Converting From Dichlor/bleach To Bromine For Vacation

[jfrisky]

I've been using Dichlor/bleach but am in a quandary about how to maintain sanitation levels during vacations that could be over a week or two. After having dealt with white mold, I can't afford to let sanitation levels fall, even for a short time. For a minute I did some reading about Nature2/MPS for vacation purposes, but it doesn't seem to solve the problem, as it only works with regular applications of MPS - and Chem Geek has stated MPS is gone within about 24 hours. So that's not a vacation solution. My spa instructions specifically state not to use Trichlor to maintain warranty. So it seems a bromine floater would be the solution.

I'm currently maintaining a sanitation level of 3-6+ FC with bleach and shocking with MPS (I still get uncertain but suspicious mold-like symptoms, and heavy MPS shocking seems to clear symptoms - but that's in another post).

Here are my numbers (Taylor k-2006): am maintaining FC 3-6ppm. other #s are

CYA=30, pH~7.5, TA=90, Bor=50, CH=140.

Can't currently get good CC or CD readings due to MPS use - don't have that MPS interference reagent.

I've read Waterbear's Bromine for Beginners. I plan to buy that recommended floater & bromine tabs. My questions are:

1. Will a bromine floater alone keep the spa sanitized during non-use 1-3 week vacations?

2. If I'm ok with converting to bromine gradually, can I skip buying the Sodium Bromide? and generally how long will it take for the bromine to take over the sanitation role?

3. What type of chlorine is "included" in Bromine tablets? Are there more than one type of bromine tabs and what should I be looking for? Can I avoid trichlor?

4. Can you briefly explain the interaction between Chlorine and Bromine? Clorine seems to be necessary as well, after each use, and you mention chlorine activating bromide reserve... so are we maintaining both chlorine and bromine levels, or will this be a single FC reading? This part is a bit confusing - and I want to understand what I'm actually doing.

5. I'd prefer continuing to shock with MPS pretty heavily. It seems to work better at oxidizing whatever weird 'surface water' symptoms still plague my spa. Will this be ok and how does MPS interact with bromine? OR - Will it work to switch it around and add MPS after each use and shock weekly with bleach?

6. Should I change any of my numbers above for a bromine spa?

7. Lastly, what will I need to add to my K-2006 kit?

[chem geek]

1) A bromine floater would likely last 1 week, but not 2 and certainly not 3. For that kind of length of time you would need something like a saltwater chlorine or bromine generator and even then there would be risks of scaling from rising pH and the sanitation may not be consistently stable, but probably OK.

2) Yes you can skip the sodium bromide and by using bromine tabs you'll get a mix of chlorine and bromine for a while until the bromide builds up from spent bromine.

3) The chlorine in BCDMH bromine tabs is identical to any other chlorine source once dissolved in the water. The other type of bromine tabs are DBDMH that contain only bromine. Some people like the DBDMH better.

4) Once there is a sufficient amount of bromide, any oxidizer added to the water (chlorine, MPS, ozone) will oxidize the bromide to make bromine. At that point, you have a bromine spa and any chlorine that is used is just temporary, either to shock to help oxidize some bather waste that bromine might have trouble with or to produce more bromine faster than would be released from tabs (say, to handle bather load if you use the spa infrequently -- the tabs are then used to provide a low background level of bromine between soaks).

5) You can use either MPS or chlorine to shock your spa. As noted above, after you build up a bromide bank either one will first oxidize some bather waste if present and then produce more bromine by oxidizing bromide.

6) Your bromine targets should be around 2x the chlorine ones since the units of measurement for bromine are 2.25 times that of chlorine.

7) You shouldn't need to add anything to your K-2006 kit. With bromine, you won't be using some parts of that kit, most notably the R-0003 since you can't measure combined bromine separately -- the Free Chlorine (FC) part of the test will actually measure Total Bromine though you multiply by 2.25 more than with chlorine. So when using a 10 ml sample size, each FAS-DPD drop represents 1.125 ppm bromine while with a 25 ml sample size each FAS-DPD drop represents 0.45 ppm bromine.

[Spanky]

I've had success leaving the tub for 2 weeks by using 2 floaters. Set each one to 1/2 the normal opening and fill them to the max.

Make sure you shock prior to leaving so that the daily demand is as low as possible.

I've never tried 3 weeks but being honest, I'd say that there was enough tabs left for 1 more week

[chem geek]

Thanks for that info. Two floaters at half output rate makes a lot of sense and I'm glad you thought of that and saw that it worked. Turning down the water temp makes a big difference as well where even 80ºF has a slower chlorine loss rate.

[Spanky]

Thanks for that info. Two floaters at half output rate makes a lot of sense and I'm glad you thought of that and saw that it worked. Turning down the water temp makes a big difference as well where even 80ºF has a slower chlorine loss rate.

Yes I did turn the temp down. Not that I was thinking from a chemistry standpoint but more from a economic.

One more point, Chem Geek did raise the issue of pH. I was fortunate in that it didn't become an issue. I think I understand why it worked. Bromine tabs are net acidic but the 24hr circulation pump + my tub's programming turns the main pumps on for 5min every 8 hrs in a "Purge" cycle created enough aeration to prevent the pH from dropping. I believe at that time my TA was about 90 with 50ppm borates (This was before I experimented with lower TA)

[jfrisky]

Thanks for all this info, both of you. Those are really good ideas... the 2 floaters, and aeration for pH. I've learned so much from this forum. Yes, as much as I like the idea of the simplicity of dichlor/bleach, I'm immediately finding it more complicated to continually be mentally calculating how much bleach to add for basic maintenance plus use hours. It does seem it'd be much easier to have the basic levels maintained by a floater and only need to be adding for hours used. Then while on vacation - the 2 floaters is a great idea. Also - if someone is scheduled to come check the place while you're away (or come in to care for pets, which I need) it's easier to ask them to add bromine tabs to a floater weekly than be measuring liquid bleach every day or so. This definitely seems manageable.

I have a very basic, small spa where circulation is triggered by the temp, unfortunately. But I can put it on a timer. When the spa gets kicked on, it'll have a default temp of 100. So I'm thinking... if I let the temp fall to 75-80 before I leave, then use a spa timer to limit circulation to 2 hrs per day - with jets open for aeration, the temp would only go up 4 degrees each cycle, and then fall back down overnight. (it's well insulated and only seems to fall 3-4 degrees overnight if I turn it off) But is 2hrs/day with aeration enough circulation?

[Spanky]

**Follow-Up**

I've just returned from 2 weeks vacation and am happy to report that everything went well with the spa.

My normal running specs:

Ch: 150

TA: 50

pH: 7.6

Br: 3.5

Borates : 50ppm

Temp: 100-101

Preparation:

1) Fill Floater to max with tabs.

2) Reset floater to 1/2 normal opening.

3) Add 2nd floater also set to 1/2 (Based on the dissolve rate of your tabs this may not be necessary but for $15.00 I find it cheap "Piece of Mind" insurance)

4) Raise TA to 90-100 with baking soda.

5) Lower Temp to 80 deg

Results after 2 weeks vacation:

Br: 4.5 ( Yes it did rise )

pH: 7.4 (Slightly lower but still within acceptable range)

TA: 60 (This confirms the net acidity of the bromine and the need to increase TA before starting)

Both floaters had approximately 50% tabs left.

pH did not rise, (most likely due to lack of areation), but TA did drop 30ppm

It would be interesting to hear what what results others have after vacation.

[chem geek]

The bromine tabs are net acidic when accounting for usage/consumption. That's why the TA dropped, but the pH would have dropped as well were it not for carbon dioxide outgassing. Apparently that can still occur to some extent even with the spa covered (though that's surprising). However, I calculate that if one was adding and consuming 2.25 ppm Bromine per day for two weeks (equivalent to 1 ppm FC per day), then the TA would drop by about 10 ppm and the pH from 7.6 to 7.0. That obviously didn't happen so there's something about the chemistry that I don't understand. I assumed that the bromine tabs do something like the following where "DMH" is the core ring for the bromine tab:

BrClDMH + 2H₂O ---> HOBr + HOCl + H₂DMH

HOCl + Br^- ---> HOBr + Cl^-

2HOBr ---> O₂(g) + 2H⁺ + 2Br^-

------------------------------------------------------------------------

BrClDMH + 2H₂O ---> O₂ + 2H⁺ + Br^- + Cl^- + H₂DMH

If instead some of the bromine escapes as gaseous HOBr, then there is less pH drop, but also less TA drop. The only way to have the TA drop a lot and the pH not to drop much is to have carbon dioxide outgassing. Otherwise, acid addition (from any source or mechanism) lowers both pH and TA.

[Spanky]

I believe that the 24hr circulation pump provided some aeration plus my spa is programmed to run a "Purge" cycle every 8hrs. The purge cycle turns the main pumps on for a about 5 mins so this provided the aeration. The air valves were also left in the "Open" position so when the pumps started there was air intake.

My main concern was to avoid low pH. Chem Geek is clearly correct in that the net acidity of the bromine is more of a concern than the floater running out of tabs. That's why I raised the TA and left the air valves open.

I added 3 oz of baking soda before I left, and checking the pool calculator, my starting TA may have been closer to 80 not 90 (sorry my miscalculation)

[waterbear]

a few points. Once you use bromine tabs you would need to drain and refill to go back to dichlor/bleach.

Also, bromine chemistry is different than choirne chemistry. You can shock with bleach or other form or chlorine or you can shock with MPS and have exactly the same results, you increase the amount of hypobromous acid in the water. You can also use ozone to create the hypobromous acid.. It does not matter. Therefore MPS is not going to act the same in a bromine system as it does in a chlorine system or a silver/MPS system. In other words, forget everything you did with dichlor/bleach if you switch to bromine. It is a different animal and needs to be treated as such.

[PreservedSwine]

a few points. Once you use bromine tabs you would need to drain and refill to go back to dichlor/bleach.

Also, bromine chemistry is different than choirne chemistry. You can shock with bleach or other form or chlorine or you can shock with MPS and have exactly the same results, you increase the amount of hypobromous acid in the water. You can also use ozone to create the hypobromous acid.. It does not matter. Therefore MPS is not going to act the same in a bromine system as it does in a chlorine system or a silver/MPS system. In other words, forget everything you did with dichlor/bleach if you switch to bromine. It is a different animal and needs to be treated as such.

If you just remove the bromine, and begin using Dichlor- I assumed the dichlor would turn into bromine... until the existing bromine ions were depleted? Or is that hogwash?

[waterbear]

a few points. Once you use bromine tabs you would need to drain and refill to go back to dichlor/bleach.

Also, bromine chemistry is different than choirne chemistry. You can shock with bleach or other form or chlorine or you can shock with MPS and have exactly the same results, you increase the amount of hypobromous acid in the water. You can also use ozone to create the hypobromous acid.. It does not matter. Therefore MPS is not going to act the same in a bromine system as it does in a chlorine system or a silver/MPS system. In other words, forget everything you did with dichlor/bleach if you switch to bromine. It is a different animal and needs to be treated as such.

If you just remove the bromine, and begin using Dichlor- I assumed the dichlor would turn into bromine... until the existing bromine ions were depleted? Or is that hogwash?

Not when tabs are used because of the dimethylhydantion. It works sort of like CYA for chlorine and keeps the bromine from being destroyed (probably by preventing oxidation to bromate but I am not really sure of the exact chemistry). If only sodium bromide and an oxidizer is used (2 step bromine) then eventually (usually within a few weeks) the bromide reserve would be destroyed (by UV and the addition of oxidizer) and the pool would revert back to chloirne.

[PreservedSwine]

a few points. Once you use bromine tabs you would need to drain and refill to go back to dichlor/bleach.

Also, bromine chemistry is different than choirne chemistry. You can shock with bleach or other form or chlorine or you can shock with MPS and have exactly the same results, you increase the amount of hypobromous acid in the water. You can also use ozone to create the hypobromous acid.. It does not matter. Therefore MPS is not going to act the same in a bromine system as it does in a chlorine system or a silver/MPS system. In other words, forget everything you did with dichlor/bleach if you switch to bromine. It is a different animal and needs to be treated as such.

If you just remove the bromine, and begin using Dichlor- I assumed the dichlor would turn into bromine... until the existing bromine ions were depleted? Or is that hogwash?

Not when tabs are used because of the dimethylhydantion. It works sort of like CYA for chlorine and keeps the bromine from being destroyed (probably by preventing oxidation to bromate but I am not really sure of the exact chemistry). If only sodium bromide and an oxidizer is used (2 step bromine) then eventually (usually within a few weeks) the bromide reserve would be destroyed (by UV and the addition of oxidizer) and the pool would revert back to chloirne.

Thanks- I appreciate explantion- I had no idea dimethylhydantion prevented the bromine being destroyed.

[chem geek]

It's not absolute. It just takes longer and I wouldn't say that bromine is destroyed, per se. When you add an oxidizer, bromide gets converted to bromine and when it gets used up it becomes bromide again so this is a cycle. Some oxidizers such as ozone will oxidize some of the bromine to bromate so that is bromine/bromide getting "destroyed" in that it's a one way trip. I do not know for certain if MPS or chlorine do this -- my understanding is that they do not. So the main way that bromine slowly goes away (unless you have an ozonator) is through outgassing. This is where dimethylhydantoin (DMH) may come into play in that it may bind to some of the bromine lowering its effective level so less outgasses -- similar to how CYA binds to chlorine. And DMH may also help reduce the rate of loss of bromine to bromate from ozone. However, I've never seen any equilibrium constants for the DMH/bromine relationship so this is all speculative (though based on some observations some have seen).