- Categories: Spa Cleaning
Bromine: guide to the no.1 spa sanitising chemical
The steaming heat of your hot tub is a harsh environment for sanitisers to work properly. So you need something tough; something with resilience that will nuke that unwanted algae and bacteria lurking in your spa pool. What you need is spa bromine.
However, there’s a lot of misconception about spa bromine and how it can safely, and effectively, sanitise your hot tub. So let us take you on an informative bromine ride.
In this bromine guide, we’ll cover:
Let’s dive in.
What actually is bromine?
Bromine stands out as a unique entity in the realm of science due to its peculiar characteristics. As a red, vapor-emitting liquid at ambient temperature, bromine exhibits an unconventional nature. What sets it apart even further is the fact that it represents the only non-metallic element existing in liquid form.
This red liquid has quite a sharp, unpleasant stench, so bromine was named after bromos: Latin for “quite the stench” – or something like that.
Bromine exists in nature as a compound (mostly as bromide salts). Bromide salts are extracted from places where they occur naturally, such as the Dead Sea.
The extracted bromide-rich solution is then mixed with air and chlorine gas, which displaces the bromide via oxidation. This reaction forms sodium chloride, which releases oxidised bromide as a red gas. Then, it gets collected, condensed, and purified. This collected gas is the chemically reactive bromine.
And if you’re even more interested in delving deeper into the science, you can read more about it here. However, chemically reactive bromine isn’t what you’re putting into your spa pool. So how are your spa pool bromine tablets different?
How is spa pool bromine made?
Spa pool bromine tablets are actually bromo-chloro-dimethylhydantoin or BCDMH. This is a compound that contains active bromine bonded with chlorine and nitrogen.
This explains why those that have an allergy to chlorine cannot bathe in bromine sanitised water. When you put spa bromine tablets (BCDMH) into water, hypobromous acid (HOBr) begins to form from the bromine.
Hypochlorous acid (HOCI) will form from the chlorine, as long as the pH is between 6.5-9. That shouldn’t be a problem considering the pH of your spa should be between 7.2-7.4.
HOBr has the antimicrobial properties your spa water needs to kill bacteria and other pathogens while HOCI has the oxidising properties. After HOBr has destroyed bacteria it turns into a bromide ion (a less reactive form of bromine holding onto an extra electron). Then, HOCI comes to the rescue and oxidises the bromide ion back into HOBr.
So good old chlorine actually helps bromine to do its job!
Who should use bromine to sanitise a spa?
Bromine is really versatile and can be used by most spa pool owners.
Do you find yourself in one of the following circumstances?
- You’re sanitising your spa for the first time.
- You’re sanitising your spa for the millionth time, but you need a refresher.
- Got an ozone unit and need to sanitise your spa.
- Decided to switch from chlorine to bromine to sanitise your spa pool.
If one of these sounds like you, then stick with us. We’ll cover the essentials first, and then give you the lowdown comparison between chlorine and spa bromine, before finishing up with some fascinating science around bromine as an element.
How to use spa pool bromine tablets to sanitise your spa pool
We’ll get right down to the nitty-gritty, in case you’ve got friends coming around, and you want to impress them with a sparkling spa pool.
Step 1: Get your equipment and supplies ready
You’re going to need the following:
- Safety gloves, goggles, and a mask.
- A tablet feeder.
- Spa pool bromine tablets.
- A bromine testing kit.
- Either di-chlor, lithium chlorine or non-chlorinated shock.
Step 2: Check your water chemistry
You need to balance your spa chemistry before you sanitise with bromine. Make sure these are at the right levels:
- pH: it must be between 7.2-7.4 for bromine tablets to do their job.
- Alkalinity.
- Calcium hardness.
On this article you can learn more about spa chemicals and how to balance your spa chemistry. You can also check out this helpful video about hot tub chemistry.
You may need to shock your spa pool before you add bromine. Shocking it will actually help the bromine to work more effectively.
Step 3: Make sure everything is running properly
Once you’ve got the chemistry sorted, you’ll need to check that your pool is at the right temperature, and the filtration system is running.
All checked and ready? Great – now we get to the good stuff!
Step 4: Add spa bromine tablets to your spa pool
It’s always best to read the manufacturer’s instructions, which you should do next. We’re dealing with tablets here, not liquids or granules. So, as a general rule of thumb, start with one spa bromine tablet for every 600 litres of spa water.
Remember how we mentioned that you may be looking to use spa bromine under different circumstances? Here’s where you can skip to the section that best applies to you.
Starting from scratch: spa pool start-up with bromine
You’re the owner of a brand-new spa pool? Congratulations! When you first fill your spa with fresh water you’ll need to:
- Aim for a bromine reading of 3-5ppm (parts per million).
- Maintain this for one hour.
- Then add additional bromine tablets as needed.
Fill your tablet feeder to capacity or turn your inline feeder up to max on the control valve to reach this reading.
How to add bromine tablets to a floating tablet feeder
- Carefully add bromine tablets to your tablet feeder and secure the feeder lid.
- Place the feeder into your spa and hold it under the water for a few seconds.
- Let the feeder bob around in your spa whenever it’s not in use.
If you have an ozone unit, a floating tablet feeder is the easiest way to keep spa bromine levels topped up.
You’ll just need one or two tablets dissolving in your feeder rather than a few.
How to add bromine tablets to an inline tab feeder
- Turn your filtration system off.
- Turn the feeder control valve off and wait one minute to allow any gas to disperse.
- Twist the feeder cap open – keep your face away and do not inhale the fumes.
- Carefully place bromine tablets into the feeder and screw the feeder cap back on.
- Reset the feeder control valve to your regular setting or start at 50%.
- Test the bromine levels every half an hour or so until it’s reduced to 3-5ppm.
Now your spa is ready. You can hop in for a much-deserved soak!
Switching from chlorine to bromine sanitiser
If your spa has an ozone unit, you still need to top up sanitiser levels with bromine tablets; you’ll just be using a lot less. It’s easier if your spa is currently sanitised with chlorine as all you’ll need to do is stop using chlorine and start using bromine.
Unless chlorine is distributed by a tablet feeder or salt chlorinator. When residues of chlorine and bromine come into contact with each other, the results can be dangerous.
If you’re in this situation, you’ll need to:
- Replace your tablet feeder.
- Discontinue using a salt chlorinator.
- Then, drain your spa and flush the lines.
It’s worth noting that once you start using bromine, it can be difficult to go back.
What about switching back to chlorine, after using bromine?
If, down the track, you decide to switch from spa bromine to chlorine sanitiser, the process can be tricky.
Adding chlorine to a bromine sanitised spa will only make the bromine stronger, so you’ll need to drain and refill your spa instead.
Maintaining the sanitising effect of bromine
Depending on how frequently your spa pool is used, test for total bromine levels every one to three days.
Then you’ll only need to top up spa bromine tablets during times when a total bromine reading is lower than 3ppm or when a bromine tablet has dissolved completely.
Because it’s now just a case of maintaining regular spa bromine readings at 3-5ppm. As easy as all of this may seem, bromine isn’t foolproof all of the time.
If your bromine readings are lower than 3ppm or higher than 5ppm, we’ll guide you through what to do next.
Where can I find bromine tablets?
Spa pool bromine tablets can be found at speciality spa supply stores. You might also want to check the bromine dispenser.
But it doesn’t end there. You’ll need a few more supplies than that to keep your tub happy. Check out our spa sanitiser guide with everything you need to know to keep your tube shiny and healthy.
Happy soaking!
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Hey! I'm Adrian, founder and pool expert here at Dolphin Pacific. I love spending time with family, fishing, and have been known to brew my own beer.
