Spa: bromine or active oxygen, which to choose?
A spa’s hot water pushes disinfectants hard. Bromine and active oxygen are the two most common options, with opposite logics: stability and consistency for one, gentleness and frequent renewal for the other.
In short
Bromine resists heat well and stays effective even when the pH rises: it is the reference disinfectant for a regularly used spa, with a target of 2 to 4 mg/L. Active oxygen is gentler and odourless, but less lasting: it needs frequent renewal and often an activator. It suits occasional use or sensitive skin.
Bromine: stable and consistent
In a spa at 35–40 °C, bromine keeps its effectiveness where chlorine degrades fast, and it tolerates a slightly high pH better. Kept between 2 and 4 mg/L, it provides continuous disinfection with little supervision. It is the most reliable choice for a spa used several times a week.
Active oxygen: gentle but volatile
Odourless and pleasant on the skin, active oxygen is appealing, but it dissipates fast: it must be renewed every few days or after each heavy use, often with an activator. It suits occasional use or a supplement, less a heavily used spa.
What to do, step by step
Assess how often you use it
Spa used often: bromine, more lasting. Occasional use: active oxygen may be enough.
Watch the pH
Bromine tolerates a slightly high pH better; with active oxygen, keep the water well balanced.
Plan for renewal
Active oxygen is renewed often, usually with an activator; bromine lasts longer.
Keep the filter and water clean
Whatever the disinfectant, a clean filter and timely water changes remain essential.
Frequently asked questions
Does bromine smell less than chlorine?
Yes, bromine gives off less odour, especially in hot water, and tolerates a slightly high pH better — two reasons for its popularity in spas.
Does active oxygen really disinfect?
Yes, but less lastingly: it acts strongly then dissipates fast. It suits occasional use, often backed by an activator, less a busy spa.
Can you switch from one to the other?
Yes, usually after a water change, to start fresh. Avoid mixing the systems without an intermediate water change.