No way to test bromine bank?

[Malka]

I do partial top up fills of a few gallons 1-2 times a week. How can I know if my bromine bank exists?
Testing after Cl shock will tell me about the chlorine I added. MPS shock also interferes with the sanitized testing.
I added startup level granulated bromine when I changed the water last month. How can I know what’s there now?

 

[JoyfulNoise]

Bromine can not be tested independently of chlorine with the simplistic chemical tests available for pools and hot tubs. If you added the correct amount of sodium bromide to your tub, then it is always there unless you exchange tub water with fresh water (evaporation doesn’t change bromide levels). When you test sanitizer levels, you simply assume that your sanitizer is all bromine because the oxidation of bromide to bromine by chlorine is a fast and complete chemical reaction. Ozone and MPS will increase the amount of bromine formed and, as you know, MPS will interfere with the DPD-FAS test unless you use the deoxidizer reagent to separate out the MPS interference.

 

[Malka]

Got it. Thanks!