Can Bromine tabs labled for pool be used in a spa?

[itsnaturesway]

I am trying to cut costs by buying bromine tabs in bulk. My local Costco has a larg pale of Bromine tabs for pool, the guarantee available bromine on the lable is close to the tabs i am currently using in my spa.

Pool tabs: Available bromine present as 1-bromo-3-chloro-5.5-dimethylhydantoin......61% Available chlorine, present as 1-bromo-3-chloro-5.5-dimethylhydantoin....27%

Spa tabs (Omni for hot tubs and spas): Available bromine present as 1-bromo-3-chloro-5.5-dimethylhdantoin.....64% Available chlorine present as 1-bromo-3-chloro-5.5-dimethylhdantoin.....28%

Can i use the pool tabs for spa and is there a shelf life on bromine tabs?

 

[chem geek]

Welcome to TFP!

So long as the pool tabs don't have some other ingredients you don't want, they should be fine for use in your spa. It's possible that they are using different binders in making the tabs and that they dissolve at a different rate, but most likely they are the same. Check the full ingredient list. If you give us the full name and manufacturer of the pool bromine tabs, we may be able to look up an MSDS for more info.

Pure BCDMH would have (2*35.453)/241.47 = 29.4% Available Chlorine and (2*79.904)/241.47 = 66.2% Available Bromine so it looks like the pool bromine tabs are 92% pure BCDMH while the spa tabs are about 96% pure BCDMH.

 

[marty]

Sorry to hijack but just curious, why would anyone want bromine in pool? from reading here i thought bromine was strictly for spas due to higher temp + you couldn't shock pool if needed.
Plus tabs have cya, and since spa is coverd, that wouldn't be necessary...

 

[chem geek]

Sorry to hijack but just curious, why would anyone want bromine in pool? from reading here i thought bromine was strictly for spas due to higher temp + you couldn't shock pool if needed.
Plus tabs have cya, and since spa is coverd, that wouldn't be necessary...

Bromine tabs do not have CYA, they have DMH. It is true that Trichlor tabs are not normally used in spas because they dissolve too quickly (so add too much chlorine too quickly) and their acidity tends to throw off the pH in a spa faster because it's such a small volume. There are special slow feeders and Trichlor tabs for spas such as what AquaFinesse® provides, but they are uncommon.

It is not exactly true that bromine is more stable in a hot spa than chlorine. If one does not use CYA, then chlorine does outgas faster than bromine (so gets used up faster), but with CYA in the water chlorine outgasses somewhat more slowly than bromine so lasts about as long, but having bromine tabs means bromine is continually added to maintain bromine levels. Bromine can be used in pools, but because it does not bind to CYA there will be more of it that gets lost to sunlight. It's also more expensive than chlorine so for pool volumes it can be expensive. Nevertheless, some people who use a sodium bromide product as an algaecide have their chlorine pools turned into a bromine pool for a while (depending on how much they use).

You can shock a bromine pool, but usually because bromine isn't moderated in strength by CYA, you won't get algae, but bromine doesn't oxidize the same chemicals or as well as chlorine so shocking with chlorine is sometimes needed. This is most commonly seen in bromine spas where one uses bromine-only tablets (DBDMH) where periodic shocking with chlorine helps to keep the water clear.