A week ago I drained my hot tub. I did the whole decontamination method. Cleaned out the pipes, drained, superchlorinated, drained, re-filled and did the 3 step bromine method. My water looked better than ever and my bromine levels were more stable than ever before.

Last night I had a bunch of people in my hot tub and this morning when I tested the water the bromine level was 0. I decided to really give it a good shocking so I added about 12 ounces of 6% bleach then left it covered. I tested it about 7 hours later hoping it would be under 10 so I could use it, and found the bromine level to be at 1.5. This really surprised me as I just dumped in a lot of bleach.

I just added another 8 ounces of bleach and I'm going to go test it in a couple hours, but I have a couple questions.

The bromine levels likely sat at 0 overnight after everyone got out. Does this mean I now have a little bug growing in my hot tub that is eating up all my bromine? If so, can I kill it by continuing to shock until the levels stabilize again? Or is it more likely there was just so much sweat/oils/urine etc. (I hope no urine, but you just never know when people are drinking) that the chlorine I dumped in initially had to kill all that which is why it got used up so quickly? The water was cloudy but seems to be mostly clear again. I don't have to drain and re-fill again do I?

I know the problems with leaving bromine levels at 0 for any period of time, but when you get out very late at night and you've been drinking, you don't always think responsibly.

It's probably just regular oxidizer demand. Every person-hour of soaking in a hot (104ºF) 350 gallon tub requires about 16 ppm bromine (around 7 ppm chlorine) to oxidize the bather waste. Some of this will come from your floater, but not very much. If you have an ozonator, then it may take care of around half this amount in 24 hours.

If your tub is 350 gallons, then the 20 ounces of 6% bleach you added should have been around 28 ppm FC or 63 ppm bromine. That sounds like it should have been enough since that would cover around 4 person-hours. I also assume you are using a FAS-DPD test kit since the DPD test will bleach out at high sanitizer levels making you think they are low when they are actually high.