Spa Bromine and Spa Shock: Building a Bromine Bank

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!

34 thoughts on “Spa Bromine and Spa Shock: Building a Bromine Bank

  1. Mona Grier

    Bromine Bank. I am a first time hot tub owner and a senior. I had a spa company do my start up about two weeks ago because I was clueless. When I started learning about the bromine bank I contacted them to ask if they established one. They did not and were not helpful. My bromine level barely registers when tested. I have a floater and use non chlorine shock. Do I have to drain hot tub and start over or can I establish a bromine bank now. All other test readings are within range. The water is clear. It has only been used four times since startup. Thank you.

    • Hi – to increase the bromine bank (the level of bromide ions) in the water, all you need to do is add 1-2 tablespoons of Bromides, such as what we have in our Brom Booster product.

  2. We have a new 300-gallon hot tub, and the manufacturer says we CANNOT use bromine tablets. I’ve been using the granular bromine, along with the oxidizing spa shock, and after treatment, the chemistry is fine for about 24 hours, then all of a sudden, the bromine goes down to 0. And now our hot tub has a funky smell that I can’t seem to get rid of. Any suggestions for what to do?

    • Hi Joanna, how about 1″ chlorine tablets? It is important to maintain a chlorine residual at all times, otherwise the smell, mold/mildew/bacteria… that’s what tablets are good for – an even, steady level. Also, using a mineral stick can reduce the amount of chlorine/bromine needed to keep the water fresh, so that’s another route.

  3. I have a new 500 gallon hot tub and want to go with bromine and non-chlorinated shock. I’ve got 99% sodium bromide granules which I will add after balancing the alkalinity and pH. I’ve also got, when ready, a floater with a couple bromine tablets set per the hot tub manufacturers instructions.

    The big question is; do I need to shock immediately after adding sodium bromide to get bromine levels in the hot tub safe for use?

    I understand that the tablets have an oxidizer built-in. But does that mean that they work with both the bromine in the tablets and my bromide ions from my reserve, or is the oxidizer in the tablet strictly designed for activating bromide ions?

    Thank you for the time you take to answer these!

    • Hi Loren, Allow the bromides a few hours or overnight to dissolve fully, then give it a shock the following day, then check the bromine level after a few hours. Once it drops down a bit lower, if very high, add the bromine floater. The BCDMH type of bromine tablets do contain chlorine as well, about 26%, partly as an oxidizer, but also as a sanitizer. You will still want to use your non-chlorine shock regularly.

      • Thank you so much for the details, that’s I’ve been needing to fill in the gaps!

        One more thing is I’m wondering what ppm of bromine am I looking to achieve after shocking? And sometimes I see recommendations to shock after each use (I want to use it every other day), so if I choose to shock after each, would I be looking to achieve my same ppm of bromine as I would during a routine weekly shock?

        • Hi Loren, that’s a good question, and the answer is roughly 4x the normal level. Most residential bromine spas are run in the 1.5-3.0 ppm range on a daily basis. A shock treatment would/could/should raise the bromine level to the 8-12 ppm range. Then you should leave the cover at least half-open for an hour, to allow it to gas off. This wastes a lot of heat. And, it will also result in a much higher daily bromine level, if you are shocking every other day. In a tub, you shock both to remove contaminants and waste, and to kill any bacteria that has escaped the normal bromine levels, and also, shocking a spa treated with bromides, creates (or re-creates) bromine. If it was just you using the tub, shocking every other day would be too much, unless you test the water after use, and see that bromine levels have fallen to near zero. In such a low use spa, I think I would lean towards weekly shock. Your experience over time will guide you in the correct tempo for shocking the spa, both to elevate bromine levels, and to ensure clean and clear water. Shocking is also useful for removing bromine odors and for treating cloudy water. (but remember to drain every 3-4 months)

          • I think I’m understanding this now much better. There are all these nuances that are left out of the info I’ve found online or even from my owners manual. It makes the difference between just robotically adding chemicals vs being able to tackle any issues that come up that aren’t standard. I can’t thank you enough!

  4. Stephanie

    Hi starting up a new cedar soaking tub (550 gallons). I balanced the water and added 3.5 Oz bromide (bit by bit) and 2 capfuls of oxyspa. My bromine levels continue to read 0 (using the SpaFrog test strips). Not sure if it needs more bromide, to be shocked again… I haven’t added the SpaFrog float yet. Also- no jets (but we have agitated the water with the paddle). Will the tannins coming off the wood impact any of the readings? Thoughts? Thank you!

    • Hi Stephanie, I don’t think that the tannins would impact the readings, although it may use some of the bromine. I would try shocking again, heavier this time, 3-4 capfuls. If the test still reads zero, can you smell any bromine? If so, perhaps the strips are bad. Sometimes it can take a few days for the bromine bank to build up.

  5. Katherine

    Hello,
    So I just got my hot tub up and running. I did all my start up chemicals and everything tested fine except for calcium hardness.

    A few days later I got calcium harness increaser, and now when I tested my water, everything else is fine except the bromine.

    The bromine levels are 0, my hot tub is a 2014(?) utopia Niagara caldera spa. It has a special place to put the frog system bromine cartridges, and so we thought maybe if we put it in a floater it would help the levels.

    Still reading 0 which the test indicates is not ideal. Is it normal for the bromine levels to drop to 0ppm In under 3 days like that? And is it necessary to shock it every time it’s low or is there another issue at hand possibly? Thanks in advance,

    • Hi Katherine, each time you drain the spa, you will need to add Bromine Booster, which are granular bromide ions, which make up what we call the ‘Bromine Bank’, and then when you shock the spa, the bromides are converted into bromine. It takes weeks to get a bromine reading otherwise, if you don’t add an ounce or two of Bromine Booster. Another trick is to pulverize 2-3 bromine tablets, dissolve them in water and add to the spa, but that still may not put enough bromide ions into the water. There is no test for bromides, so the bromide ion booster is the best bet, per label dose.

  6. Hello,

    Our hot tub is 3 weeks old. I believe I managed to build my bromine bank because the bromine level of our hot tub goes over the ideal bromine level after i shock the hot tub, and I read that I just have to wait it out or air it out to get the level down, which actually works. I always have a bromine tablet dispenser floating in the hot tub when it is not in use, but about two days after shocking the hot tub, the bromine level goes below the ideal level and stays that way until I shock the hot tub again the following week. I shock the hot tub once a week, so most of the time, it goes up to 4-5 days when the bromine level is below the ideal level. Does it mean my bromine tablets are not working? Can you please advise how I can keep the bromine levels on its ideal level without having to shock the hot tub more than once a week? Can I use a little dosage of Bromine Start even though the label says I should use it after water refill? I get a little confuse over which product I can use to get the bromine level up without having to shock the pool.

    • Hi, you could try using more bromine tablets, if you have not yet, filling the floater, or adding a second one. You could add a small dose of the bromides (Bromine Start), just a teaspoon or so, that will help it last longer after shocking, but also will raise the level much higher with shocking, so don’t over-dose it.

  7. Hi,

    I have a 2017 Swim Manufacturer Swim Spa.

    I use two floating dispensing units that I leave in the spa 24/7 with bromine tablets.

    I as put in 6oz of Spa Complete once a week

    I then put in 2oz of Spa Scale and Stain once a week

    and I put in 4oz of Spa Shock once a week or after every time I swim.

    By adding the Spa Shock every day is that why my Bromine
    level is always high?

    If so if I’m swimming 6 days a week how often do I add the Spa Shock?

    Thank you!
    Ruth

    • Hi Ruth, I would add the shock only once per week, or even once every two weeks. As long as you have a bromine reading of 3 ppm or higher, the spa shock is not needed in most cases.

  8. Darryl Kropp

    Very helpful article! I recently switched to Br from Cl and this explains a lot of what I have been struggling with.

  9. I’ve had my spa 14 years and still don’t really understand the chemistry. I have learned less is better… . anyway, I never created a bromine bank until a couple years ago. But now I’m trying to understand it. I always got reading after filling my tub, putting brom tabs in and balancing PH and alki and then shocking. At first after banking with sodium bromide I thought I didn’t need to use brom tabs anymore. Just shock more often to keep things in balance. But now I realize you still need to use the tabs. So I’m really questioning the need for sodium bromide banking at all. My strips show free chlorine. I assume it is showing me free bromide as I do not add any chlorine and I get a reading. Is this showing me my bromine ion level? How can I determine when to put brom tabs in? I’m afraid the brom tabs are just saturating my spa over a period of a couple months. Why do I need to keep adding the brom tabs? help me understand

    • Hi Tim, If you are able to easily test for bromine (or chlorine, same test*), then you may not need to add bromides. For many people, it is hard to get a bromine reading after a fresh fill of new water, unless large amounts of tablets are used, so many people add a few tbls of bromide ions to the water, and use fewer tablets. You are correct that you could use bromides and then just shock the spa once or twice per week, but tablets are better for a more consistent and constant bromine level, dissolving slowly to keep bromine steady and avoiding peaks and valleys or periods of very high bromine, for the first 24-48 hours after adding shock chlorine to boost bromine levels. *for the test kit, pool and spa kits and strips that test for chlorine are also testing for bromine (in the same test), bromine is 2.5x heavier than chlorine, so whatever chlorine reading is displayed, you multiply by 2.5, to determine the equivalent bromine reading. For example, if your test kit shows 1.0 ppm of chlorine, and you are using bromine in the spa (or pool), the bromine level is 2.5 ppm. So, my method after draining spa is to add an oz. or so of bromides and then a scoop of shock (chlorine or non-chlorine), to oxidize the water. Then I put 4-5 bromine tabs into the floater, replaced every week. The tabs help keep a constant bromine level during the week. After adding the tabs I also add a scoop of spa shock, to oxidize (shock) the water, unless I have been out of town, or the spa has not been used during the week, and the water looks great, etc.

  10. Camila Henriques

    Is it safe to use the spa while there are still bits of crushed up bromine tablets swirling around?

    • Hi Camila, probably yes it would be safe, unless you have sensitive skin, I would limit the soaks to 10 mins or so and keep your head above water, maybe shower afterwards. Are you using crushed tabs to elevate bromide ion levels? You can use our Bromine Booster, which dissolves instantly, and is concentrated bromides, so you only need an ounce or two.

  11. Hi, we put in a 24,000 gallon in ground bromine pool this year. We have struggled to get any bromine reading. 24 hours after we shock, it goes back to zero. How much bromine booster would we need to add to our pool? Thank you!

    • Hi Lisa, that would be about 100 oz of bromide booster, or about 3 bottles, based on a dosage of 2 oz per 500 gallons. But no telling what the level is now, so I would start with maybe 1 bottle (32 oz) and adding more if needed.

  12. john fisher

    Refilled spa water and added way too much sodium bromide to start the bank (oops). However, shock treatments (non-chlorine) even as they approach the recommended ratio, don’t result in stable Bromine readings (Lamotte ColorQ). After 3rd shock I got Br. Of 5.5 but a few hrs. later it was .4. Next shock got me up to 10.0 but overnight it went down to 1.1. ???? Ph and Alk are good. No one has uses the spa since refill.

    • Well John, that’s a strange one. Either the bromides being high are causing a problem, or something else is consuming the bromine, some contamination. So, either replace some of the water to lower the bromides and refill again, and see how that does, or just super-duper shock it, up to 25 ppm or so, and then see if that will ‘break’ whatever is consuming the bromine.

  13. I am trying to build up my bromine bank. I’ve added the powdered bromine, added the shock, and am using the tablets. Still 0 on the strips. The only time I got it above 0 was when I added a cup of bleach and even then it only stayed good for a day and then fell back to 0. What am I doing wrong?

    • Hi Lindsey, how’s the pH and alkalinity level? High pH could affect a reading. Is the spa covered? Uncovered spas will lose levels fast. Is the spa ‘high use’? Lots of people, everyday? Creates a high bromine demand. Otherwise, I might suspect that the test strips are expired or faulty? Or there could be a high level of organics in the water, invisible, but ‘consuming’ bromine faster than you can add it. Might try to drain half and refill (adding more bromides). Also could be low bromide ion levels (the powdered bromine, or Brom Booster, if the ‘bank’ is not large enough right now – although no way to measure those easily, so you rely on the package label and your own experience.

  14. 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.

    • Davy Merino

      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.

  15. 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

    • Davy Merino

      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.

  16. […] in your spa water. For a bromine spa, using an oxidizer weekly helps to maintain a consistent bromine bank in your spa water. Activating bromine ions with spa shock converts them to hypobromous acid, the […]

  17. […] weekly is important to activate bromide ions, and keep the spa healthy. See Dr. Pool’s recent post on Building a Bromine […]

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