Bromine vs Chlorine

chlorine vs bromine

Bromine or chlorine: what is best for my pool and hot tub?


If you have a pool and then decide to get a hot tub or spa, you may think you can use the same chemicals. Well you can but the question is should you, use pool chemicals for your spa and vice versa.

Both of these products are similar and behave in similar ways to sanitise and protect but they do their best work at different temperatures and pH levels.


Bromine is more active in fighting bacteria at high pH levels that are often associated with hotter water found in spas and hot tubs. At a high pH of over 8, chlorine is almost inactive although your test kit will say there is sufficient amount for the job. Most pools run at a pH less than 8 so chlorine can handle the job well. Bromine is not as stable as chlorine when exposed to direct sunlight. As most spas or hot tubs are covered when not in use or inside this won’t matter. Bromine can be stabilised by adding cyanuric acid. And bromine can be reactivated by adding small quantities of MPS shock or chlorine shock. Once the dose of chlorine has killed the bacteria it becomes inert and can’t be reactivated. This can mean that you are less bromine and it may be the cheaper option in the long run.


Chlorine is better at getting rid of and killing algae fast but bromine is fast to kill viruses and bacteria quickly especially at higher temperatures and pH levels. Bromine will continue to clean and sanitise long after chlorine has been exhausted.


Bromine vs. Chlorine



  • use if pH levels higher than 8
  • more suitable at higher temperatures
  • more expensive and need to use more in a swimming pool than chlorine
  • can be reactivated
  • less smell and less irritating to eyes and skin
  • effective over a wider range of conditions
  • better for hot tubs and spas and heated pools



  • use if pH between 7.2 and 7.8
  • it costs less
  • clearer water quality
  • can have a shorter shelf life
  • smells like bleach and can be an irritant if too much is used
  • better for cold water pools

A note for owners of salt water pools


As these pools can run at a higher pH many people opt to use bromine instead of chlorine to sanitise the water. In this case it doesn’t matter if the pH creeps over 8 you know your pool will be safe for the family to use.




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