Bromine vs. Chlorine for Hot Tubs: Discover The Best Choice

Published on

April 16, 2023

Chlorine and bromine are chemicals often used for spa water sanitation. While chlorine is the most common sanitizing chemical, professionals often use bromine in hot tub maintenance. Chlorine kills bacteria faster, but bromine keeps them at bay for longer. The controversy about who would win the bromine and chlorine hot tub battle remains.

Bromine and chlorine come with benefits and drawbacks. But which one provides deeper cleaning? Is bromine more convenient than chlorine? Does chlorine need to be applied less often?

This article explores the advantages and disadvantages of using chlorine and bromine for hot tub sanitation.

You will also find details on the main aspects surrounding bromine and chlorine:

  • Composition
  • Cleaning process
  • Effectiveness
  • Application frequency
  • Frequency of use
  • Associated health risks

Bromine and Chlorine Hot Tub Use: Everything You Need To Know

Sanitizing agents, such as chlorine or bromine, keep the water inside hot tubs free of bacteria and other contaminants.

When hot tubs are used frequently and by many people, the water easily gets contaminated with bacteria, viruses, parasites, and enzymes. These contaminants come from sweat, wind-blown debris, and urine. 

Some hot tub contaminants can lead to potentially fatal health conditions, such as Legionnaires' disease.[1]

People prefer bromine or chlorine to other hot tub chemicals. After all, they display high effectiveness in warm water.

Hot tub owners should make an informed decision before applying any chemicals. Keeping a hot tub clean prevents illnesses but can also cause health issues if not used properly. 

Too much product can lead to red and itchy skin and eyes. Even the best sanitizer can affect the lungs if used in large quantities. The excessive use of sanitizing agents can also lead to the deterioration of the hot tub.

When using chlorine or bromine for water sanitation, it is essential to analyze these key factors:

  • If the cleaning agent is effective in killing bacteria and contaminants.
  • How frequently you need to reapply the product.
  • The health concerns associated with the use of the product.
  • What the costs are in regard to regular use
  • How easy it is to apply the product.
  • How the product works (to avoid hot tub damage).

We strongly recommend you don't mix chlorine and bromine under any circumstances, regardless of their state or concentration. This can lead to a dangerous chemical reaction that can risk your health.

Bromine and Chlorine Hot Tub Use: Everything You Need To Know

Is Chlorine Best for Hot Tubs? - A Reliable Simplistic Inquiry

Chlorine is a chemical element with sanitizing properties. It is used to sanitize industrial waste and sewage, as a bleaching agent for paper production, or as a cleaning product in the form of bleach.[2]

The spa industry commonly utilizes chlorine as a hot tub sanitizer agent for the water. It rapidly eliminates bacteria and contaminants compared to other hot tub chemicals. but this doesn't mean it's the best solution.

1. How Does Chlorine Work?

Chlorine sanitizes water in a chemical reaction called oxidation. This chemical reaction results in the death of water contaminants that can cause disease.

The mechanism behind how chlorine sanitizes water is not fully understood. Here is what we know so far:[3]

  1. Chlorine interacts with the membrane of the contaminant's cell, affecting its chemical bonds.
  2. The crucial constituents of the cell migrate outside the cell environment.
  3. The cellular membrane's vital functions disappear.
  4. Chlorine destroys the internal cellular function of the contaminant.

As a result, the contaminated water in your hot tub turns into fresh water.

2. What Are the Types of Chlorine for Hot Tub Use?

The most effective type of chlorine for hut tubs is sodium dichlor[4], found in the form of granules. Salt chlorine is also recommended for hot tub use.

Chlorine also comes in tablet form. Chlorine tablets are usually made of trichlor. Trichlor is recommended for sanitizing swimming pools but not hot tubs. Besides attacking contaminants, pool chemicals such as trichlor are highly acidic. As a result, they deteriorate the hot tub coating.

Calcium hypochlorite should also be avoided.

3. How Effective Is Chlorine for Hot Tub Water Sanitation?

Chlorine is highly effective in keeping hot tub water clean. It eliminates contaminants relatively fast but dissipates quickly. This means you have to reapply it more frequently. 

This table illustrates how long it takes for chlorine to kill hot tub pathogens.[5]

Pathogen Bromine Concentration Water pH Bromine Action Time
E. coli 0157:H7 1 ppm 7.5 < one-minute
Hepatitis A 1 ppm 7.5 16 minutes
Giardia 1 ppm 7.5 45 minutes
Cryptosporidium 1 ppm 7.5 10.6 days

4. How Much Chlorine Should I Use?

The effectiveness of chlorine-based products for hot tubs depends on chlorine levels and water pH levels.

The recommended amount of free chlorine concentration for hot tubs is at least 3 ppm. This is the equivalent of three milligrams of free chlorine for one litter of water. Chlorine levels should be combined with a water pH between 7.2 and 7.8.[6]

The amount of chlorine used to sanitize water is measured in parts per million(ppm). Your hot tub's volume is essential when verifying if you have reached the recommended level of 3 ppm.

You can measure the chlorine levels and pH of your hot tub water by using a DPD test kit or a test strip. Test strips are not as accurate as DPD tests but are a reliable alternative. 

5. How Often Should I Apply Chlorine?

We recommend you add chlorine to your hot tub at least once every week. 

Depending on the type of product you choose, you can reapply it after each use. If you skip the weekly application, it’s best to use the hot tub only after a sanitizing session.

How Often Should I Apply Chlorine?

6. Does the Use of Chlorine Affect My Health?

If used under proper conditions, chlorine does not cause severe health issues. But, people with sensitive skin or chlorine sensitivities should avoid using chlorine-based products. 

Here are the most common health issues caused by excessive chlorine hot tub use:

  • Respiratory problems
  • Skin irritation
  • Eye irritation
  • Nausea 
  • Vomiting
  • Itchy skin
  • Itchy eyes

7. Pros of Using Chlorine for Hot Tub Water

Here is a list of advantages chlorine presents in comparison to bromine or other hot tub chemicals:

  • Chlorine is cheaper than bromine.
  • It kills most pathogens quickly.
  • It leaves the hot tub water crystal clear.
  • Chlorine is not easily destroyed by UV light, which makes it perfect for an outdoor hot tub.

8. Cons of Using Chlorine for Hot Tub Water

Here are the disadvantages of using chlorine for hot tub sanitation:

  • Chlorine dissipates and leaves behind a waste product called "chloramines" which can be toxic.
  • Chlorine products that contain cyanuric acid take longer than free chlorine to kill pathogens.
  • It leaves behind a strong scent.

Is Bromine Best for Hot Tubs? - A Valid Expert Analysis

Bromine is a hot tub sanitizer found in nature. This brown-redish element has a liquid form at room temperature and dissolves in water.[7]

Ideal for people allergic to chlorine, bromine doesn’t irritate the eyes or the skin. As a result, people with sensitive skin prefer to use bromine for water sanitation, rather than chlorine.

1. How Does Bromine Work?

Bromine ionizes contaminants found in hot tubs. This leads to their destruction by tearing apart their chemical bonds. 

Bromine breaks bacteria and other pathogens down to the point they can no longer survive.

2. What Are the Types of Bromine for Hot Tub Use?

There are various types of bromine sanitizing products:

  • Bromine granules
  • Bromine tablets
  • Bromine sticks
  • Bromine salts

The best way to use bromine is by placing it into a diffuser, which provides proper dissolution.

We recommend you use bromine granules instead of bromine tablets, as they provide even water sanitation.

3. How Effective Is Bromine for Hot Tub Sanitation?

Bromine dissolves in water slowlier than chlorine. As a result, its sanitation effect doesn't happen as fast as with chlorine products.

Its effectiveness is similar to the one of chlorine. This makes bromine a great alternative for people who want to avoid chlorine-based chemicals.

This table illustrates the effectiveness of bromine use on various pathogens.[8]

Pathogen Bromine Concentration Water pH Bromine Action Time
E. coli 4 mg/L 7.55 5 – 30 minutes
Cryptosporidium parvum 5 mg/L 7.5 240 minutes (3 hours)
Pseudomonas aeruginosa 0.2 – 1.5 mg/L 7.5 0.5 – 3 minutes

4. How Much Bromine Should I Use?

You can ensure proper sanitizing levels if you keep bromine levels between 3 and 5 ppm. 

Levels below 3 ppm lead to improper sanitation, while levels above 5 ppm put the users’ health at risk.

5. How Often Should I Apply Bromine?

The frequency of applying bromine to hot tubs highly depends on your bathing habits or on how often people use the hot tub, in case you are a professional spa owner. 

We recommend checking the bromine concentration every three days. If you notice any variations from the recommended levels, add bromine according to the manufacturer’s instructions.

6. Effects on Health

Bromine is not as harsh on the skin as chlorine is but there is a debate on whether it is cancerogenic or not. 

While the International Agency for Research on Cancer does not list bromine as cancerogenic[9], some scientists suggest it can cause cancer. So far, there is no evidence that the use of bromine in the spa industry leads to cancer in humans.

More bromine does not mean fewer health issues. Both chlorine and bromine can lead to severe health conditions if not used properly.

7. Pros of Using Bromine for Hot Tub Water

Here are the advantages of hot tub bromine use:

  • Bromine does not dry the skin as much as chlorine.
  • It helps with maintaining water balance because it has a low pH. This raises the total alkalinity of the water.
  • Bromine‘s sanitizing effects last longer, which leads to a less frequent application.
  • Bromine is more effective in destroying certain pathogens at higher pH levels than other chemicals.

8. Cons of Using Bromine for Hot Tub Water

Here are the disadvantages of hot tub bromine use:

  • Bromine is harder to wash off the skin than chlorine.
  • It leaves the water in the hot tub cloudy.
  • Bromine requires more time to kill contaminants.

Bromine vs Chlorine Hot Tub Results: Reliable Differences and Similarities

While bromine and chlorine belong to the same family of chemicals, their use for hot tub sanitation differs to some extent. Both are effective in killing bacteria, viruses, enzymes, parasites, and other pathogens but take different times to do so.

Here are four similarities between chlorine and bromine:

  1. They are both halogens.
  2. They are suited for spas, as well as for swimming pools.
  3. They have almost the same effectiveness in killing hot tub pathogens. 
  4. Both chlorine and bromine can lead to similar health issues when used in excess.

This table illustrates the main differences between chlorine and bromine.

Key Factors Chlorine Bromine
Amount needed 3 ppm (optimal) 3 – 5 ppm
Action time Fast Slow
Water clarity Crystal clear Blurry
Effectiveness Superior Superior
Reactivity Is not affected by UV exposure Easily destroyed by UV rays
Type of pathogen destruction Oxidation Ionisation
Use frequency More frequent Less frequent
Price Affordable More expensive
Effect Doesn’t last long Lasts longer
Unpleasant odor Yes No
Suited for allergic people No Yes

A Risk-free Perspective on Hot Tub Chemicals

Chlorine and bromine are highly effective in the spa sanitation sector. But regular exposure to these chemicals can lead to various health conditions over time.[10][11]

Here is a list of health issues that can result from frequent exposure to chlorine or bromine:

  • Corneal epithelial erosions or dysfunction
  • “Swimmer's Ear”
  • Dry, itching, fragile skin
  • Eczema
  • Anosmia
  • Dyspnea
  • Muscular fatigue

If you are a residential hot tub owner, you still have to sanitize your it regularly.

The good news is that you can use less bromine and chlorine and reduce exposure to them. The use of O-Care products reduces the amount of chlorine and bromine required for sanitation by up to 78%.

A Risk-free Perspective on Hot Tub Chemicals


Bromine and chlorine are the most frequently used hot tub chemicals. Deciding whether to use chlorine or bromine depends on the hot tub owner’s needs.

We recommend chlorine for people who need to sanitize their hot tub water fast and want their water crystal clear. Chlorine is also suited for outdoor hot tub use because it is more stable under ultraviolet light than bromine.

Bromine is a great alternative for people allergic to chlorine or sensitive skin. If the scent of chlorine bothers you, bromine is a better choice. Bromine requires fewer applications, which makes it perfect for busy people. To make the hot tub experience more pleasant regardless of the sanitizer you use, consider using O-Care for simple, soft, and safe hot tub water maintenance.