Silly question

[bubbles]

So I have the TFP 100 test kit and have become almost a pro at keeping sparklypoolitis envy across the neighborhood ( had 3 neighbors ask me who my pool guy was!). Now I am finally getting to know my hot tub and and trying to figure out bromine levels...
I use the basic taylor kit for that test but how do people know exactly what the bromine and FC levels are...the little yellow boxes give a range, am I missing something?
I just did the bromine starter and I know it's supposed to be 30 ppm but don't really know how to make sure. Help!!
Thanks,
B

 

[chem geek]

You can't accurately know the level using the OTO test (shades of yellow) for sanitizer level. If you want a more accurate reading, you can use the FAS-DPD chlorine test, but just multiply your FC result by 2.25 to get total bromine. There is no need to do the CC part of the test. So if you use a 10 ml sample size, then every drop is 1.125 ppm bromine (with the 25 ml sample size, every drop is 0.45 ppm bromine). So with a 10 ml sample size, 30 ppm bromine would take around 27 drops of FAS-DPD titrating reagent to turn the sample from pink/red to clear (after adding DPD powder first, of course).

 

[JamesW]

I just did the bromine starter and I know it's supposed to be 30 ppm but don't really know how to make sure. Help!!

I think that you might be confusing bromide and bromine. The starter kit adds 30 ppm bromide. You keep your bromine closer to 3 to 5 ppm.

 

[PaulR]

The initial dose of sodium bromide is just to create a bromide reserve, and doesn't need to be particularly precise. Recommended amount is 1/2 oz per 100 gallons; my local place has 2-oz packets and I just dumped it all in even though my tub is in the 300-350 gallon range.

Your OTO or FAS-DPD test doesn't measure bromide (reserve) anyway, it is measuring the active sanitizer (hypobromous acid) which everybody just calls "bromine."
--paulr