Testing Bromine with TF100 FAS/DPD

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wes8398

wes8398

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Sep 23, 2009
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Question ... when I test my brominated hot tub water with the FAS/DPD test, is there some finagling I have to do with the number I get in order to "correct" for Bromine (since it's a Chlorine test)? I think I'm getting a little confused from reading things like "10ppm bromine sanitizes like 5ppm chlorine" and so on.
So, for example, it took 20 drops to turn the pink test water to clear tonight. Does that mean I have 10ppm of total bromine? Or does it mean that I have 25ppm total bromine (since I read somewhere that you multiply the chlorine test by 2.25 to get your bromine reading)?

Confused....
 
Yowza ... so now I'm left wondering why my bromine is so high. I'm not entirely sure if my tub (purchased used, about a year old) has an ozonator or not, so maybe that's the problem. I've been leaving a floater in the tub too, so maybe that and the ozonator are causing the high reading. Reason I'm assuming that I do have an ozonator is because when I had all the side panels off the tub to add some insulation around it, I noticed a small plastic box mounted to the frame which said something about ozonator. I wasn't sure that was 'the' ozonator because it was so small though - only about the size of a wallet. That must've been it...
 
You can use the R-0871 and correct for the small difference, which really is no big deal. For a 10 ml sample size, each drop is 1.125 ppm bromine while for a 25 ml sample size each drop is 0.45 ppm bromine. If you had the R-0872 then it would be 1.25 ppm and 0.50 ppm so really not that much of a difference.

Note that the test is measuring Total Bromine and there is no need for the R-0003 reagent. Combined Bromine is automatically measured in the first part of the test since monobromamine is in equilibrium with a more reactive monobromammonium ion that reacts with the dye in the test. It is this reactivity that makes the combined bromine still effective as a disinfectant (though monobromamine can smell if it gets high enough in concentration).
 
So for the most part I can follow the same instructions. Amazing. I have been trying to find the best place to get the R-0872 for about a week now.

For the quick test for bromine though... I have both the oto and DPD drop tests. Which tends to be better? I think I can see the differences on the oto but I though the DPD was supposed to be more accurate.
 
OTO is best for checking for zero/non-zero sanitizer levels. The shades of yellow all tend to look the same between 3 and 8. DPD is prone to getting false zero readings when the sanitizer level is too high, but is much better at distinguishing between 3 and 5 and 8.
 
i am trying to get a routine for testing. but I wind up testing with the FAS-DPD test almost every time anyway. I get OCD about testing and I am sure I overtest. I have all three tests but the OTO and DPD drop tests are both just about out and I am trying to figure out what to reorder. I have a salt system for the pool and use bromine in the spa.
 
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