Bromine Mystery

[tub by the lake]

Thanks again,
Our tub is kept at 99 degrees, which is as warm as the kids like it. Thinking about your 5 oz. rule, I went with just 4oz. the first time and the bromine level went to over 13, so I used just 2 oz. the next time and it went to about 7. I don't know how well the rules of thumb work for little kids, they don't have much surface area, but I think more than make up for it in other ways! I'm surprised though that given the 5 oz. suggestion I'm getting away with so little bleach. With the floater in, there must always be some bromine being generated, so I'd think that after a long period, there must be enough introduced to get to the ammonia, and that if I have a bromine test level 4 or 5 days later ( on returning to cabin) it should be mostly bromine by then no?
So my plan is to add the bleach after use (trial and error to find amount), and then try and stick around for at least an hour before testing and see levels of say 6 or so, and then leave the floater in when we are gone. If I see 3-4 on the test when I get back and the water is clear and doesn't smell bad, then that's probably as good as I'm going to be able to accomplish. Does this sound reasonable? What would you expect this to do to pH and alkalinity? is there a predicted direction of change, or do you just need to measure it each time and see?
Larry

 

[chem geek]

You sweat less at 99ºF so it's reasonable to assume that you will need less than the 5 fluid ounces of 6% bleach per person-hour. The little kids sweat less as well, though as you point out they may urinate more, though probably not (if you've trained them well!).

Anyway, your plan sounds fine and yes, the floater is normally set to a low setting just to give you a residual when you aren't using the tub. It's the bleach you add after each soak that should handle your bather load. It does sound like you've now probably caught up.

 

[chem geek]

Some bromine outgasses and some is carried out with water but normally you don't need to keep adding to your bromide bank, especially if you use brominating tabs to maintain a bromine level. So with your floater, you don't really need to add brominating concentrate after the initial dose (assuming it's large enough to get started). It won't hurt since it's just a salt, but it's not necessary.