Spa Bromine & Spa Shock – Building a Bromine Bank

Dr. Pool posing with Bromine Booster

Bromine is best for spas and hot tubs, for many reasons. it’s more stable in hot water and is affected less by wide swings in pH.

There is one trick you should know about using spa bromine. I’m speaking of Building a Bromine Bank.

The ‘bank’, is actually a reserve of sodium bromide ions in the water. For bromine to be effective, enough bromides need to be available.

Sodium Bromide

3-part-bromine system

Each time you drain your spa or hot tub, your bromide bank goes to zero. To build the level back up again you simply add granular sodium bromide. Brom Booster, as it is known, is 100% granular sodium bromide. Use 2 oz. per 500 gallons to build up the bromide bank in your spa.

You could allow the bromine to come up slowly on it’s own, from the dissolving bromine tablets, but it can take days or weeks before you begin to see a bromine reading in a spa or hot tub.

brom-boosterYou could also crush up 5 or 6 bromine tablets, in a heavy plastic bag, and pour that in the hot tub to raise bromide levels – but, it’s easier and safer to shake in a capful or two of our Bromine Booster.

Spa Shock

The other side of the bromine equation involves activating the bromide ions with spa shock, which converts them to hypobromous acid, the killing form of bromine.

In the normal 3-part bromine system, a spa owner starts with a residual of bromide ions in the water, and then add the bromine tablets to a feeder or floater. There is no home test for measuring bromide ions in your spa, just add the recommended dosage for your spa size.

Hypobromous AcidShocking weekly with spa shock activates the bromide, or converts it into hypobromous acid, or HObr. Once HObr has attacked a contaminant in the water, most are reduced back to a bromide ion again, where the cycle begins anew.

Spa Tablets

bromine-tabsThe beauty of InTheSwim bromine tablets, as detailed in my previous post, is that they contain 27% chlorine! This acts as a built in oxidizer to keep the bromide ions constantly converting a continuous supply of HObr.

So, you don’t really need to shock a spa or hot tub to “activate” our bromine tablets. However, I do recommend that all spas be shocked weekly, more for sanitation purposes, but also to ensure adequate conversion of bromide ions.

spa-shockYou will find that after oxidation of your bromides, using a non-chlorine spa shock, that your bromine level will spike, and that’s because you are really shocking with bromine! The non-chlorine shock is oxidizing contaminants when added, but quickly mates up with free floating sodium bromide ions, to create HObr, which is when the real fun begins!

nabro - purchased from PresenterMediaI’ll leave you with some chemist humor, and the hope that you now know at least something about sodium bromide, or NaBrO.

If you have other questions about spa shock, spa tablets or sodium bromide, give our spa techs a call, or send me an email.


Dr. Pool



Spa Bromine & Spa Shock – Building a Bromine Bank — 6 Comments

  1. I recently changed from chlorine to bromine and refilled my spa. I crushed 2 mini bromine tablets as per pool store instructions and added to water (1085 liters) and added 1/2 cup of non-chlorine Aqua Brite Plus. That was yesterday morning. Half of the crushes bromine is still sitting on the bottom of the spa and won’t disssolve. How long does this take? After it dissolves the plan is to add a floater at setting 3 and then add 1/4 cup Brite Plus every 2 weeks.

    I switched from chlorine because no matter what I did the cya acid always became too high and I’ve had to drain my spa 3 times in the past 3 months. I’m hoping the bromine is less of an annoyance as I’m going into winter and won’t be able to drain and refill again until Spring.

    Any help is appreciated.

    • Hi Steve, the crushed bromine tablets are used to raise the “Bromide Bank” or residual of bromide ions in the water, so that a reading will register. The Aqua brite plus is used to re-activate the bromides, turning them into bromine. Daily use of bromine tablets is also used, to maintain the levels. Instead of crushing up tablets, which can be unpleasant and less effective, use Bromide Booster, or similar granular bromide treatment, whenever you drain the spa and refill. Bromine is best for spas, keep at it, you’ll get there – good question, thanks.

  2. I have a new spa,and I can’t get a bromine reading. I went to my local spa supply place and brought new bromine, same result “0”. Should I shock the tub to get this going. Every product company say’s that I shouldn’t have to do that. Any suggestions on getting a reading? I have new chems and new test strips. Help

    • Hi there – Great Question. You probably have no bromide ions in the water. to use bromine tablets, you first add bromide ions, like Brom Booster, just an ounce or two, and then you can begin to see a bromine reading from using bromine tablets. Bromide ions can be reactivated with shock. After a fresh refill on a hot tub, you have to rebuild the ‘bromine bank’, by adding bromide ions directly. Most people will shock the pool soon after adding. Then you will get a reading on your test kit.

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