General bromine questions.

[Danmickread]

Hi,
I am refilling my spa soon and want to do it right with the 3 step bromine system and I have a few questions.

On previous refills I just added the bromine tabs and used a granular bromine product which can be used as regular sanitizer or as a shock treatment (I think it's a mixture of sodium bromide and dichlor) but found I had to keep adding this regularly at the beginning to keep the level up.
How would this process be working, would adding the granular product be giving me sanitiser and at the same time building up a reserve (once it's been used up and converted back to sodium bromide) and then the tablets Would do there job once the reserve is built up? Or am I way off with this theory?

Do the bromine tablets themselves add bromine into the water or do they just turn the sodium bromide into bromine that's why u need a bromide reserve?

If u follow the 3 step process and create a 30ppm sodium bromide reserve at the start does this mean u could have a bromine sanitizer level of anything up to 30ppm if added enough chlorine or non chlorine shock? And as time goes by does the reserve level increase from ur tablets?

Is shocking ur spa really just raising the bromine level higher than normal which can be done by turning sodium bromide into bromine either by adding chlorine or non chlorine shock?
If so and there is no bromide reserve then adding chlorine would just put chlorine sanitiser into the spa? And adding non chlorine shock would do what?

If I am correct in my thinking then what sort of level of bromine should u have to shock and how much chlorine or non chlorine shock would u need to add to raise it to this level (assuming u have a bromide reserve)?

One last thing.
Is is possible to super shock existing bromine water (I want to super shock my tub before I drain and refill). I have read u need to raise the level to 50ppm chlorine, what level would u need for bromine and how would this best be done.

Thanks in advance

Dan.

 

[chem geek]

Dan,

Welcome to TFP!

There are two types of bromine tabs. The most common, BCDMH, adds both bromine and chlorine into the water. The other, DBDMH, adds only bromine. If you started out using BCDMH without initially creating a bromide bank by adding sodium bromide, then the chlorine from the BCDMH wouldn't have any bromide to create bromine and you'd really have a mixed bromine/chlorine spa. After some days or perhaps a week or so, the bromine would get used up and produce enough bromide so that subsequently the chlorine from tabs would convert that back into bromine. So the normal thing to do with the 3-step bromine system is to start out by adding sodium bromide so that the chlorine in your tablets can make more bromine. You also need this bromide bank initially so that you can add more oxidizer (usually chlorine, but can use MPS as well) after bather load.

You are correct that if you created a 30 ppm bromide bank, then if you added chlorine or another oxidizer you could get up to a 30 ppm [EDIT] (actually, 60 ppm, if bromide is measured as Br^- while bromine is measured as Br₂) [END-EDIT] bromine level with any excess chlorine creating an additional chlorine level.

Yes, shocking is as you described though is not normally needed to do regularly on a time schedule, but is rather based on bather load. Instead, you tune your bromine tab floater output to cover your usual background usage and then just add chlorine manually for the varying part of usage. So if you use the spa consistently the same every day or two, you might be able to dial up the bromine tabs to provide all the bromine you need, but with high bather loads you might still need to add more oxidizer after a soak. If you don't use the spa frequently, then the bromine tab floater level would be set lower to keep the bromine level up in between soaks while you would add chlorine after your soak to oxidize your bather waste (it mostly converts bromide to bromine, but will also oxidize some fast-to-oxidize waste directly).

If you have no bromide bank, then adding chlorine just has chlorine in the spa and adding non-chlorine shock (MPS) just has MPS in the spa -- that is, you don't have a bromine spa at that point.

As for superchlorinating, we don't have experience with that for bromine spas. With Dichlor or bleach superchlorinating a chlorine spa, the actual active chlorine level is somewhat limited due to the high CYA in Dichlor or due to the high pH in bleach. With a bromine spa with a large bromide bank, you will get a high bromine level that is not moderated much in its strength unless bromine tabs were used a lot (they leave DMH which may have some moderating properties similar to CYA, though perhaps not as strong in moderation). It'll probably be OK, but I don't know for sure. You could use a product such as Spa System Flush that should work in either a chlorine or a bromine spa.

Richard

 

[Danmickread]

Dan,

Welcome to TFP!

There are two types of bromine tabs. The most common, BCDMH, adds both bromine and chlorine into the water. The other, DBDMH, adds only bromine. If you started out using BCDMH without initially creating a bromide bank by adding sodium bromide, then the chlorine from the BCDMH wouldn't have any bromide to create bromine and you'd really have a mixed bromine/chlorine spa. After some days or perhaps a week or so, the bromine would get used up and produce enough bromide so that subsequently the chlorine from tabs would convert that back into bromine. So the normal thing to do with the 3-step bromine system is to start out by adding sodium bromide so that the chlorine in your tablets can make more bromine. You also need this bromide bank initially so that you can add more oxidizer (usually chlorine, but can use MPS as well) after bather load.

What does bdcmh stand for so i know what im looking for? And what about the process i explained i was doing before with the granular product am i thinking along the right lines?

You are correct that if you created a 30 ppm bromide bank, then if you added chlorine or another oxidizer you could get up to a 30 ppm bromine level with any excess chlorine creating an additional chlorine level.

Yes, shocking is as you described though is not normally needed to do regularly on a time schedule, but is rather based on bather load. Instead, you tune your bromine tab floater output to cover your usual background usage and then just add chlorine manually for the varying part of usage. So if you use the spa consistently the same every day or two, you might be able to dial up the bromine tabs to provide all the bromine you need, but with high bather loads you might still need to add more oxidizer after a soak. If you don't use the spa frequently, then the bromine tab floater level would be set lower to keep the bromine level up in between soaks while you would add chlorine after your soak to oxidize your bather waste (it mostly converts bromide to bromine, but will also oxidize some fast-to-oxidize waste directly).

so are u saying i just need to make sure the bromine stays at a normal level even after a soak by adding an oxidiser? I thought ur supposed to shock on a weekly basis to a higher level to say 15ppm to boost the sanitising process if u like. If so what is this level and how much oxidiser so i add to obtain this. Or how much chlorine or is needed to raise the bromine level by 1ppm.

If you have no bromide bank, then adding chlorine just has chlorine in the spa and adding non-chlorine shock (MPS) just has MPS in the spa -- that is, you don't have a bromine spa at that point.

So will the mps be doing anything on its own?

With the super shocking i guess its best to drain and just shock with fresh water and chlorine then?

thanks for all ur help. i would be so stuck without this forum.

As for superchlorinating, we don't have experience with that for bromine spas. With Dichlor or bleach superchlorinating a chlorine spa, the actual active chlorine level is somewhat limited due to the high CYA in Dichlor or due to the high pH in bleach. With a bromine spa with a large bromide bank, you will get a high bromine level that is not moderated much in its strength unless bromine tabs were used a lot (they leave DMH which may have some moderating properties similar to CYA, though perhaps not as strong in moderation). It'll probably be OK, but I don't know for sure. You could use a product such as Spa System Flush that should work in either a chlorine or a bromine spa.

Richard

 

[chem geek]

BCDMH stands for bromochlorodimethylhydantoin or 1-bromo-3-chloro-5,5-dimethylhydantoin while DBDMH stands for dibromodimethylhydantoin or 1,3-dibromo-5,5-dimethylhydantoin.

As for startup, add sodium bromide initially, at least 30 ppm though 50 ppm would be OK. If you find you aren't getting high enough bromine levels, then you either don't have the bromine tab floater turned up enough or you aren't adding enough oxidizer (chlorine or MPS) after your soak. Simply adding the sodium bromide does not build up sanitizer -- it builds up "potential" sanitizer, but you need to oxidize it to turn it into bromine, hence adding chlorine or MPS after a soak if needed.

Shocking on a weekly basis is not always necessary though it does say to do so in Using Bromine in a Spa, but for reasons other than keeping up with bather load. When you soak, the ammonia, urea, creatinine and other organics in your sweat and urine need to get oxidized so you need more after a soak. If you soak regularly, then turning up the bromine tab feeder may be able to provide enough bromine to handle it (if your bather load is regular, but not too high). If the bather load is higher or irregular (i.e. not every day or two), then you will need to add oxidizer after your soak in order to oxidize the bather waste. Adding chlorine or MPS after the soak oxidizes some of the bather waste and oxidizes bromide to bromine to handle the rest and to provide sanitation. You want to add enough oxidizer so that you have a measurable (2-4 ppm or more) bromine level at the start of your next soak.

As for how much oxidizer is needed, this depends on whether or not you have an ozonator. An ozonator will also oxidize not only bather waste, but will oxidize bromide to bromine. The amount of oxidizer needed for bather load is roughly 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) for every bather-hour of soaking -- note that this is independent of spa size. Because of your bromine tab floater, the amount you need will be less. If you have an ozonator, it should be far less, perhaps half or less. You just have to test and see how much you need to add to ensure the measurable bromine level at the start of your next soak. You'll figure out your "how much per bather-hour" pattern pretty quickly. I think that the weekly shocking is probably only needed if you are relying mostly on your bromine tabs for the bromine level and aren't adding chlorine after your soak nor have an ozonator. If you are adding chlorine after your soak (especially if you initially use Dichlor and then after cumulatively adding around 33 ppm FC over weeks then switch to 6% unscented bleach) that the shocking probably isn't necessary. Basically, chlorine is a better oxidizer so if you are using it after soaks then you are keeping up. If you are using only bromine, then you may need to shock as much as weekly to oxidize things that bromine doesn't. You can just see how things go and shock with chlorine "as needed" if you notice the water quality not being ideal (clear with no smell except "clean" faint bromine smell).

1 ppm of chlorine will raise the bromine level by 2.25 ppm though for simplicity most test kits show 2 ppm bromine as being equivalent to 1 ppm chlorine.

If there is an excess of MPS because you don't have enough bromide in your bromide bank, the MPS will oxidize some bather waste. Chlorine, bromine, MPS and ozone are all selective oxidizers and oxidize different chemicals at different rates, but they all tend to get rid of bather waste. Generally, ozone and chlorine do the best job while bromine and MPS less so. This is why those that use only MPS as in the Nature² low-chlorine system usually need to shock with chlorine once a week or so. If you use chlorine as your oxidizer, you shouldn't need to shock and it's a lot less expensive as well.

As for the superchlorinating, I don't know if you need to drain/refill/superchlorinate and then drain/refill or neutralize the chlorine (drain/refill removes whatever gets chlorinated and incompletely oxidized). That is a lot of extra work, but again I don't know what the bromine spa people normally do for decontamination. You won't be exposing the spa to the high bromine levels (given the bromide bank the chlorine will oxidize bromide to bromine) for very long.

 

[Danmickread]

Can i use chlorine granules instead of chlorine to shock cause i have a tub of this already?

Thanks for all ur help

Dan

 

[chem geek]

Yes, you can use chlorine granules, which I presume to be Dichlor, for shocking to create more bromine from your bromide bank. Though more expensive than bleach, if you already have it then it's a sunk cost so you might as well make good use of it.