Hot Tub Chemicals and Sanitizers

Hot Tub Chemicals and Sanitizers

All hot tubs require chemicals as sanitizers in order to keep the water clean and clear. Sanitizers are chemicals that you add to your spa’s water periodically to kill bacteria and odor. ThermoSpas offers several different methods to chemically sanitize your spa’s water, but the choice is yours, based on the one that works best for your lifestyle and budget.

ThermoClear supplies
Thermo Clear supplies

Thermo Clear
Hot tub chemicals may be irritating to sensitive skin, so Thermo Spas developed Thermo Clear; a two-step, mineral-based system that is extremely easy to use and is compatible with all hot tub brands. It’s so simple and effective that each new Thermo Spas hot tub comes with a Thermo Clear starter kit and instructions, unless you prefer one of the methods below. With Thermo Clear, when your spa is not in use, there is no maintenance required for up to four months! Just place the Thermo Clear cartridge in the spa’s filter. Then, 20 minutes before each use, simply add Spa Activator to the spa’s water. It is also recommended to add Chlorinating Granules to your spa once a week, or after heavy usage.

Test the water weekly with simple test strips.

Thermo Clear Advantages:

  • Works up to 15x faster than chlorine
  • Reduces scum lines and foam
  • Produces clear water, with no odor
  • Helps eliminate eye and skin irritations
  • Won’t bleach out swimming apparel
  • Enhances the efficiency of an Ozonator


  • Not compatible with bromine

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Chlorine is considered to be the most effective of all hot tub chemicals that you can use to sanitize your hot tub. However, it must be added regularly to be effective because it is the Free Chlorine that acts as a sanitizer, as opposed to Combined Chlorine, which has already combined with other substances and is no longer capable of sanitizing. To use Chlorine as a system by itself, simply add Chlorinating Granules to your hot tub every other day to keep your water clean. It is important to keep adding the granules because Free Chlorine does not store in the water. For heavy usage, we also recommend shocking the water with Spa Activator.

Test the Chlorine regularly to maintain the proper levels.

Chlorine Advantages:

  • Less chance of staining your shell
  • Does not affect pH balance
  • Highly soluble and fast acting
  • May be used with Thermo Clear (above)


  • The scent can be offensive
  • May cause skin irritations
  • Must be used regularly

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Two-Part Bromine
Bromine is a good alternative for those who do not wish to use Chlorine. Two-Part Bromine consists of two ingredients: Bromide Liquid Salts, which is the primary sanitizer, and Spa Activator, which acts to “shock” the water and activate the sanitizer. The Bromide Salts should be added once a week to maintain an available supply of sanitizer. Then, Spa Activator must be added each time you leave the hot tub to trigger the sanitizer. This system uses enough sanitizer to kill the existing bacteria, while the remaining Bromine sanitizer is saved in the water for future use.

Test the Bromine weekly to maintain proper balance.

Two-Part Bromine Advantages:

  • No odor or eye burn if used properly
  • Does not affect pH balance
  • Most effective Bromine system available


  • Requires the use of two chemicals

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Bromine Tablets
Bromine Dispenser
Spa Activator

Bromine Tablets
Bromine tablets are used with our Bromine Float Dispenser to create a system that is simple to use and only costs a few pennies a day. Simply keep two Bromine Tablets in the Float Dispenser to provide continuous disinfecting of your hot tub. It is also recommended that you shock the water with Spa Activator once a week, or after heavy use.

Test the Bromine regularly to maintain proper levels.

Bromine Tablet Advantages:

  • Easy to use
  • Convenient tablet form


  • A slight odor may exist
  • Tablets affect pH balance
  • May bleach the hot tub shell
  • Avoid if you are allergic to Chlorine

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Total Dissolved Solids (TDS)
It is important to note that the water in every hot tub reaches a saturation point where the chemicals can no longer effectively sanitize the water. This saturation happens when the Total Dissolved Solids level exceeds the point where new chemicals can ‘fit’ in between the molecules of water. It is like pouring a whole container of sugar into a cup of coffee. Eventually, there is no more room for the sugar to dissolve, so it just settles into the bottom of the cup. Therefore, test the Total Dissolved Solids monthly to ensure the level does not prohibit the hot tub chemicals from being effective.

Regardless of which chemical sanitizing system you choose , you should consider adding a Therm Ozone Ozonator to your spa to reduce the amount of chemicals required.

Also, please remember that proper water chemistry is essential to user safety and the life of the spa components. Thermo Clear and Chlorine may be used interchangeably, but switching to other chemicals requires draining and cleaning the spa with Jet Line Cleaner.

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