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What’s the Difference Between Bromine and Chlorine?

My wife and I have owned 3 different hot tubs, but with our first, I still recall being confused and wondering what’s the difference between bromine and chlorine.

Bromine & chlorine are both sanitizers used to rid of bacteria or viruses in pools or hot tubs. But chlorine is less stable in hot water and while it dissolves faster, bromine lasts longer and requires less frequent applications. Bromine also tends to be better at killing bacteria and viruses but can be more expensive.

But there’s a lot more to know about hot tub chemicals and sanitizing the water.

So in this article, we’re diving deep into the bromine and chlorine specifically. We’ll examine what the key differences are and why you might want to use one over the other. (hint: the answer may be different for pools compared to hot tubs).

Let’s dive in!

Confused about hot tub chemicals and not sure which ones are the best?

I take the mystery out of it in a recent article. I explore not only which chemicals you need, but also which ones you don’t that can be a waste of money. But I also explore which chemicals are best for sensitive skin and how to avoid the dreaded hot tub rash.

So just click the link to read that now on my site.

What are bromine and chlorine?

Bromine and chlorine are what we use to sanitize the water in a hot tub or swimming pool.

You can find them at your local pool or spa supply place, but also places like Wal-Mart, Home Depot, and, of course, Amazon.

But most of us don’t have a clue what the difference between bromine or chlorine.

We know chlorine is what’s in bleach, but bromine is more of an unknown. So is one better than the other? Is one better for a pool compared to a hot tub? Do some people use both?

Today, we’re taking the mystery out of it.

Bromine is a chemical element. It has a chemical symbol of Br and its atomic number is 35.  Because it’s an element, that does mean it’s naturally occurring. You can find it in the earth’s crust and in seawater, according to the CDC.

Chlorine, on the other hand, is also a chemical element. It has the symbol of Cl and the atomic number of 17. Like bromine, it too is naturally occurring and found both on land and in seawater.

Bromine produces less of a chemical smell than chlorine. However, the smell it does have tends to be harder to wash off after you get out of a pool or hot tub treated with bromine.

When chlorine enters your water and starts to attack bacteria or viruses, most of the chlorine gets used up in that process, requiring more frequent water treatments.

Wheras bromine tends to stay in the water longer. But let’s get more into the effectiveness of bromine and chlorine below.

Is bromine more or less effective than chlorine?

Let’s start by comparing both chemicals and looking at their pros and cons:



Dissolves much more slowly than chlorine More popular and used more often
Much more stable than chlorine for high temperatures Available in liquid, powder, or for a feeder
Kills viruses and bacteria better than chlorine Cheaper than bromine
Far less irritating to the skin than chlorine You have to shock your tub more often
Remains in the water longer Disperses into the water faster than bromine
Can create cloudier water than using chlorine Better at killing algae

As you can see, there isn’t a clear winner here.

Both have strengths and weaknesses. That being said, I do think it may be clear to many which one is better for a pool and which is better for a hot tub.

Chlorine works by oxidizing the contaminants that get into your pool or hot tub. Bromine, by comparison, ionizes the contaminants. So they both do the same thing but in different ways.

Because bromine is more stable at high heat, it is better for hot tubs than chlorine. Even though chlorine is generally cheaper, because bromine stays in the water longer, you actually save money by not having to treat the water as often.

Why might you want to use chlorine in your hot tub instead of bromine?

  • If your hot tub is prone to algae
  • If you don’t want to wait long to use it after treating the water
  • To save money on the initial purchase

If you do use chlorine, just be away that it has a higher pH than bromine, so using chlorine will affect your pool or hot tub pH balance.

Which is better chlorine or bromine?

As we got into above, neither one is a clear winner.

They both have pros and cons and it isn’t a black and white choice as to which one to use. That being said, for me, I only use bromine in my hot tub. When we get around to getting a swimming pool, I will most likely use chlorine for that.

There are a few reasons for that, some of which I got into above.

But for starters, chlorine breaks down in high heat. I don’t set our hot tub at 104° like some do (I like it lower for our kids). But still, even 98° is enough to cause the chlorine to break down quickly.

So while it’s cheaper to buy, if I have to reapply twice as often, it sort of negates the initial savings.

Then there’s the matter of skin irritation. We have a toddler and 2 older girls and chlorine is naturally more of a skin irritant than bromine. In a pool where everyone is jumping, swimming, or horsing around, it’s different than just soaking in a hot tub.

I also like the fact that bromine is much better at killing bacteria and viruses than chlorine. After all, since hot tubs are just a few hundred gallons instead of the thousands in a pool, it’s an ideal setting for bacteria like legionella, which can lead to Legionnaires’ disease.

For a swimming pool, however, it’s worth noting that the sun’s UV light destroys bromine much faster than chlorine. That’s why most swimming pools use chlorine and most hot tubs use bromine.

As long as you keep your hot tub covered when not in use, the bromine will stay relatively protected from UV rays.

Since we all know chlorine is the main component in bleach, lots of pool and hot tub owners have wondered if you can use liquid bleach. I break it all down in a recent article, including the one way you should NEVER use bleach in your pool or hot tub.

So just click the link to see it now on my site.

Can you switch from chlorine to bromine in a hot tub?

Yes, most definitely.

I started off, before I knew much, using chlorine. Then later, once I got to know a little more, I switched us over to bromine.

Bromine and chlorine are 2 sides of the same coin and do the same basic task; sanitize and protect your water. Now, that’s not the same as shock which oxidizes your water. Shock also removes bromamines and chloramines which are a by-product of sanitizing your water.

Bromamines and chloramines are bad because they fool your test strips into thinking the water has the right amount of bromine or chlorine in it, when in fact, it may have none.

When you use a test strip and think everything’s OK and don’t add more bromine or chlorine, the water can become a high risk for bacteria or viruses.

Switching from chlorine to bromine or vice versa is simple, but requires draining when converting to chlorine.

In going from bromine to chlorine, you have to completely drain your pool or hot tub. If you don’t get rid of 99% of the water, the bromide salts which remain after bromine use, actually convert the chlorine to bromine; defeating the purpose of switching.

When going from chlorine to bromine, just start adding bromine in place of the chlorine when the test strips indicate it’s time.

Draining your hot tub doesn’t have to be a royal pain, nor does it have to take hours.

I’m really excited to get a submersible drain pump with a 25′ hose. No more siding to remove with my drill or garden hoses to hook up.

Just drop this thing in your hot tub (or pool) and watch as it drains it in record time!

Normally my hot tub takes an hour or more to drain. But with this device, I can drain it within 15 minutes! It’s got great reviews, is an Amazon’s Choice product, and comes with free Prime shipping.

Do be aware, it has to be all the way submerged before it will turn on. And then, course, when the water gets down to the very bottom, it will turn off, leaving a small amount of water in your tub.

But that can easily be handled with a  wet-dry vac.

CLICK HERE to check current prices on Amazon on the submersible drain pump.

What happens if bromine is too high in a pool or hot tub?

If your chlorine or bromine levels are too high, the good news is you don’t have to drain your pool or hot tub and start over.

The bad news is you should not use the pool or hot tub as long as the levels remain high. Why?

Too much bromine or chlorine in a pool or hot tub can cause any or all of the following:

  • Corroding the pipes and equipment
  • Extra wear and tear on the vinyl cover and headrests
  • Skin and eye irritation and skin rashes

The other good news is that your bromine or chlorine levels in your pool or hot tub will naturally decrease day by day. How long you need to wait before using depends on how high the readings are. But I have found that generally 1-2 days is usally enough.

Want to speed up the process of lowering the sanitizer levels in your hot tub?

Leave the cover off your hot tub for at least 24 hours to allow more water to evaporate. You can also drain a little and top off, or if the water levels are a little low anyway, just top off from the hose.

Then just test again with a test strip and adjust everything as needed.

What happens if you mix bromine and chlorine?

As I mentioned above, it’s totally OK to transition from one type of sanitize to the other.

There’s also not anything wrong with using both bromine and chlorine together. In fact, a lot of shock products contain chlorine and get used even when bromine is used as the sanitizer.

But it’s important to understand the differences and how the 2 chemicals react with one another.

Bromine actually is made up of both chlorine and bromide.

When you combine chlorine with bromine, the bromide ions simply convert the chlorine into bromine. That’s the reason why if you were trying to switch from bromine to chlorine, you’d have to drain the water first.

Otherwise, you keep adding chlorine and it will just convert to bromine.

But obviously, if you do mix the 2 chemicals, just test before using to make sure the levels are not too high.

Eventually, even the best maintenance of your water stops being effective and the water will need to be changed. But many hot tub owners are confused about how often they need to change their water.

I break it all down in a recent article which not only tells you how often to change it, but how to tell from looking and smelling the water too. Just click the link to read it on my site.

Can I use chlorine test strips for bromine?

Yes is the short answer.

In most cases, test strips will measure both chlorine and bromine at the same time. So no matter which one you are using, it will still give you a reading.

Let’s take a look at the test strips I use as an example:

As you can see, the top bar reads both chlorine and bromine and gives you levels in numbers and colors for both.

The color for OK and not OK remains the same whether you’re using bromine or chlorine, making it incredibly simple. In terms of actual ppm (parts per million), go off the following:

  • Chlorine range for pools = 1-3 ppm
  • Chlorine range for hot tubs = 3-5 ppm
  • Bromine range for pools  and hot tubs = 2-6 ppm

So just buy 1 brand of test strips no matter which sanitizer type you’re using, and you’ll be just fine.

Luckily, those test strips are really cheap on Amazon (click to see them on Amazon). Hundreds of near-perfect reviews can’t be wrong, and free prime shipping too!

Final Thoughts

In this article, we took a look at the world of hot tub and pool chemicals.

We explored what the key differences are between chlorine and bromine and why you might want to use one over the other. But we also looked at what were to happen if you mixed the 2 and what to do if the levels get too high.

Do you use chlorine or bromine?

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Jeff Campbell