By Pier-Olivier Hamel
Pure bromine is a chemical element in the halogen family. Its chemical properties are similar to chlorine’s, except it is a liquid at room temperature instead of a gas. This results in a much more stable sanitizer that does not evaporate and is effective at higher pH levels, making it ideal for hot tubs. For example, at a pH level of 7.8, bromine still has about 85% of its efficiency and chlorine is under 30%, which means that bromine users don’t have to monitor and adjust their pH as strictly for the sanitization to be effective.
However, bromine does not do well with prolonged exposure to UV light, as the UV light breaks it down. This same process happens with chlorine, as well, which is why chlorine is used with a stabilizing agent. What this means is that bromine is best suited for covered or indoor applications.
Granular BCDMH (bromo-chloro-dimethylhydantoin)
Just like traditional chlorine, Bromine can be introduced to the water in the form of granules, powder, or even liquid. These products are very common under many different brands and can be found at almost every hot tub dealership. These "hockey pucks" contain part bromine and part chlorine (which is used as the oxidizer to activate the bromide). Users simply add the required quantity of BCDMH into their tubs in order to build the required bank, and then maintain it. This type of product requires regular addition of chemicals in order to keep enough residual sanitizer. Along with having to be present on the site regularly and take the time to add chemicals and re-balance the water, the residual build up from frequent topping up may increase scaling and could cause skin irritation, requiring more frequent dumping of the spa water.
Bromine generators are electronic devices that automatically generate bromine into the water. They are also commonly referred to as bromine salt systems, not to be mistaken with chlorine salt systems, which are chlorine generators.
These systems are installed in the plumbing (usually after the heater) of the spa and send a small electrical charge through the water as it passes through conductive plates in the device’s reaction cell. Pure sodium bromide, commonly called bromine salt, is added once to the water, where it separates into sodium ions and bromide ions. These ions alone have no power of sanitation at all, but in contact with the electrical charge the bromide ions absorb the energy and transform into available free bromine. The free bromine, or just bromine, then becomes suspended in water, ready to react upon contact with any contaminant or impurity. When this reaction occurs, the unwanted particle gets neutralized and the bromine goes back to being a bromide ion. This means that with these devices bromine is infinitely recyclable and the sodium bromide should never get depleted unless physically removed from the spa. Because bromine does not evaporate, sodium bromide only needs to be balanced after significant water loss (splash out or draining).
While these systems have higher initial costs, they provide many benefits to their users, such as eliminating the need to add additional chemicals for sanitation. Water parameters will also be less affected over time, thus reducing the need for regular balancing. As a result, water will not only be softer, but will also stay this way for a longer period of time. All of this makes for a very low-maintenance system that keeps the spa clean at all times, whichis great, for example, for people with cottage spas. Also, as opposed to BCDMH, these devices produce entirely chlorine-free spa water. Finally, bromine generators only make bromine when there is water flowing, requiring usually at least 8 to 12 hours of run time per day. Therefore, they are best used with a circulation pump in hot climates.