Sanitation is a very important aspect of hot tubs.

Sanitation is a very important (if not the most important) aspect of hot tubs. Many different solutions exist to keep water sanitized, and new discoveries are made every year. One of them in particular has been overlooked in the past but is starting to gain popularity in the hot tub industry: bromine. Before we go into more detail, let’s take a look at what options are currently available on the market for customers.

What is a sanitizer?

A sanitizer is an agent that will keep your water clean by killing or neutralizing contaminants such as bacteria, ammonia, viruses and other agents which are harmful to humans. They prevent, for example, the spread of diseases and infections, such as E. Coli, Legionnaires’, and Giardia, from other bathers. These agents also help your filter keep your water clear by killing and oxidizing algae. This is an absolutely necessary step to take, especially for hot tubs, as the higher water temperatures offer a great breeding ground for bacteria. Unsanitized, or improperly sanitized, water can lead to severe illnesses, and sometimes even death. Deciding on a sanitizer should not simply be a matter of what is cheapest – it is a decision that needs to be based on the needs of the customer, and what will keep them and their families healthiest. A big family that uses the spa many times a day will have different needs, for example, than a couple who uses it once a month.

Types of sanitizers

Sanitizers can be placed into two main groups: non-residual and residual.


Non-residual sanitizers will only sanitize water when it goes through the system, meaning that in order to be completely sanitized, all the water from a spa must have passed through one particular point in the plumbing. In addition, not all of these systems kill all the contaminants. For both of these reasons, non-residual sanitization is considered strictly supplemental and should be used only in conjunction with a main residual sanitizer. These non-residual systems, such as ozone generators, UV lights, and ionizers, will give users the added benefit of using fewer chemicals.


Residual sanitizers work by building a bank of sanitizing chemical agent in the water. These chemicals stay suspended in the water, ready to act whenever a contaminant is introduced. Contrary to non-residual, where the water may need to circulate for a few minutes before being treated, these chemicals can kill contaminants the second they are introduced. After reacting, a molecule of sanitizer will become spent, requiring the addition of new sanitizer in the water. At the moment, the two sanitizers registered with the EPA (and Health Canada) are chlorine and bromine. Products that do not have to be registered with one of these regulatory bodies may be safe, but will not be strong enough to be effective.


– Advantages: Cheap, easy to find

– Disadvantages: Very volatile, eye/skin irritation, and pungent smell


– Advantages: Softer on the skin and eyes, non-volatile, effective on a wider range of pH and at higher temperatures

–  Disadvantages: Higher price, not for prolonged use in sunlight.


By Pier-Olivier Hamel