# Thread: Bromine spa regular oxidizer amounts

1. ## Bromine spa regular oxidizer amounts

From the sticky, @chem geek said:
Code:
```How do I use Bromine in my spa (or pool)?

You could just add some bleach or MPS, up to you (bleach is less expensive, of course).  Each fluid ounce of 6% bleach in 350 gallons would increase the bromine level by around 3 ppm.```
Can I calculate my oxidizer amount linearly based on this? For example, I have 10% bleach and a 220 gallon tub, so if I say .06 "oz units" of chlorine per 350 gallons is equivalent to .0377 "oz units" in a 220 gallon tub, then .377 oz of 10% should raise my tub 3 ppm of bromine from my bromide bank. Is that true? And if I divide by 3, then approximately 1/8 oz of my 10% in my 220 gallon tub converts bromide to bromine at 1 ppm?

Also, with OTO, after adding bleach, will my reading be total bromine + chlorine until the conversion is complete? About how long does the conversion take (minutes, days?)?

Does the chlorine FAS-DPD (R-0871) test show me only chlorine?

The addition of borates made an instant improvement. I highly recommend it. The water is "sparkly" and feels better. And getting the TA just right so that the pH stays constant has made everything so much easier. Thanks for the guidance TFP!

2. ## Re: Bromine spa regular oxidizer amounts

I believe your calculations are correct, but you can use PoolMath to figure it out. Just plug in your numbers for 10% LC and for every 1 ppm FC it will add 2.5 ppm Br.

The OTO will show the total of both but the conversion is quite fast. I would call it minutes at most.

The FAS-DPD will show total bromine I believe, which is what you want. Someone will correct me if that is not entirely true. I personally just use OTO when I check a spa.

3. ## Re: Bromine spa regular oxidizer amounts

To use FAS-DPD for bromine multiply the end result by 2.25.

Before my recent drain/fill, when I shocked my bromine spa w/ 12.5% chlorine, it would increase/shoot up my bromine level for multiple days. Again, on my prior old water, I would shock 1x/week w/ 75 ml 12.5% chlorine and this was for a 300 gal. spa. If I recall correctly, I think my bromine level was >10 for at least 2-3 days. But, this was without usage of the spa. Not sure if any of this helps you.

4. ## Re: Bromine spa regular oxidizer amounts

Originally Posted by bbrock
Before my recent drain/fill, when I shocked my bromine spa w/ 12.5% chlorine, it would increase/shoot up my bromine level for multiple days.
Thanks bbrock. That's what I was expecting. But it would drop right away. I think my 'free, used' hot tub had some goo in the tubes. It's holding now but on the next drain it's getting ahhhhh-some.

On that note, a free hot tub is worse than a free puppy. Seriously would have been better off purchasing this thing new.

5. ## Re: Bromine spa regular oxidizer amounts

Free... yeah I would be a little concerned about what's lurking in that plumbing. I just used Ahh-Some on this current drain/fill. That stuff got things out I don't even know were in there... such as that missing sock I haven't been able to find.

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