive little sunlight. Bromamines, the leftover bromine particles, do not “gas-off” the surface of the water like chloramines. Chloramines are potentially harmful to metal structures like pool ladders, furniture, and any other metal when trapped indoors. Outdoor pools are better suited for handling chloramines because of the abundant airflow.

Switching Sanitizers

Perhaps the most important part of having a chlorine or bromine-based pool is knowing what to do if you want to switch sanitizers. Switching from chlorine to bromine is simple, while switching from bromine to chlorine is a laborious process.

Chlorine to Bromine

To switch from chlorine to bromine, simply stop using chlorine tablets, and begin using bromine tablets! Replace your chlorine floater or in/off-line chlorinator to prevent any chlorine residue from coming into contact with the bromine.

Bromine to Chlorine

chlorinator

Changing your pool’s sanitizer from bromine to chlorine is not quite as simple. Making this change requires a full pool drain to remove the build-up of bromine ions in the water — which will continue to convert added chlorine into bromine. Even when bromine levels are zero, there are still ions present, which is why draining is necessary. As with switching from chlorine to bromine, replace your existing floating chlorinator with a new one to avoid cross contamination.

There you have it — the ultimate guide for the chlorine vs. bromine sanitizer debate! Each sanitizer plays an important role in pool and spa care, and neither one is “better” than the other. The best sanitizer is the one that works for you and your pool.

65 thoughts on “Chlorine vs. Bromine: What’s the Difference?

  1. Switching a small spa from chlorine to bromine.
    Can I just get a new floater for putting the bromine in?

    • Yes, that’s right. Just start using bromine tablets. (not true the other way around, if it was formerly bromine, draining would be required). You should also add Bromide Booster, bromide ions that will help the bromine tablets to register on the test kit.

  2. I have a 275 gallon international bulk container that I can enclose to keep the sun from it. Would chlorine or bromine be best? It is used for cleaning and showers.

  3. Wanda Adams

    We purchased a galvanized metal stock tank (700 gallons) for a backyard pool, and I really don’t want to use chlorine. The tank will get some direct sun but is mostly covered by a shade sail. In your opinion, would bromine tablets in a brominater work for our setup?

    • Hi Wanda, sure you can use bromine, and non-chlorine shock. It will cost more to use bromine, because it’s more expensive and also because you can’t stabilize it, but it can be a good option. Give it a try!

  4. Lynn Edelstein

    Just moved to a house with an outdoor pool, so I’m a newby at pool maintenance. We are having lots of itchiness due to, I believe, the chlorine used in the pool. We live in Southern California, can we switch to Bromine? My mother has an outdoor pool in NY that we’ve swam in for many years and she uses Bromine. We never had itchiness, even days after swimming.

    • You can switch to bromine, no need to do anything, except replace the chlorinator with a brominator, which is different as bromine tabs need higher flow.

  5. Want to drop my hot tub down to 85 to use as a cool tub during summer. I use Bromine, will
    It still be affective in this lower temperature or should switch to chlorine for summer. I keep the spa covered when not in use so sunlight shouldn’t be an issue. Is there anything else I need to be aware of to keep the water clear when drop it to this lower temperature.

    • Dave, nothing at all, just continue like always, nothing different. 🙂

      • Bromine is fine at that temperature – people told me it better in 90+ range.

  6. Just setting up my hot tub and am now bromine tablets, previous years I was using chlorine tablets/pucks in a chlorine floater.

    I just threw the bromine in the same chlorine floater, but am now reading on your site this could cause a dangerous chemical reaction. I have take the bromine out of the floater and removed the floater from the hot tub.

    Do I have to drain the hot tub and flush it out now as well? I Just don’t know if this possible reaction would have put something dangerous in the water that’s not good for us.

    Thanks!

    • Hi Kelly, no need to drain the tub, now that you have removed the floater. Just buy a new one for the bromine.

      • Thanks for the help, one other question. I noticed the bromine tablets/pucks have brown spots and streaks in some of them. Is this normal or do I need new ones? Thanks, Kelly

        • Hello, not normal for bromine to have streaks and spots. Not sure what that could be. I would use them and if they seem effective, try to use them fast to rotate them out of stock. If you have more concerns about their use, contact the manuf, listed on the product pail.

  7. Ted Behrens

    Hi We have a new inflatable hot tub that holds 250 gallons. I have purchased Bromide tabs but wonder and a shocker solutions. Can you give me advice on what to add and how much for this small hot tub. Thanks!

    • Hi Ted, when you run a bromine hot tub, after refilling, add 1.5 ounce of bromide ions, normally sold as Brom Boost, or Sodium Bromide… this will boost the level of bromides in the water. Then use 3-6 1″ bromine tablets in a floater or feeder. You can then regenerate the bromide ions into bromine, by shocking the water. Spa shocking oxidizes and destroys all byproducts, waste, and other matter in the water to make it safer and easier to manage, but it also will reactivate bromides and turn them into bromine. You need very little shock to do this, for a 250 gal tub just 1.5 oz. of shock should be enough. You can use chlorine oxidizer like Spa 56, or use an MPS chlorine-free oxidizer like Renew or Sodium Dichlor. https://www.intheswim.com/c/sanitizing-spa-chemicals

  8. I have a bromine hot tub and a salt clorinator inground pool, I’m wandering if it is ok for us to go between these two or if there is any negative affects from doing so. Thanks in advance.

  9. Terri Cove

    We bought an 8ft diameter inflatable pool for our kids. It holds too much water to empty every night. I am trying to figure out what I should use to treat the water in the pool? We use bromine in our hot tub but was not sure that would work for their pool. I don’t want anything too harsh for the two young boys.

  10. We just purchased a home with a 25,000 gallon in-ground vinyl lined pool. We just had it opened but haven’t added any chemicals. It has been treated with chlorine in the past but I am wanting something that uses less chlorine so it’s easier on sensitive skin but I also want the pool to be clean and clear. There are so many different options out there! What would you recommend?

    • Hi Tammy, my #1 recommendation would be to use the Nature2 Express mineral purifier. Easy to install, low maintenance, and reduces your chlorine use by 50%, while at the same time making the pool look clearer, bluer and more sparkly.

  11. Mark BOLC

    Thanks Davy. Is the chlorine in the pacs any different than standard chlorine tabs? And what chlorine would you recommend for an inground liner pool?

  12. Mark BOLC

    I have a 35k gal inground vinyl pool and have been using the frog system to chlorinate. I’m getting close to opening and wondering if I should try a different sanitizing system this year. I would like to use less chlorine but want it to always be clean and safe for the kids. Cost is not an issue. What would you recommend

    • Hi Marc, I like the Frog system or the Nature2, both mineral purifiers. Using the Frog Bac-Pac for chlorination can be overly expensive however. If it was me, I would use the Frog system with the Mineral Reservoir, and then put chlorine tablets in a Pentair in-line chlorinator.

  13. We’ve had our in-ground chlorine pool for 13 years. We open it in April and the water temperature is 68ish degrees. It is in the direct sun and by early July, the water is 90+ degrees, and it eats up the Chlorine like crazy. Is it safe to switch from Chlorine to Bromine in the middle of a swim season? And if so, at what water temperature?

    • Hi, are you using cyanuric acid (aka Stabilizer) to protect the chlorine from the sun? We recommend 30-50 ppm. Bromine has no way to stabilize, or protect from the sun, and switching would cost much more money, not just because Bromine is nearly 2x the cost of chlorine, but because it cannot be stabilized. But you can switch to bromine at any time or temperature, but you may be better off with chlorine, well-stabilized. 🙂

  14. Egle Visciulyte

    Hello,

    Please help me!! We have never had a pool before and now I bought an 8″ aboveground pool, which is lovely, but I bought not realising, that I will have to maintain it, imagine….now the water in the pool is green and I have read so much about how to clean it, that my head started to spin around. I end up with buying eater filter, bromine tablets with dispenser and on it’s box says to start up with a dose of free chlorine so I bought stabilised chlorine granules and now feel completely lost. Please please can I use these granules to shock my pool (555 gallons) and then use bromine dispenser? Would it be better to dissolve these granules before shocking the pool? And what doses should I use? I Hope you will be able to help me becuse I feel absolutely hopeless…thanks in advance!!!

    • Hello, these small pools are quiet popular for the garden set, but yes they do require some maintenance and a constant chlorine level in the water, and daily filtering of 12-18 hrs per day. You CAN use the granules to shock the pool, but you only need to use about 2 oz. or about 1/4 cup. Seal the shock bag back up very tight to lock out moisture, bugs and dirt, and prevent spills, and store is safely by itself.

      It may be suggested that you empty the pool, then refill with fresh water and start over? That will be a lot easier than trying to restore it with chemicals and filtering, which can take a week or two sometimes, depending on how bad it looks. If you can see the bottom, you might be able to filter it out, but if not, I’d drain at least 1/2, or all of it if you can.

  15. Hi. What is the best way to test for bromine in our spa and indoor pool?

    • Hi Bill, liquid drop test kits are superior to test strips, such as the Taylor Deluxe test kit K-2005. Superior to that however, are the photometer test kits, that interpret the sample color from among 64 million colors, these include LaMotte ColorQ and LaMotte SpinTouch. Test Strips can be off by as much as 20%, I am told.

  16. John Conley

    What is the self life of Bromine that is in a sealed container stored in an outside pool house? Can it still be used after a couple of years?

    • Hi John, yes – tightly sealed to prevent moisture from getting in, bromine tabs can last 5 years or longer. Very hot outdoor temps can reduce strength somewhat, but not by much, when the lid is tight.

  17. Is there a benefit to adding Bromine to a swimming pool that has chlorine ?

    • HI Bill, nope – no benefit that I can think of, and it can cause some conflict – when you add bromine to a chlorine pool, the bromine builds up over time, creating a chlorine demand, and eventually turning it into a bromine pool. The opposite is true for a bromine pool – you can add chlorine to it, which will reactivate bromides into bromine, a good thing. But adding bromine to a chlorine pool – is best avoided.

  18. New pool owners. We made the mistake of putting Bromine tablets (1pak appeared to be 30? 1” tablets) also applied Shock directly to the pool water at same time.

    How much trouble have we caused?

    Suggestions for next steps to properly go forward from here?

    Thanks

    • Hi Dave, no problem there, unless you put the bromine in the chlorinator. With lots of chlorine residue, it could react, but maybe not. You can use bromine in the pool, or chlorine, and if you want to use chlorine tablets, just start using them, and remove the bromine if you want. Just don’t physically mix chlorine with bromine, dry or wet – but to have them in the pool, separate but together, is ok. Some pools use bromine to sanitizer, usually indoor pools or pools with very little sunshine.

  19. When using bromine what other chemicals should I be using in my 15K fresh water pool? What should their balances be?

    • Hi Greg, it’s the same as for chlorine pools – pH: 7.2-7.8, Alkalinity 80-120 ppm, Calcium Hardness 200-400 ppm. I was about to write …Stabilizer 30-50 ppm, but of course bromine can’t be stabilized (to protect from UV ray degradation). So there is that difference, but all else the same. When using bromine tablets, you will want to add a granular Bromide Ion to build up a bank of bromides, to use fewer tablets.

  20. Can I use chlorine based shock (like Cal-Hypo) to shock the pool if I use Bromine tablets in my feeder?

    • Davy Merino

      Hi David, yes you can – in fact, chlorine shock is often used to reactivate bromide ions, converting them into bromine – which in fact, is why bromine tablets contain a bit of chlorine… So yes, no problem there!

      • Destinie Renzo

        I have a Jacuzzi and it’s a lite tint of green I’ve got my pH balance and alkaline perfect but my bromine is white and it’s showing its supposed to be purple how do I fix that? Can I use chlorine to shock it real quick if I’m using the bromine?g

        • Hi, chlorine shock (or non-chlorine shock) can be used to reactivate bromides in spa water, converting them to bromine. Now, you have to have an active bank of bromide ions already in the water, for this to occur. Many people use Bromine Booster to raise the bromide ion count, and then shock with MPS (non-chlorine shock) to activate or turn them into bromine. In addition, some spas may need to also use bromine tablets in a floater, to help maintain a bromine residual, which should be 3-5 ppm (and quite purple in your test kit, yes).

  21. Tom Hines

    Thanks for your professional advice on pools and spas,,, I’m about to re-fill my spa, it’s been about 2 months and I always used bromine tablets and so far never had problems even as my spa is in doors and yes of course I use an small exhaust fan in the window. But I am thinking about trying chlorine tablets this time,, I use to have a large pool in Calif. and had not problems,,, of the only reason I drained my spa cause I was having a skin problem with all water,, (long story),,, thanks again,, Tom

    • Davy Merino

      Hi Tom, chlorine tablets contain cyanuric acid, which protects chlorine from the sun, not needed in spas, but as long as the water is drained every 3-4 months, it should not pose a problem of building to high levels. Bromine is superior for use in hot tubs for several reasons, but I understand the cost of bromine tablets is more than chlorine. Most hot tub owners that have a ‘chlorine spa’, are NOT using pool chlorine tablets however, they are using granular chlorine, such as Spa 56, to activate bromides in the water. After draining, they add bromides to boost the level, and then add a scoop of granular chlorine, to ‘activate’ the bromides, turning them into bromine. Another scoop is added every 4-7 days, depending on use and need.

  22. Richard Casavant

    Hi, I am changing my chlorine for bromine in my spaberry (125 gallons/470 liters.) Can I use the same test strips to test the bromine levels as I used to test the chlorine? After two days of bromine (dispenser closed down tight) the reading is in the purple or very high. I have removed the bromine tablets and allowed just one in the dispenser (still closed down tight). i will check again in a day. Are there special bromine test strips that measure BR, PH and Alkalinity?

    • Davy Merino

      Hi Rich, good question. Bromine is 2.5x heavier than chlorine, so when testing with a chlorine test kit, multiply the result by 2.5 to establish the equivalent bromine reading. There are Bromine test strips however, AquaChek “Red” is bromine (yellow is chlorine). Another thing about bromine, is that tablets work best when the spa has a ‘bank of bromide ions’ built up already. Many spa owners add a small amount of Bromide Ions ‘Brom Booster‘ to the spa after draining and refilling, to establish an initial level of bromide (which converts to bromine with a shock oxidizer), instead of waiting 2-4 weeks for it to build naturally, from bromine tablets.

  23. will using bromine cause heater core to break down faster than clorine tabs

    • Davy Merino

      Hi Roland, I would think the opposite, but it’s not usually bromine or chlorine that causes heat exchangers to break down. Salt pools with a copper heat exchanger can experience corrosion and galvanic problems and damage to gas pool heater cores or exchangers, and many salt pools opt for cupro-nickel heat exchangers for this reason. For non-salt pools, it’s generally a consistently low pH and alkalinity, combined with other water balance problems, that can strip out the copper, and wear thin the copper tubes, leading to pinhole leaks and failure. Very high lime and calcium content can clog heater tubes in some cases. But chlorine or bromine, kept at normal levels, pose no harm to copper heat exchangers.

  24. Debbie Klein

    Hi. I’m 63 years old. I’ve been a swimming pool swimmer my whole life. Never had a problem. All of a sudden in the past 3 years, whenever I go swimming in my pool, I get a rash all over my body. It’s terrible. It takes a few days then it goes away. IF I go in again, same thing happens. I havn’t gone in my pool in 2 years.I’m thinking I can’t take Chlorine any more. Any advice? Thanks.

    • Davy Merino

      Hi Debbie, I haven’t heard of chlorine giving people rashes, but if a pool had high levels of certain bacteria like pseudomonas, that will cause a rash. Or it could be from using someone elses towel or laying on an infected lounge chair. At my pool this summer, a bunch of divers all caught a red bumpy skin rash, and they all blamed the pool – turned out to be a ‘divers shami’ towel that they were sharing…

      • Hi, My daughter also breaks out in red bumps or chapped red areas on her face, regardless of the pool…. We are thinking it is a chemical reaction combined with the chlorine, and her sunblock. I once accused my husband of not putting sunblock on at all, because my daughter had small red blistery bumps on her face….I called a neighbor who verified none of the other swimmers had a problem that day… and she saw my husband applying sunblock to our daughter’s face several times during the day, we have tried every type of sunblock i can think of… We are thinking of getting a pool, but adding an AOP or ozone system and the use of bromine …. Do you think that type of system will help? Thanks so much…

        • Hi Tina, bromine is considered milder than chlorine, but depending on the person, a similar reaction may occur. AOP systems, or using an ozonator plus a mineral purifier (nature2 or frog), along with a large DE filter, and regular shocking with non-chlorine shock, can allow you to go chlorine free in most pools.

  25. Question,

    I have a galvanized stock tank that we’ve made a soaking tube out of (Thank you Pintrest!!). It’s 5′ round, would bromine or chlorine be better? How much should I use and how often? Pam

    • Davy Merino

      Hi Pam, I’ve heard of those pools, very popular now. I would use a chlorine floater, with 1-2 tablets at a time, or however many it takes to produce a constant and consistent chlorine level of 1-2 ppm, as tested by your test kit. Also immportant is to keep your pH level in the 7.2-7.6 range, using pH adjusters as needed (up or down) to keep pH within range. You can shock the pool periodically with 1/2 lb of Dichlor shock (Di-Zap is our brand). Bromine can also be used, but since the tub is outdoors, and if it gets sun, stabilized tablets and shock may be a better choice.

  26. George Gray

    Would bromine be better if frequent swimmers have psoriasis?

    • It may be, bromine is known to be ‘softer’ than chlorine, in regards to skin irritation. Psoriasis affects people differently from what i understand – chlorine or bromine may irritate psoriasis symptoms on some people, and not so much with others. I am not aware of any ‘skin studies’ however that could prove the point, but the general thought is that bromine is a bit gentler on skin, as compared to chlorine. (all else being equal)

  27. evelyn johnstone

    if I switch to bromine do I have to empty my hot tub and start with new water? you said I would need a new feeder due to chemical reaction caused by mixing both and this suggested to me I need to change water also that contains chlorine

    • Davy Merino

      Hi Evelyn, no need to drain if going from Chlorine to Bromine, but if going from Bromine to Chlorine, the pool (or spa) should be drained, to remove the bromide ions, which will continue to produce bromine. And as you mention, chlorine and bromine should never contact each other. If you were using a bromine feeder or floater, it should not be used for chlorine tablets (and vice-versa), as the residues in the feeder can react with the similar but very different chemical.

  28. Thanks for ironing out the facts on the differences between these two elements. I have always been unclear on the subject! Readers at my blog will really appreciate this post. I also have some great Bromine Slogan and Chlorine Slogans you may find interesting on my site. Let me know what you think!

  29. How to make learning chemistry "cool" this summer -

    […] What’s the difference between chlorine and bromine? – They’re both sanitizers, right? […]

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