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Spa Bromine and Spa Shock: Building a Bromine Bank

Bromine is best for spas and hot tubs for many reasons. It's more stable in hot water and is affected less by pH fluctuations. 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

Spa bromine booster

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 is 100 percent granular sodium bromide. Use 2 ounces per 500 gallons to build up the bromide bank in your spa.

You could allow the bromine to come up slowly on its 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.

You 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 Brom Booster.

Spa Shock

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 three-part bromine system, a spa owner starts with a residual of bromide ions in the water and then adds 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.

Shocking 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

Spa bromine tablets

The beauty of In The Swim bromine tablets, as detailed in this post, is that they contain 27 percent 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.

You will find that after oxidation of your bromides using a non-chlorine spa shock, 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!


In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.