A simple answer would be, “Yes, chlorine can be used in hot tubs.”

However, just because the is the answer is “yes” does not mean chlorine is the ideal choice for you.

Chlorine is a powerful oxidizer and is the most popular choice of sanitization in the pool and hot tub industry. 

When chlorine is added to water it forms hypochlorous acid which invades bacterial cells and destroys the proteins which hold those cells together. As the functionality of the proteins deteriorates, the bacterial cells begin to die.

Under the right conditions, chlorine quickly kills contaminants such as E. coli, Pseudomonas, and Legionella, however the pH of the water and cyanuric acid (stabilizer) must be maintained appropriately for the chlorine to remain effective.

When chlorine reacts with contaminants, chemical compounds called chloramines are formed. Anything from sweat to body oil, hair, dead skin, detergents, or urine can cause this reaction and form chloramines in a hot tub. You’ll notice a strong and smelly odor when this reaction occurs, and this odor is commonly mistaken for a surplus of chlorine in the water. This odor is actually an indication that the hot tub is “dirty” and needs to be shocked in order for the reacted chlorine to once again become free and available to sanitize. Chloramines can be harsh on the skin, hair and eyes, and could trigger asthma or other respiratory allergies.

Chlorine is not the only choice of sanitizers available to pool and hot tub owners. Two other choices are Bromine and Biguanide.

When bromine is added to water it forms hypobromous acid which is a powerful disinfectant. Similar to chlorine, when bromine reacts with contaminants it forms chemical compounds called bromamines. Unlike chloramines however, bromamines remain effective at killing microbes. Bromine dissolves up to three times better than chlorine and is effective across a much larger window of pH than chlorine. A disadvantage of bromine however is that pound-for-pound it is more expensive than chlorine and it is highly reactive which means it degrades faster when exposed to sunlight and you’ll have to add it to your hot tub more frequently. For this reason, many hot tub owners choose to use a floating dispenser with slow dissolving bromine tablets.

Another alternative sanitizer which has been used in the pool and hot tub industry for many years is biguanide. Biguanide is a polymer which penetrates the cell wall of bacteria and kills them from within. The performance and efficacy of a biguanide-based system is not dependent on the pH of the water, and it does not degrade when exposed to sunlight or high water temperatures. Biguanide is very stable in pools and spas.

A disadvantage of biguanide is that it does not remove all contaminants from the water, so routine addition of a hydrogen peroxide shock must be done to oxidize any remaining contaminants. Additionally, biguanide is not compatible with a number of other hot tub products and supplemental sanitizers such as chlorine or bromine, salt chlorine/bromine generators, metal based ionizers, or ozone systems. Also, after prolonged use some microorganisms may become resistant to the biguanide sanitizer.

Hot tubs today are available with ionizers, ozone generators, and UV lights which can help to reduce the use of sanitizers but can not replace them entirely. Sanitizers (e.g., chlorine, bromine, or biguanide) are a must to keep hot tubs free of bacteria.

And don’t be fooled, a “saltwater” hot tub is still a chemical hot tub! In these systems, an electrolytic converter transforms salt (sodium chloride or sodium bromide) into hypochlorous or hypobromous acid. As a byproduct of this chemical reaction, the pH of the water will increase constantly so it becomes necessary to add regular doses of pH reducer to keep the water balanced.

Keep in mind, there are certain risks associated with improper use or handling of chemical sanitizers. Always be sure to follow your manufacturer’s instructions and the recommendations from your certified Water Care Experts at Rin Robyn Pools. Our friendly and knowledgeable staff is always here to provide guidance when choosing a sanitizer for your pool or hot tub, and our BioGuard ALEX professional water testing laboratory and Service Department can help you keep your hot tub sparkling clean and safe for you and your loved ones!