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Pick a Side

Chlorine vs. bromine: What’s your preference?

Everyone has a preference in competitive markets: Burger King versus McDonald’s, Walmart versus Amazon — and in this industry, the brand of pool equipment you install and the sanitizer you recommend to customers. In the world of chlorine versus bromine, the competition is likewise fierce.

What’s the difference?

You can’t have a good matchup without a little back-story on the competitors. Terry Arko, recreational water specialist at NC Brands (makers of Natural Chemistry, SeaKlear and Coral Seas pool and spa products) has spent 40 years in the industry, has written more than 100 articles on pool and spa water chemistry, presents on the subject at trade shows, is a certified instructor with the National Swimming Pool Foundation and is serving on the Recreational Water Quality Committee for the Association of Pool and Spa Professionals.

Arko notes that chlorine and bromine are both halogens, meaning formed from salt — chlorine from sodium chloride and bromine from sodium bromide. Both are FDA approved disinfectants that have the ability to kill disease-causing organisms, oxidize nonliving contaminants and leave protective residual in the water. Chlorine’s primary killing agent is hypochlorous acid (HOCl) and bromine’s is hypobromous acid (HOBr).

The main difference between chlorine and bromine is the percentage of killing agent in the water based upon the water’s pH, Arko explains. “For example, at a pH of 8.0, there would only be 24 percent active HOCl in the water, but a pH of 7.2 has 66 percent HOCI in the water,” Arko says. “The production of the killing agent for bromine, HOBr, is nowhere near as contingent on pH as chlorine. For example, a pH of 8.0 would be 83 percent HOBr and a pH of 7.2 has 96 percent HOBr in the water.”

Chlorine requires the addition of cyanuric acid (CYA) — 30 to 50 ppm — otherwise, up to 50 percent of residual chlorine is destroyed by UV light from the sun in less than an hour, according to Arko. With proper levels of CYA, the chlorine residual in a pool can last three to ten times longer. Alternatively, sodium bromide requires an oxidizer — potassium monopersulfate (MPS) — to create active bromine. UV light degrades both chlorine and bromine, but CYA will not prevent the degradation of bromine like it does for chlorine. The difference is the temperature of the water.

“Chlorine consumption and ability to hold residual becomes compromised at water temperatures above 85 degrees,” Arko says. “Bromine [on the other hand] has the ability to hold a residual at water temperatures up to 104 degrees.”

Whose side are you on?

John Bokor, regional sales manager for Haviland, says the choice between chlorine and bromine all depends on the application. “A lot of times, in residential outdoor applications, the preferred method [of sanitizing] would be some type of stabilized chlorine,” he says. “As the pH of the water changes, chlorine can either become hyperactive or slow working. Bromine, on the other hand, has a much wider range so the consumer can actually make some mistakes and still have a safe swimming environment.”

Bill Drakeley, managing member of Drakeley Pool Company in Bethlehem, Connecticut, recommends staying away from bromine. “It kills pH [of the water] and damages equipment,” he says. And Luke Pool Service in Alpharetta, Georgia doesn’t even have experience with bromine, according to president Luke Norris. “We only do chlorine,” he says.

However, Tom Landi, president and owner of Landi Pools and Games in New Jersey, has been recommending bromine over chlorine to his customers for the 22 years Landi Pools has been in business. While he acknowledges the cost of bromine is a deterrent for some, he justifies it to his customers because they’re not adding other chemicals.

“With chlorine, you have algaecide, other byproducts and clarifiers that you’re using to enhance the water clarity along with the chlorine,” Landi says. “It isn’t healthy for the swimmer in the long run. With bromine you can pretty much get by with maintaining the proper levels with the water flowing through the bromine feeder and limiting your shocking.”  

Raven Hollingsworth, warehouse and inventory manager for Lake Air Pool Supply in Waco, Texas, agrees that chlorine is cheaper and easier to come by than bromine, especially since most box stores carry it. “Our store has always leaned more toward chlorine,” she says. “Every pool guy I know uses chlorine as their go-to product. As such, most pools and spas are on chlorine, but that doesn’t always mean it’s the right sanitizer to use.”

Bokor says to treat it like a prescription based upon how the water is used. “You have to examine and take in all the aspects of what is going on,” he says, from bather load to its environment: indoors, outdoors, exposed or covered. “All of those things come into play,” he says.

Arko agrees: “For [outdoor] swimming pools, chlorine is the preferred choice because it is effective, economical and is able to be stabilized by the use of CYA to prevent degradation from UV sunlight,” he says. “For spas [and indoor pools], bromine would be a better choice as it disinfects over broad pH ranges and has better efficacy at high temperatures.” “Both have a place in the industry,” Bokor says. “Sometimes one method is preferred over the other, but both are applicable.”


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