The Main Hot Tub Start-up Chemicals and How to Use Them

Published on

July 6, 2024

Hot tubs have become highly popular as more people seek ways to relax, unwind, and improve their overall health and wellness. Studies show that soaking in hot water can help relieve stress, soothe sore muscles, and enhance sleep quality.

Hot tub ownership has risen, with about 7.3 million owners in the U.S. The growing popularity of hot tubs highlights the importance of understanding hot tub water chemistry and the proper use of hot tub start-up chemicals. This ensures that the water in your hot tub is clean, clear, and safe. Water safety is essential for both a professional and a residential hot tub owner.

This blog post covers everything from sanitizers to pH adjusters, shock treatments to clarifiers. You will learn what they are, how to properly dose them, and safety considerations.

What are Hot Tub Start-Up Chemicals?

hot tub start up chemicals

Hot tub start-up chemicals are used to properly balance and sanitize the water in a new or recently drained hot tub. They help ensure a safe and comfortable soaking experience by controlling pH levels, total alkalinity, sanitizer levels, and other factors that affect water quality.

Types of Hot Tub Start-up Chemicals

No matter what type of hot tub you own, the proper chemical balance is essential for maintaining spa water clean and safe. Start-up spa chemicals come in various options. Add hot tub chemicals in a freshly filled hot tub for the first time or after draining and refilling the water.

This table illustrates the most common chemicals used for hot tubs:

hot tub chemicals purpose

1. Sanitizers

Sanitizers are essential for maintaining a contaminant-free hot tub or environment. The most commonly used sanitizers are:

You can test hot tub water using test strips or a digital hot tub tester to check chlorine levels and ensure that waste products called chloramines are not present in the water.

Chlorine is a strong oxidizer that kills bacteria quickly but can be harsher on the skin. Bromine is gentler but doesn't kill bacteria as fast as chlorine.

Bromine granules have an added advantage because they function better in hot temperatures than chlorine tablets. Use chlorine or bromine and test strips regularly to keep your spa water clean and maintain a safe hot tub environment.

It is essential to ensure the chemicals completely dissolve in the hot tub's water.

2. pH Adjusters

The pH level of a hot tub's water should remain between 7.2 and 7.8 for optimal efficiency and cleanliness. If it is too low, it can cause skin irritation and damage to equipment. You can use specialized pH increasers and decreasers to raise or lower the spa water's pH level as needed.

The most popular pH increaser chemicals used in hot tubs are:

  • Sodium carbonate (also known as soda ash).
  • Sodium bicarbonate (baking soda).
  • Calcium chloride.

The pH decreaser chemicals usually used in hot tubs are muriatic acid and sodium bisulfate.

3. Alkalinity Adjusters

Alkalinity adjusters help keep your hot tub's water balanced by regulating its total alkalinity levels. Low alkalinity can cause the pH to become too acidic. In contrast, high alkalinity raises the pH and makes it challenging to balance. Alkalinity adjusters restore the water's balance between 80-120 ppm.

The most common alkalinity adjusters used in hot tubs are:

  • Sodium bicarbonate: It is the most widely used alkalinity adjuster as it is cost-effective and easy to handle.
  • Potassium bicarbonate: It is a more expensive option but has a long-term effect on the water's balance and is eco-friendly.
  • Trisodium phosphate: It is more expensive than sodium bicarbonate but can provide quick results. It also adjusts the alkalinity levels of even the most challenging hot tubs.

4. Shock Treatments

Use shock treatments periodically to break down organic matter accumulated in the hot tub's water. There are two types of shock treatments: chlorine and non-chlorine. Use chlorine shock according to the manufacturer's directions. You can use non-chlorine shock more frequently but it may be less effective in breaking down organic matter.

5. Clarifiers

Clarifiers help keep your hot tub's water crystal clear and free of particles. Hot tub clarifiers work by trapping tiny particles that would otherwise stay suspended in the water and making them large enough to be filtered out.

6. Metal Removers

Metal remover products prevent the build-up of minerals such as calcium and iron in your hot tub's water. Over time, these minerals can cause scaling on the tub's surface and clog hot tub filters.

Adding a mineral remover to your hot tub during start-up will help to ensure that your water stays clean and crystal clear.

7. Calcium Hardness Balancers

Starting up a hot tub requires balancing calcium hardness levels. Too much calcium in the water can lead to scale build-up on the walls, jets, and other hot tub surfaces. This can cause staining and even blockage of jets and filters.

If there is not enough calcium hardness in the hot tub water, it can cause corrosion of equipment and surfaces.

Calcium hardness balancers can maintain the proper calcium levels in the water. These products come in two forms: liquid solutions or granules that can be added directly to the hot tub.

They usually contain sodium carbonate, which helps raise the pH level and stabilize the calcium hardness levels. Once added, you should test your water to ensure it has reached the desired levels and adjust as needed.

Read more: 

Why Are Start-up Chemicals Essential for Hot Tubs?

Hot tubs require special care when it comes to adding chemicals. While the actual process is not complex, it is vital to ensure that you use the right chemicals in the proper proportions. Testing the water using a digital hot tub tester can come in handy. 

When first filling a hot tub, it is essential to use start-up chemicals. This ensures proper sanitization and oxidation.

Start-up chemicals also help prevent calcification and scaling and bacteria and algae growth. Adding the right amount of start-up chemicals can also help to avoid cloudy water in your hot tub, which can make it unpleasant to use.

Proper Use and Dosage of Hot Tub Start-Up Chemicals

start up chemicals use dosage

The first step in starting your hot tub is to ensure all the necessary chemicals are added. This includes:

  • Chlorine
  • pH adjusters
  • Scale inhibitors
  • Algaecides
  • Other sanitizers if needed

All these chemicals should be added using a floating chemical dispenser system. This helps to distribute the chemicals evenly throughout the water.

Recommendations for Specific Chemicals and Dosages

This table illustrates how to use the most common chemicals when starting your hot tub:

hot tub chemicals use

Maintenance and Ongoing Use of Hot Tub Chemicals

hot tub maintenance

To better understand hot tub maintenance, hot tub owners need to know:

  1. The factors that affect spa water balance.
  2. How often to test their water and why it’s important.
  3. The alternative methods of starting up their spa.

1. Factors That Affect the Balance of Hot Tub Water

Hot tub water must be balanced and maintained correctly to keep it safe and enjoyable. Several factors can affect the balance of hot tub chemistry, including bather load, temperature, and sun exposure.

  • Bather Load: High concentrations of bathers in a hot tub can cause an increase in the total dissolved solids (TDS) levels in the water. This can lead to cloudy or foamy water, skin irritation, and other health issues. To counteract this issue, it's essential to regularly monitor TDS levels when there is a high bather load. Regular testing will also help prevent scale build-up due to high calcium hardness levels.
  • Temperature: Hot tub water temperature plays a vital role in the hot tub water balance. According to the CDC, too much heat can cause bacteria to grow faster, resulting in cloudy or foamy water and nasty hot tub smells.
  • Sun Exposure: Sun exposure can also affect the well-balancedness of your hot tub water. UV rays from the sun can cause chlorine levels to drop, leading to an increase in bacteria and algae growth. To counteract this issue, you should use an algaecide every few weeks and ensure your hot tub cover is secure when not in use.

2. Recommended Frequency of Water Testing and Chemical Adjustments

Owning a hot tub is an investment. One of the best ways to ensure your investment stays in good condition is by regularly testing and adjusting the water chemistry.

It's important to test the chemical balance of your hot tub at least once a week, but more often if you use it frequently or have more than one person using it.

There are a few different ways to test the water in your hot tub, but the most common and accurate way is to use a digital water tester. These testers give you an instant readout of:

  • pH
  • Alkalinity
  • Calcium hardness levels

You can also purchase test strips, which will provide less accurate results.

Once you have tested and analyzed the levels, you may need to adjust the chemicals in your hot tub accordingly. This needs to be done every time there is an imbalance in the results.

Importance of Water Testing Before and After Adding Hot Tub Start-Up Chemicals

Make sure to test your hot tub's water before adding any start-up chemicals. This helps you determine what specific adjustments need to be made for the hot tub to be safe.

Once all the chemicals have been added, it is essential to test the water again to ensure all levels are within acceptable limits.

Alternative Methods for Maintaining Water Quality in a Hot Tub

The most common alternative methods for hot tub maintenance are ozonators and mineral products.

Ozonators introduce ozone into the hot tub water. This helps control contaminants like microorganisms. As an alternative to chemicals, they keep the water clean without requiring frequent chemical adjustments.

Mineral products use zinc and copper ions to reduce bacteria levels in the water and require less chemical usage. They can be used alone or in combination with a traditional system for added protection against bacteria and algae.

The O-Care Effect

O-Care is a hot tub mineral product that reduces the amount of sanitizer you need by up to 78%. It protects hot tubs from sediment build-up and lets you enjoy your bath without the smell of chemicals all around.

There is no unpleasant smell on your skin after you get out of the hot tub. O-Care is not a biocide, making it safe for anyone, even children. 

Use our store locator to find the nearest O-Care store. Discover the transformative benefits of O-Care for your hot tub and adopt a more natural approach to water care. 

Safety Considerations

hot tub chemicals safety

Safety Considerations

Precautions to Take When Handling and Using Hot Tub Chemicals

Here is a list of the precautions you need to take when handling and using hot tub chemicals:

  • Read and follow the manufacturer's instructions for each chemical carefully before use.
  • Avoid inhaling chemical fumes or vapors.
  • Only mix chemicals together if specifically directed to do so.
  • Use chemicals in a well-ventilated area, away from sparks and open flames.
  • Rinse hands thoroughly with water after handling chemicals.
  • Learn the capacity of your hot tub to adjust the quantity according to how many water gallons your hot tub holds.

Compatible and Incompatible Hot Tub Chemicals

Keep this in mind before combining different types of spa chemicals:

  • Chlorine and bromine sanitizers should not be mixed or other chemicals, as this can cause a dangerous reaction.
  • Acidic chemicals such as pH decreasers should not be combined with alkaline chemicals such as pH or alkalinity increasers. This can cause a dangerous reaction.
  • Oxidizing and non-oxidizing shocks should not be mixed with other chemicals. This can cause a decrease in effectiveness or dangerous hazardous reactions.
  • Avoid mixing different brands or chemicals, as compatibility may vary between them.

How to Store and Handle Hot Tub Chemicals Safely

Here are some tips on how to store and handle hot tub chemicals safely:

  • Wear protective gloves and eye protection when handling chemicals.
  • Store chemicals in a cool, dry place, away from direct sunlight and heat sources.
  • Keep chemicals out of reach of children and pets.
  • Never reuse containers for storing chemicals or for any other purpose.
  • Dispose of empty chemical containers and unused chemicals by local regulations.

Frequently Asked Questions

How do I properly adjust pH levels in hot tub water?

Test the water's pH level using a test strip or digital test kit. If the pH level is too low (below 7.2), add a pH increaser such as sodium carbonate or hydroxide. If the pH level is too high (above 7.8), add a pH decreaser such as sodium bisulfate or muriatic acid. Wait at least 15 minutes and retest the pH level. Repeat steps two and three as necessary until the desired 7.2-7.8 level is achieved.

Should I shock my hot tub at start-up?

Yes, it is generally recommended to shock your hot tub at start-up to ensure that the water is safe and clean for use. When a hot tub is not used for a period of time, bacteria and other contaminants can build up in the water.

When should I use shock treatments in a hot tub?

It would help if you used shock treatments after heavy or high bather load. This removes accumulated organic matter and restores water clarity. Shock treatments are also essential when the water appears cloudy or has an unpleasant odor. Suppose the total alkalinity or pH levels exceed the recommended range of 7.2-7.8 and 80-120 ppm. In that case, respectively, shock treatments can be helpful.


Using the right start-up chemicals is important for maintaining clean, safe hot tub water. Proper chemical balance prevents harmful bacteria and contaminants, ensuring a healthy soaking experience. Always consult a professional for guidance on the correct products and dosages.

For those seeking a natural maintenance alternative, O-Care reduces the need for harsh chemicals like chlorine and bromine, making your hot tub experience gentler and more enjoyable. Enjoy a crystal-clear, odor-free soak with O-Care, an eco-friendly solution for your hot tub maintenance needs.

Contact us for more information on how to improve your soaking experience. Our virtual water assistant can help you troubleshoot hot tub water issues and you can also do this using the O-Care app. Use our convenient store locator to visit the nearest store where you can buy O-Care now for an enhanced hot tub wellness experience!