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Thread: Where did my Bromide bank go?

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    Where did my Bromide bank go?

    I've been noticing that in many of the hot tubs I regularly maintain, that for some reason, I'm not seeing Bromide being converted back to Bromine like I did in the past. In some tubs that had too much Bromine added in the past, I would see the water turn yellow when I added MPS. In most others, I would see FC show up on a test strip. Lately, I've been noticing that in many of these tubs, neither of these things are happening. When I started noticing this, I filled the floater with bromine tabs and put it back in the tubs, but now I'm noticing the tabs don't seem to be dissolving in many cases. Is it possible that there is just so much to be oxidized in these tubs that the MPS is being occupied by organics so I don't see the Bromide converting to Bromine?
    TreeFiter

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    Saugerties, NY

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    Re: Where did my Bromide bank go?

    That's possible. If you were to add chlorine and found that this produced bromine, then what you wrote may be what is happening since MPS oxidizes bromide to bromine much more slowly than chlorine does, so MPS may oxidize other things first.

    If you find that even adding chlorine that you aren't getting bromine (though I'm not sure how you'd know that since both measure on the tests) then the bromide bank could be used up. This can happen in a spa with an ozonator since ozone not only reacts with bromide to produce bromine, but it also reacts with bromine to produce bromate so eventually the bromide bank gets used up if you don't add more bromine via tabs or add sodium bromide directly.
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    Re: Where did my Bromide bank go?

    None of my tubs use ozonators, so I don't think we are losing bromine as it is converted to bromate.

    Maybe I would be able to tell if bromine is still present if when I add chlorine, I see the water turn yellow. I guess this would only really work in tubs with a rather large bromine bank.

    Any thoughts on why I'm seeing tablets sit in a floater for weeks without dissolving?
    TreeFiter

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    Saugerties, NY

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    Re: Where did my Bromide bank go?

    Well if the water has had a lot of bromine tabs in them, then perhaps the water is getting saturated with DMH which is the leftover from the tabs somewhat analogous to CYA from Trichlor tabs. In fact, very high DMH levels might even inhibit bromine somewhat similar to Trichlor but not as strongly (i.e. it may take more DMH to bind more bromine to it compared to CYA and chlorine).

    The way around this is to use oxidation of the bromide bank as the main way to produce bromine to oxidize bather waste and only use the bromine tabs for background dosing in between soaks so that not as much DMH will build up.
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    Re: Where did my Bromide bank go?

    But even with DMH in the water, shouldn't I still get a test result, much like Chlorine with CYA? For the most part I started pulling out the floaters once I had a good Bromine level, and started relying on a heavy dose of MPS to keep it oxidized. When I figured this out, there were already a few of them that were already overloaded with Bromine, but they always showed the presence of Bromine in some way. Now, out of nowhere, some of them aren't showing me anything.
    TreeFiter

    Pool Technician
    Saugerties, NY

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    Re: Where did my Bromide bank go?

    If the water is saturated with DMH, then the bromine tabs may not dissolve and if they don't dissolve then they won't release bromine and you won't measure bromine in your test as a result.

    IF the bromine tabs dissolve then yes the bromine test measures all the bromine including that which might be bound to DMH because like CYA the bromine would get released quickly.

    The bottom line is that for whatever reason the bromine tabs aren't dissolving, if they don't dissolve then you won't get bromine from them. As for why bromine doesn't show up when adding an oxidizer, that's a separate issue with regard to the bromide bank. To make sure the issue isn't a buildup of organics that MPS is reacting with before producing bromine, you should add chlorine and see if it registers though as I pointed out it's hard to know whether you've got chlorine or bromine (though as you wrote if you add a lot and the water turns yellow in that area, then it may be producing bromine).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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