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Intro And Question About Bromine Spas


dlleno

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Hi. new member here, but I've been lurking/reading for a long time. I'm an old-school bromine portable spa guy since the early 1990s.

First I'd like to thank the authors of the stickies here, and for the opportunity to join the discussions and for the chance to learn: There's some great info (and members) here. In particular, I'd like to call out a couple of important learnings for myself, and ask some related questions:

1. Use sodium hypochlorite as the oxidizer of sodium bromide. who'da thought! I'm historically (or hysterically perhaps) entrained in the world where di-chlor is the only permissible form of chlorine that a portable spa will tolerate. Thats essential advise for spa stores, to be sure, but its good to know that one can use cheaper alternatives at least when the objective is to form HBrO, not HOCL. Nice "ah-ah" moment for me, thank-you. Anyway, the sticky also expects this to be a one-time motion, though, and assumes the daily use of a floater and tablets -- which are just sodium bromide + <some form of chlorine>

Don't hold this against me but I've been content with the convenience of one-step "brominating" granules (mixture of sodium bromide and Di-chlor) because I get that at start up you have a chlorine spa until you build up enough salt reserve. For me that is a don't care, and frankly I don't get why the one-step approach gets such a bad rap. My only issue with using "brominating granules" is that towards the end of the drain interval you have a larger-than-necessary bromide reserve, although for all I know the tablets do the same thing. Anyway, I've proven the "reserve" thing by using straight dichlor for the oxidizer which still produces a good HBrO conversion. So: problem solved by using straight dichlor instead of the mixture. I have both in my arsenal.

I'm just not a floater kind of guy. I don't like the risk of high localized bromine concentrations wherever the floater may end up, risking my shell, cover, pillows, etc. and I dont' like things floating around in my tub unless its my grandkids playing with their toys. But it could be that I'm just a control freak lol -- I just don't mind adding the salts and oxidizer myself, vs. letting some compressed form of the same thing dissolve at its own rate.

Actually, Im toying with the idea of a different approach:

1. Adding initial bromide reserve (pure sodium bromide)

2. Shocking with something initially (MPS, Dichlor, Clorox...)

3. using straight on a daily basis, adding more reserve salts only when needed. I guess I don't see the need to add salts every day -- or am I out in the weeds here?

I can use my nose to determine when it is time to add more salts. In such an approach, however, the choice of (daily) oxidizer is interesting: MPS leaves no sanitizer behind (if the reserve is depleted), but Dichlor will. Also, MPS is about $3 a pound and Dichlor is about $7 a pound, but I'm not a chemist: Are these two oxidizers pound for pound equivalent in terms of producing the same amount of HBrO from the same reserve bank?

Liquid Clorox may be cheap, but the risks are way too high (for me) using it as a daily oxidizer. First, there is the chance of spilling on the cover, filters, pillows, or shell. Second, if the bromide reserve is depleted, then you have introduced an unsafe form of chlorine to the spa. MPS and dichlor are much safer choices it seems to me, in this situation.

2. use borax to raise pH instead of Spa up. This is a great tip! It also begs the question: Spa chemical companies re-package baking soda and call it "TA increaser", so why hasn't someone put 20 mule team borax in a 2 lb bottle, tripled the price, and called it "the safer spa up"? Actually, I've used the soda ash by carefully considering the effect on TA as well, but this tip is a great ah-ah moment for me, and I'll probably be adding borax to my arsenal now :-)

Thanks again for the opportunity to join the forum

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The tablets in a floater are not sodium bromide. They are bromine attached to DMH so when the tablets dissolve in water bromine is released. It's somewhat similar to Trichlor tablets, but not as acidic (since DMH and HOBr are not as acidic).

As for your proposed approach, that's fine, but realize that ANY of the oxidizers you talk about -- MPS, Dichlor, bleach -- ALL oxidize bromide to bromine, though MPS is slower in doing so which allows MPS to oxidize some bather waste (if any is present). So with any reasonable bromide bank, you won't have any leftover MPS, Dichlor or bleach -- I understand you did say that the leftover is only if the bromide bank is depleted.

MPS and Dichlor are not equivalent pound-for-pound. In terms of oxidizing equivalence, one pound (16 ounces weight) of MPS is equivalent to 5.8 ounces weight of Dichlor. MPS is generally more expensive than Dichlor, especially if you buy larger quantities of Dichlor (say, a size used for pools). Of course, bleach is the least expensive by far -- the equivalent being 50 fluid ounces of 6% bleach or 36 fluid ounces of 8.25% bleach.

As for using bleach, it would only be too strong (unsafe, as you put it) if you had no Cyanuric Acid (CYA) in the water. If you used Dichlor initially then you would have CYA in the water and the bleach would not produce chlorine that was too strong -- CYA moderates chlorine's strength. That's why the Dichlor-then-bleach method for chlorine uses Dichlor initially to build up the CYA level.

pH Up that is soda ash is of course packaged and sold at much higher pricing than the exact same chemical, sodium carbonate, that is in Arm & Hammer Super Washing Soda (careful: NOT the laundry detergent). Also, borax is also sold for pools as Proteam Supreme or Bioguard Optimizer products at much higher pricing.

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awesome info thanks chem geek. so:

1. With a suitable bromine bank, there is no reason to avoid Clorox. Question: Without having used di-chlor first, is there a risk using bleach if the bank gets depleted?

2. Bromine tabs don't contribute to the bromine bank then, like regular use of the dichlor-salt mixture?

3. check my math here: At 2.75 times the oxidizing strength of MPS, dichlor (~ $7/lb for 5 lbs) is not that far away from the cost of MPS (at $3/lb for 12 lbs), but I do see your point. In fact, for a bromine spa, one wouldn't really need MPS at all, unless you wanted to shock before building up the salt bank.

The last hurdle I have to get over is the handling of the bleach and risks to shells pillows filters, covers etc. seems like you would want to add the bleach to the center of the tub with jets running, but the risk to these elements of the spa is still not zero in the event of a mistake.

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If after a fresh refill you never use Dichlor (or otherwise add CYA to the water), then if you use bleach and there is no bromide left, then the chlorine will be too strong. It's not a disaster, but it will oxidize things faster including your skin, swimsuits, spa covers, etc. The active chlorine level with 5 ppm FC and no CYA in the water is about 8 times higher at hot (104ºF) spa temperature compared to having 40 ppm CYA in the water and it's about 35 times higher at lower temperatures (80ºF) though it's mostly that the active chlorine level with the CYA at the lower temperature is much lower, not that the active chlorine level with no CYA is much higher.

Bromine tabs DO contribute to the bromide bank, but not right away. The bromine tabs release bromine and when the bromine gets used/consumed then it converts to bromide so adds to the bromide bank. Some bromine will outgas and some will combine with organics and not be recovered (some might get filtered out and some may remain dissolved), but most of the bromine will get converted to bromide.

You are correct that you want to pour any concentrated chemical slowly over a circulation flow. If you have CYA in the water, then the risk is lower since the chlorine will bind to CYA very quickly, though it doesn't take very long for the chlorine to react with bromide to convert it to bromine either. Also, bromine itself is not moderated in its strength and is itself harsh on pillows, covers, etc. The greatest risk is from adding a concentrated chemical directly onto such items. You can always dilute a chemical in water if you want, though just pouring slowly over a circulation flow is usually sufficient. Then again, there are many people using chlorinating liquid or bleach for pools who ruin their clothes by getting a drop of bleach on them.

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ok -- right I should have been ablet to see that by adding bromine to the spa, it will contribute to the bank indirectly. But on a related question -- does the effective usable bromide bank actually keep getting larger and larger, or does the bank's effectiveness decay enough to benefit from the continuous addition, either via sodium bromide directly or via bromine? which method (startup + tablets versus one-step granules) will manage the bank most effectively? whats behind my question is the assumption that if the bank is sufficient, or if it is twice as large as necessary it doen'st matter -- the level of bromine will always be determined by the oxidizer. Thus, my other assumption expressed in another thread that the one-step method results in an unecessarily large bank. is that true?

To help tune my understanding of the one-step granular products, what happens in each of the following two cases?

1. you put a small amount of "brominating granules" (approximately 15% sodium bromide, 85% dichlor if memory serves)into the spa after a fresh fill. My assumption here is that the bank is not large enough to form bromine, and you have a chlorine spa at first? thats what my nose tells me anyway :-). or is the chemistry a bit more complex than that.

2. you put the granules into a small glass, and add a cup of water. what is the result? do you have enough salt in the bank to convert all of to bromine or does the high concentration of chlorine via the dichlor still result in a chlorinated solution?

lastly, regarding your statement, "bromine itself is not moderated in its strength and is itself harsh on pillows, covers, etc", my assumption over the last several years is that this is why there is a risk to floating a disolving bromine tablet around the spa - if the floater happens to take up residence near a pillow... ..

or are you simply pointing out that adding bleach to the center of a 500 gal tub is no more risky than operating a bromine spa in general?

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The bromide bank gets larger and larger unless the bromide gets diluted from water dilution or escapes via bromine outgassing or bromine combined with organics in a way they get precipitated. In general, the bromide bank grows if you keep adding bromine to the water via bromine tabs. Note that with ozone, not all bromide is converted to bromine. 23% of it will get converted to bromate so is effectively lost. So without bromine tabs and using only ozone, you will have your bromide bank get lower over time.

You are correct that once you set up an initial sufficiently large bromide bank, then you can always create bromide from it via the oxidizer (though note what I wrote about ozone above).

When you add "brominating granules", then assuming you already have bromide in the water, the bromide from the granules PLUS some additional bromide in the bromide bank get converted to bromine. When the bromine gets used/consumed, it becomes bromide again. If there is not enough bromide in the bromide bank, then some of the chlorine remains as chlorine until it gets used/consumed. So your understanding is correct.

If you put granules into water (presumably without bromide since tap water doesn't have bromide in it, or certainly not much), then the result will be some bromine and somewhat more chlorine. So it's a mixed solution with more chlorine than bromine. Note that the fact you put the granules into a glass is irrelevant -- the same thing happens if you add it to a spa if you never added bromide or bromine to the spa, such as after a fresh refill.

The risk you point out regarding a floater is an additional risk due to higher concentration. What I was pointing out was even without the floater and just maintaining a bromine level in the spa will slowly oxidize items in the spa. Though the same is true for chlorine, having CYA in the water moderates chlorine's strength so that the rate of such oxidation can be somewhat lower than with bromine.

Adding bleach slowly with circulation to water that has sufficient bromide to make bromine is no more risky than operating a bromine spa in general.

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