They are a little hidden in the
Further Reading link in the
Pool School, but they are also stickies in this
Spa and Hot Tubs forum. There is
How do I use Bromine in my spa (or pool)? and
How do I use Chlorine in my Spa (or pool)?.
Is there anything different with Bromine vs all of the articles on Chlorine? Other than the fact that you don't use CYA.
Yes, when bromine gets used up it becomes bromide ion that can be reactivated with an oxidizer such as chlorine or non-chlorine shock (MPS) or ozone. With ozone, some of the bromide can become bromate so can get used up faster than oxidizing with chlorine.
Bromine combined with ammonia will still register in a Free Chlorine (FC) test so one just reads Total Bromine and doesn't try and distinguish free and combined bromine. Monobromamine is still a reasonable disinfectant (see
this link for more technical info).
And yes, bromine doesn't combine with CYA so the CYA level in the spa isn't relevant (it can still build up if using Dichlor to activate bromide to bromine, but this CYA build-up doesn't matter in a bromine spa).
I use Spa Shock granules about once a week. Is this a good idea? Should I just use plain Cl instead?
Spa Shock chlorinating granules are probably Dichlor (or a mix of Dichlor and sodium bromide), but you can use bleach if you want. Just note that Dichlor is net acidic when accounting for chlorine usage/consumption so if you switch to using bleach you may need to lower the TA level to have the pH not rise over time.
I empty, clean and refill the spa 3-4 times per year. Is that about right?
This depends on your bather load. The rough rule the spa industry uses is a Water Replacement Interval (WRI) = (1/3) x (Spa Size in Gallons) / (# of Bathers per Day) where it seems they assume 20 minute soaks so this is (1/9) x (Spa Size in Gallons) / (# of Person-Hours per Day)
This same formula roughly applies to Dichlor-only chlorine spas. With the Dichlor-then-bleach method, one can usually double the time between water changes because chlorine keeps the water in good shape better than bromine and using bleach prevents the build-up of CYA which does affect chlorine.
When I empty the water I hose down the filter cartridges. Should I be using Filter Brite or something like that to clean them?
If you suspect biofilms or want to be more thorough, you can use
Ahh-Some for the filter and for the piping and other spa areas you can use
Ahh-Some for that as well. When people use it, they get a lot of junk come out, but in a properly maintained spa it's probably accumulation of body oils rather than biofilm. Another approach for cleaning cartridge filters involves TSP and is described in
Cleaning a Cartridge Filter (the chlorine instructions also apply to bromine spas).
Do I need to be concerned about TA levels? What about CH?
Because spas typically have hot water and have more aeration including aeration jets, the rate of carbon dioxide outgassing is higher and therefore the pH tends to rise unless you use acidic chemicals. Bromine tabs are acidic and Dichlor is net acidic and non-chlorine shock (MPS) is quite acidic so you just have to get the TA to whatever level where the pH is reasonably stable. For chlorine spas after switching to bleach, the TA usually needs to be lowered to no more than 50 ppm and the use of 50 ppm Borates for additional pH buffering is recommended.
For CH, you have to be careful not to get it too high because the higher spa temperatures make calcium carbonate scaling more likely. 120-150 ppm CH is usually enough to reduce or prevent foaming and not be too much to make the saturation index too high. Most spas are not plaster so have no need for CH other than to prevent foaming (and technically magnesium would also prevent foaming).
I assume that the aeration from the jets will increase pH - is that correct? If so should I be regularly adding MA to decrease pH?
Yes, as I described above. Only add MA if the pH is in fact rising, but if you get the TA lower you may get to a point of reasonable stability of pH if you are using bromine tabs or activating bromide with Dichlor or MPS (as opposed to bleach, though that's a lot less expensive).
How often should I change the cartridge filters?
Not sure. Probably when they wear out so that they have holes that allow water to bypass.
My spa generally foams a bit - why is this? Is this an issue? I don't mind and the kids like it.
Foaming comes from soap-like substances so usually from the people using the spa who don't rinse themselves or their swimsuits enough before getting in. If the CH level is too low, then more foaming can occur. Calcium and magnesium inhibit foaming by combining with soap chemicals precipitating them (such as soap scum).
Occasionally my FC/FB level tests very low, even though the Br dispenser is open and the Br is dissolving on a regular basis. Why is this and should I be concerned? I normally add Br granules when this is the case.
You probably aren't adding enough oxidizer after your soak, especially when the bather load is higher. The bromine tabs are usually just to provide a background dose in between soaks and you add an oxidizer after your soak in proportion to your bather load. The same rough rule-of-thumb applies to bromine spas as chlorine spas in that in those without ozonators, for every person-hour of soaking one needs roughly 3-1/2 teaspoons of Dichlor or 3-1/2 fluid ounces of 8.25% bleach or 7 teaspoons of non-chlorine shock (43% MPS).
What is a bromine bank that I have read about elsewhere?
It's a bromide bank which is created initially by adding sodium bromide but also accumulates from spent bromine from bromine tabs that gets used/consumed. When you add an oxidizer to the water, it will convert bromide ions to bromine (hypobromous acid).
