Chlorine vs. Bromine in Pools and Spas

Water-recreation facilities are a real boon to any athletic club. From providing a hot, relaxing soak after a workout to enabling competition-level training, pools and spas round out the options at your favorite gym. While the use and enjoyment of these facilities should be easy and care-free, there are several aspects to the maintenance and operation of a pool or spa that are critical to bather health and wellness. The purpose of this article is to address the importance of sanitizer in the water, and to discuss the differences between the two most commonly used sanitizers, chlorine and bromine.

Sanitizer, for the purposes of pool and spa chemistry, is any chemical that kills or inactivates germs, viruses and bacteria in the water. Proper maintenance of sanitizer levels is how you avoid catching the cold that the other person in the spa with you has. Chlorine and bromine belong to a class of chemicals called halogens, which work by forming acids in the water that attack and kill microscopic water-borne organisms. As the sanitizers do their work, they become gradually less effective, necessitating the constant renewal of their levels in the pool or spa water. As the water undergoes this cycle of sanitization and renewal, there are some differences between the way chlorine and bromine interact with the water chemistry.

While the chemical reactions can be fairly complex, the end result is simple: properly maintained, sanitizer in a pool or spa creates a hygienic bathing environment. For the user of a water-recreation facility, there are very few noticeable differences between chlorine and bromine. One of the biggest differences is odor. As chlorine becomes “dirty” by binding to contaminants and organisms, it produces the distinctive chlorine smell that many people associate with public pools. Contrary to intuition, being able to smell the chlorine is not an indication that a pool is highly sanitized; in fact it is a good sign that the levels may need adjustment. A properly maintained chlorine-sanitized pool will have little to no chlorine smell, as the form of chlorine that does the work has no odor.

Bromine, on the other hand, has very little odor even when “dirty,” this is one reason why it is often preferred for spas, where the concentrations of contaminants can be much higher. What odor bromine does have, however, is much harder to shower off. Bromine is also more complicated to use, requiring additional chemical processes to maintain its effectiveness. For this reason, it is more costly to operate and maintain a bromine-sanitized pool or spa.

Most frequent users of water-recreation facilities have experienced a rash at some point after bathing, particularly individuals that use a number of differently maintained facilities. This has led many bathers to speculate upon possible chlorine/bromine allergies or reactions. The truth is that, while some individuals are especially sensitive to chemical irritants, actual allergies to halogens are extremely rare. The vast majority of rashes that develop after use of a pool or spa are a skin condition called folliculitus, caused by a variety of Psudomonas bacteria. This results from improper maintenance of sanitizer levels in the water, and the particular type of sanitizer used has no bearing on whether a rash develops. If you should ever develop a skin condition after using a pool or spa, notify the facility’s operator.

At the Seattle Athletic Club, we use chlorine exclusively to sanitize our pool and spas. The primary reason that we use this method is simplicity: with fewer chemical reactions to undergo and less equipment to fail, it is comparatively easy to ensure that safe sanitizer levels are maintained at all times.

While there is more risk of developing a noticeable odor with chlorine, we feel that the advantages over bromine outweigh this potential pitfall. Additionally, as mentioned above, chlorine does not produce much smell when the levels are maintained correctly, and the daily attention paid to our pool and spas by the Facilities staff is more than adequate to prevent a buildup of the “dirty,” smelly type of chlorine.

In summary, selection of a sanitizer is a choice that must take into account many factors, not all of which are detailed in this article. The end result for the bather should be the same regardless of which chemical is used: a safe, hygienic bathing experience. The real key to a clean, odor-free pool is diligent attention by trained, certified and knowledgeable staff.

Written by Matt Wolff, NSPF C.P.O.
Facilities Director, Seattle Athletic Club Downtown