How many bromine tablets do you need in your hot tub?  - Sutro, Inc

How many bromine tablets do you need in your hot tub? 

Bromine is a popular alternative to chlorine, especially in hot tubs. It has many advantages; however, preparing and adding it in the correct quantity is crucial. 

Read this guide to understand how many bromine tablets you need to add to a hot tub. 

The difference between chlorine and bromine 

Chlorine is the more common water sanitizer because of its easy availability and low price. However, in the case of hot tubs, bromine is the better option because of its resistance to high temperatures

Chlorine is an effective sanitizer, but it is also quite unstable. While it is prone to quick reduction under direct sunlight (UV rays), it also becomes ineffective under high temperatures, like in a hot tub. 

Here are a few advantages of using bromine over chlorine in a hot tub:

  • Bromine has a lower pH and is less prone to pH fluctuations making it easier to maintain the water balance.
  • It is more stable than chlorine under high temperatures and sunlight.
  • Bromine is gentler on the skin compared to chlorine.
  • It has a mild smell that does not irritate.

Conversely, bromine is also more expensive, needs twice the amount, and works slower than chlorine. 

Pro Tip: If you smell an overpowering odor from your bromine hot tub, it is time to shock it. 

Can you switch between Bromine and Chlorine?

You can switch between the two, but the process can be tedious. You cannot simply stop using one and add another to the hot tub. Remember, never mix chlorine and bromine because the chemical reaction will be hazardous and cloud the water.  

The best and most reliable method to switch between chlorine and bromine is to drain and rinse the hot tub. Refill it with water and add the sanitizer of your choice. 

You'll also need to purge the plumbing with appropriate hot tub chemicals to avoid any chances of these two chemicals mixing. Never fill an existing chlorine dispenser with bromine or vice versa. When switching between the two, always use a fresh dispenser.

Why do you need to add bromine to your hot tub? 

Bromine is a water sanitizer used to kill any microorganisms like algae or fungi in the water. It is also an oxidizer that can be used in high quantities to shock the hot tub to destroy organic contaminants that have taken over the water.

Since chlorine is not very effective under direct sunlight and high temperatures, bromine is the only option as it has a slower depletion rate. Additionally, people who are allergic to chlorine or dislike its smell are bound to use bromine in their hot tubs.

When do you need bromine tablets for your hot tub? 

You need to add bromine to your hot tub in two situations - building a bromine bank and shocking the hot tub. However, a shock is often the first process.

When you drained, cleaned, and refilled your hot tub, add a hard dose of sodium bromide to create hypobromous acid. Doing this activates the bromide ions, which will start the sanitization and oxidation process of the water. 

The other reason is to build a ‘bromide bank’ that refers to maintaining the optimal bromide levels in hot tub water. This task is usually automated using bromine dispensers (also called floaters or brominators) by adjusting them to the proper settings. Additionally, you can test the water every few days to add bromine for appropriate adjustments. 

You can choose between granular bromine and tablets. 

Granular bromine is the faster method of raising the bromine levels in your hot tub, whereas tablets are suitable for maintenance and a prolonged approach. 

Pro Tip: We have found that crushing tablets and turning them into powder allows the bromine to work faster. 

How many bromine tablets do I need to add to my hot tub? 

It depends on the current bromine levels in your hot tub water. The best method to know how many is to do a test. You can use pool hot tub test kits to measure bromine levels but be aware that not all kits test for it.

Use a smart pool water monitor system

Another alternative is to use an automated digital system like our Sutro hot tub Monitor. It tests your hot tub water three times daily for bromine levels and sends the data and recommendations to an app on your mobile phone. 

What are the ideal bromine levels for a hot tub?

The optimal bromine levels for a hot tub are between 3-5 ppm (1-3 ppm if your hot tub has an Ozonator). 

Factors determining how many bromine tablets to use  

The number of tablets will depend upon the volume of your hot tub, the current levels, and brominator/feeder settings.

Maintaining an active bromine residual of two ppm takes one tablet per 100 gallons of water

If the bromine levels are below two ppm or less, use granular bromine instead of tablets. You can also do this by crushing the pills to a powdered form. 

It is safe to enter the hot tub thirty minutes after adding the tablets to the hot tub. Although, doing a quick test is the best way to decide. 

How many bromine tablets do you need for an inflatable hot tub? 

Inflatable hot tubs also need bromine, and maintaining water balance is the same as a fixed hot tub. The number of bromine tablets will depend upon the current bromine levels and the hot tub volume. That is one one-inch tablet per 100 gallons of water to maintain a bromine level of 2 ppm. 

How often do I need to add bromine tablets?

The answer depends upon the current bromine levels of your hot tub water. Since bromine is a sanitizer, it is best to test the levels daily or once every couple of days. Add tablets in appropriate quantities to keep the bromine levels between 3-5 ppm. 

What to do if you put too much bromine in a hot tub?

Adding too much bromine to your hot tub can result in water imbalance (too low total alkalinity) and skin issues for anybody who uses it. Here’s what you can do to counter it:

  • Do not use the hot tub to let the bromine dissipate naturally. That can take a few days.
  • Expose the water to direct sunlight for some time.
  • Partially drain the hot tub and refill it with fresh water.
  • Use a neutralizer chemical.
  • If the water is unbalanced, drain and fill the hot tub with fresh water.


Bromine’s resistance to high temperatures and sunlight makes it an effective alternative to chlorine for hot tubs. The ideal bromine levels in a hot tub fall between 3-5 ppm, and the number of tablets you’ll need depends upon the volume of the hot tub and current levels.

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