Hot tub confused me a bit

[bolleat]

I have been doing great with BBB for my pool, but my Sundance hot tub has got me a bit confused.

It is a Bromine System. Floater with bromine tabs, chlorine shock.

Current readings:
Ph: 7.4
TA: 50
Total Bromine: 20 (used K-2006 kit, 10ml water multiplied drops by 1.125)

I added shock on Sunday, now TB is 20. Also I feel like sometimes the Bromine tabs in the floater all of a sudden dissolve quickly while other times they melt slow like they should. Am I crazy?

My wife got a very mild case of hot tub folliculitis (at least that's what I think it is, I am actually a doctor) so I want to make sure I am doing a good job with sanitation. I was hot tub guy'd and using test strips until recently. Now I am getting things on track thanks to TFP.

How do you know if you have a bromide reserve?
How do you know if you need to shock sooner, or later than just once per week? Are there parameters to monitor?

 

[chem geek]

To ensure you have a bromide reserve, you would normally add sodium bromide initially on a fresh fill of water. The usual dosage is 1/2 ounce per 100 gallons which is 37.45 mg/L of sodium bromide so equivalent to 58 ppm bromine (that's the capacity if all of it were activated). After that, if you are using tabs, then the bromide bank should increase over time. There is no easy way to check it since the test kit cannot readily distinguish between chlorine and bromine (there is a way to tell, but it involves using ammonia and is complicated).

With bromine, once a week shocking using chlorine is usually sufficient. It's not for disinfection, but to help oxidize bather waste since bromine by itself usually isn't enough to keep the water clear and chlorine helps oxidize some chemicals either completely or so that they get more readily coagulated and filtered.

If you were keeping the bromine level up and never let it get very low -- never below 2 ppm for example (normal minimum target for bromine is 4 ppm) -- then the tub should have been disinfected properly. Take a look at this link that helps to distinguish between a chemical reaction (or heat sensitivity) vs. a bacterial infection. There's a joke about dermatologists where treatment is "if it's cold, heat it; if it's hot, cool it; if it itches, use a corticosteroid". I've got a skin condition being treated (combination of Grover's disease and pityrosporum folliculitis) so get to hear the jokes different doctors use referring to each other's specialties.