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RDspaguy

Bromine use in spas

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Bromine has long been the preferred sanitizer for spas/ hot tubs due to it's unique properties. It has a slower dissipation at high temperatures than chlorine, is effective over a wider ph range than chlorine, has less odor and gas-off, and provides a certain degree of sanitation even when combined with organic contaminants. It is less reactive than chlorine, which means it is less irritating to skin and eyes, but works slower at the elimination of contaminants. These factors make it an excellent choice for spa sanitation, but it is important to understand how it works to be successful in its use.

Bromine use requires the establishment of a "reserve" or "bank" of inactive bromine, called bromide, from which active bromine is generated by means of oxidation or "shock". This reserve is established with the chemical sodium bromide, typically in a concentration of 10-15 ppm in the water. From this reserve bromine (hypobromous acid in solution) is formed by oxidation, typically with chlorine, monopersulfate (mps, non-chlorine shock), or ozone, though other oxidizers (such as hydrogen peroxide) will also cause this reaction. Recommended bromine residual is 3-5 ppm for a spa, though those with ozone can be maintained as low as 1ppm. It is important to note that sodium bromide cannot be tested with a bromine test kit or strips.

As bromine combines with organic contaminants, sanitizing the water, it is converted into bromamine, a harsh and irritating chemical. It is also important to note that a bromine test cannot differenciate between bromine and bromamines, so frequent oxidation is necessary regardless of residual test results to avoid irritation of skin and eyes.

Once a bromide reserve is established it cannot be removed by any reasonable means and the water must be drained to change sanitation methods. The addition of chlorine will just oxidize (shock) the bromamines and bromides into bromine without establishing a chlorine residual in the water.

Bromine tablets maintain the bromide reserve and oxidize the bromamine and bromide to generate bromine. Bromine tablets alone will not sanitize the water without a bromide reserve to work with. Bromine tablets are a combination of chlorine and a small amount of bromide to maintain the reserve. Bromide reserve decreases from dilution as water is added to make up for carry-out, or is dissipated slowly from uv (sunlight) and ozone exposure. Many bromine users do not use tablets and rely on manual addition of oxidizers for bromine generation, and sodium bromide for reserve maintenance. If using tablets, a weekly shock is recommended. If manually oxidizing only, treatment after each use is recommended at a minimum of once per week.

So, in summary, you first establish a bromide reserve of 10-15 ppm using sodium bromide, then oxidize with chlorine or mps to establish a bromine residual of 3-5 ppm (1-3 ppm with ozone), then shock frequently and maintain that residual with oxidation and, if you choose, tablets and/or ozone.

Here is an article from an industry publication if you want to study bromine maintenance further.

https://aquamagazine.com/features/bromine-chemistry-for-spas-and-pools.html

 

 

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