What Chemicals Do I Need for a Hot Tub?

One of the most important aspects of maintaining a hot tub is keeping it chemically balanced. Without the right balance, your hot tub will become a breeding ground for bacteria and other harmful microorganisms.

However, with so many different chemicals available, it can be difficult to know which ones you need and how to use them effectively.

In this article, we’ll cover all the essentials of hot tub chemistry — the right chemicals for hot tubs, how to use them, and other maintenance strategies.

Key Takeaways

Understanding hot tub chemistry is key to maintaining a clean and safe hot tub.
The essential hot tub chemicals include a sanitiser, shock treatment, alkalinity increaser, pH increaser, pH decreaser, and calcium hardness increaser.
Regular maintenance and use of the right chemicals can keep your hot tub clean and free from harmful bacteria.

What is the Chemical Balance in a Hot Tub?

Chemical balance refers to maintaining the correct pH, alkalinity, and sanitiser levels in the hot tub water. It ensures your hot tub is clean, safe and comfortable while preventing damages or bacterial growth in the water.

You need to check the level of chemicals in your hot tub using a test kit or strips, as it’s important for your health and your spa's longevity.

For example, too much or too little of any chemical can cause the water to become unbalanced, leading to problems such as skin irritation, equipment damage, and an unpleasant odour.

The rule of thumb is to keep your pH level between 7.2 and 7.8 and your alkalinity level between 80 and 120 ppm (parts per million). Also, the level you maintain depends on the type of sanitiser used.

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Hot Tub Chemistry

The three main components of hot tub chemistry are:

1. Total Alkalinity (TA) :

This measures the water’s ability to resist pH changes. It acts as a buffer to prevent sudden shifts in pH levels. For instance, if alkalinity is too low, the pH levels can fluctuate, leading to corrosion. If it’s too high, the water can become cloudy and cause scaling. The ideal range for a hot tub is 80–120 ppm.

2. pH Levels:

This indicates how acidic or basic the water is. Low pH level (acidic) can cause skin irritation, damage equipment, and corrode metal parts. On the flip side, a high pH (alkaline) can lead to scale buildup and cloudy water. The recommended pH for hot tubs is 7.2–7.8.

3. Total Hardness (TH):

This refers to the amount of dissolved calcium and magnesium in the water. Low hardness leads to foamy water and equipment corrosion, while high hardness can cause scale build up in the water. The ideal hardness range is 150–250 ppm.

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Why Does Your Hot Tub Need Chemicals?

Your hot tub needs chemicals to maintain the correct balance of pH, alkalinity, and sanitiser levels.

Without the proper levels of these chemicals, your hot tub water can become cloudy, foamy, or even green. This can be a breeding ground for bacteria and other harmful organisms that can cause skin irritation, eye infections, and other health problems.

Other benefits of using hot tub chemicals are:

Prevents Scale and Corrosion: Proper chemical balance prevents scale buildup on your hot tub’s surfaces and components. It also protects the metal parts from corrosion.
Improving Water Clarity: Balanced water chemistry keeps your tub water crystal-clear and prevents foam buildup.
Extend Equipment Lifespan: Maintaining the proper chemical levels reduces wear and tear on your hot tub’s pump, heater, and other hardware components.
Eliminates Odors: Regular use of sanitisers prevents unpleasant smells caused by bacteria, algae, or organic contaminants.
Provides a Safe and Enjoyable Experience: Properly treated water keeps your hot tub inviting, hygienic, and comfortable for you and your guests.

To maintain crystal-clear water after balancing your spa, learn how to shock a hot tub and keep it safe from harmful bacteria.

Types of Hot Tub Chemicals

Here are the essential hot tub chemicals you need to keep your hot tub well-maintained:

Hot Tub Sanitisers

Sanitisers kill bacteria and other harmful microorganisms in your hot tub water. Typically, there are two main sanitisers used for hot tubs: chlorine and bromine.

Chlorine is the most widely used sanitizer for hot tubs due to its strong ability to kill bacteria, viruses, and other harmful contaminants. It helps keep the water clean and safe while preventing the buildup of algae and biofilm.

However, chlorine has a strong smell and can sometimes cause skin or eye irritation, especially if the levels are too high.

How it works:

When added to hot tub water, chlorine reacts with water to form hypochlorous acid (HOCl) and hypochlorite ions (OCl⁻), which break down bacteria and organic matter. The effectiveness of chlorine depends on the water’s pH level, which should be maintained between 7.2 and 7.8 for optimal sanitization.

Bromine is a good alternative if you prefer sitting at a higher temperature. It can stay at a stable temperature even when the heat is up. It is less harsh than chlorine and remains effective at higher temperatures, making it ideal for hot tubs. Although bromine takes longer to dissolve, it provides longer-lasting sanitation and produces fewer odours.

Since water temperature affects chemical effectiveness, find out how long it takes a hot tub to heat up before adding your treatments.

How it works:

When added to hot tub water, bromine dissolves and forms hypobromous acid (HOBr), which kills bacteria and organic contaminants. Unlike chlorine, bromine remains active even after combining with contaminants, meaning it continues to sanitize the water longer before needing replacement.

Tip: Don’t combine chlorine and bromine, as it can lead to a dangerous and corrosive reaction. If you want to switch chemicals, drain and wash your tub thoroughly before adding the new chemical to fresh water.

Hot Tub Shock

Shocking your hot tub means adding a large dose of sanitisers (chlorine or non-chlorine) to kill bacteria and other microorganisms in the water. It can also reactivate sanitisers like Bromine or Chlorine in the hot tub.

Tip: We recommend shocking your hot tub once a week after you change the water or more if you use it frequently.

pH Adjusting Chemicals

If the pH level is too low, the water becomes acidic and causes skin irritation. High pH level turns the water too alkaline, which causes scaling, irritation or cloudy water. At most, keep the pH level between 7.2 and 7.8.

pH adjusting chemicals help to keep the pH level of your hot tub water balanced.

How to Adjust pH Levels in Your Hot Tub

To increase the pH level in your hot tub, use a pH increaser like soda ash (sodium carbonate) or baking soda (sodium bicarbonate). If you intend to decrease it to normal levels, a pH decreaser like sodium bisulphate and muriatic acid will do the trick.

If pH is too low (below 7.2)

Use a pH Increaser (Sodium Carbonate or Soda Ash) to raise the pH.
Add the chemical gradually and let the jets circulate the water for even distribution.
Retest after 15-30 minutes and adjust if necessary.

If pH is too high (above 7.8)

Use a pH Decreaser (Sodium Bisulfate or Muriatic Acid) to lower the pH.
Add the chemical slowly while the water is circulating.
Retest and make small adjustments as needed

Calcium Hardness Increaser

A calcium hardness increaser helps raise the calcium levels in your hot tub water. If the calcium levels are below 100 - 150 ppm (i.e., they become soft), it can erode the tile grouting or corrode the metal parts. Use a calcium hardness increaser like calcium chloride to raise the calcium levels.

Similarly, a high calcium hardness (above 250 ppm) isn’t safe because the water can get cloudy, and the particles clog your hot tub equipment. In this case, use a scale control product to prevent calcium from solidifying on your hot tub's shell and internal parts or change the water completely to a fresh one.

Hot Tub Line Flush Cleaner

Over time, your hot tub's plumbing can accumulate debris, oils, and other contaminants. A hot tub line flush cleaner helps remove these contaminants and keep your hot tub plumbing clean. Use one every three months or whenever you drain and refill your hot tub.

Optional Chemicals

In addition to the essential hot tub chemicals, there are other optional chemicals that you can use to keep your hot tub water clean and clear:

Water clarifier: This device helps clear cloudy water by binding tiny particles together so the filter can easily remove them.
Metal sequestrant: This helps to prevent metal stains, and the filter cleaner cleans your hot tub filter.
Filter cleaner: It removes oils, grease, and other debris from your hot tub filter to improve the filtration.
Deafoamer: This device eliminates excess foam caused by body oils, lotions, or soaps.
Water conditioner: This helps soften the water, make it feel smoother on the skin, and reduce chemical odours.
Hot tub enzymes: This helps to break down organic contaminants such as body oils, lotions, and sunscreens.
303 Aerospace Protectant: This UV protectant for hot tub covers prevents fading, cracking, and weather damage.

Tip: Follow the instructions on the chemical labels and test your hot tub water regularly to ensure that the chemical levels are balanced.

How to Add Chemicals to Your Hot Tub

Maintaining the chemical balance of your hot tub is essential to keep it clean and safe to use. Here's everything you need to know about adding chemicals to your hot tub.

What Order Do You Add Hot Tub Chemicals?

It is crucial to add hot tub chemicals correctly to ensure they work effectively. Follow this order when adding chemicals to your hot tub:

Sanitiser: Add the sanitiser first to kill any bacteria or germs in the water. Chlorine and bromine are the most commonly used sanitisers for hot tubs.
Shock: Shock your hot tub regularly to remove any organic matter the sanitiser may have missed. Do this at least once a week.
pH Increaser or Decreaser: Your hot tub's pH should be between 7.2 and 7.8. Use a pH increaser to raise it or a pH decreaser to lower it.
Alkalinity Increaser: Alkalinity helps stabilise a hot tub's pH level. The ideal alkalinity level is between 80 and 120 ppm.
Calcium Hardness Increaser: Calcium hardness helps prevent corrosion of hot tub equipment. A hot tub's ideal calcium hardness level is between 150 and 250 ppm.

Hot Tub Care

To keep your hot tub clean and safe to use, follow these tips:

Regularly test the water in your hot tub using a test strip or kit to ensure the chemical balance is correct.
Drain and refill your hot tub every three to four months to prevent the build-up of minerals and other contaminants.
Use a hot tub cover when not in use to prevent debris from getting into the water.
Clean your hot tub filter regularly to ensure it is working effectively.
If you have an inflatable hot tub, follow the manufacturer's chemical use and care instructions.

By following these tips, you can ensure that your hot tub stays clean, safe, and enjoyable.

Hot Tub Chemical Maintenance

Maintaining the chemical balance in your hot tub is crucial to keeping the water clean and safe. This section will discuss how often and how long you should add chemicals and how long they last.

How Often Should You Add Hot Tub Chemicals?

Add chemicals at least twice a week to maintain the chemical balance in your hot tub. Also, use test strips to check the chemical levels before adding chemicals to be sure you’re adding the right chemicals and not over-treating.

Tip: Add the chemicals to your spa with the pump running and the jets on. This will help distribute the chemicals evenly throughout the water.

How Long Do Hot Tub Chemicals Last?

The length of time that hot tub chemicals last depends on several factors, including the hot tub size, how often it is used, and the type of chemicals used.

Most spa chemicals last a few weeks, but you should check the chemical levels regularly to ensure they are still effective. If you notice that the chemical levels are low, add more chemicals to your hot tub.

When using the hot tub for the first time, wait at least 24 hours after adding the chemicals to your spa. This will allow the chemicals to sanitise the hot tub and ensure the water is safe.

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How to Use Hot Tub Chemicals Safely

Safety should always be a top priority when maintaining a hot tub. Chemicals like chlorine and bromine can be dangerous if not handled properly.

Here are some tips for using hot tub chemicals safely:

Always wear protective gloves and eyewear when handling chemicals.
Never mix different types of chemicals.
Add chemicals to the water slowly and carefully, following the instructions on the label.
Do not use your hot tub immediately after adding chemicals to the water. Wait 15-30 minutes for the chemicals to disperse evenly throughout the water.
If you accidentally spill chemicals on your skin, rinse the affected area with water immediately.

How to Store Your Hot Tub Chemicals

Proper storage of your hot tub chemicals is essential for safety and effectiveness. Here are some tips for storing your hot tub chemicals:

Always buy your chemicals from a reputable supplier.
Keep your chemicals in a cool, dry place away from direct sunlight.
Store your chemicals out of reach of children and pets.
Do not store your chemicals near any flammable materials.
Make sure your chemicals are properly labelled and marked.
Check your chemicals' expiration dates and dispose of expired products safely.
If you have a saltwater hot tub, store your salt in a dry location away from moisture.

Conclusion

Maintaining the chemical balance of your hot tub is crucial to keeping it clean, safe, and enjoyable. Regularly testing and adjusting the chemical levels will help prevent skin irritation, cloudy water, and unpleasant odours.

Always follow the manufacturer's instructions when adding chemicals to your hot tub. Wear protective gloves and goggles when handling chemicals, and never mix different types of chemicals.

To summarise, here are the key takeaways for what chemicals you need for your hot tub:

Chlorine or bromine are the primary sanitisers used to kill bacteria and other contaminants in water. For best (and safe) practices, maintain the chlorine or bromine level between 3 and 5 mg/l.
To prevent skin irritation and cloudy water, keep the pH levels between 7.2 and 7.8. To do this, use pH adjusters such as sodium carbonate or sodium bisulphate.
Alkalinity levels between 80 and 120mg/l help stabilise the pH levels and prevent corrosion. Use alkalinity adjusters such as sodium bicarbonate to keep the alkalinity levels within the recommended range.
Calcium levels between 100 and 250mg/l prevent corrosion and scale buildup. Use calcium hardness adjusters such as calcium chloride or calcium carbonate to keep the calcium levels within the recommended range.
Shock treatments help oxidise and remove organic contaminants such as sweat, oils, and lotions from the water. Use shock treatments, such as chlorine or non-chlorine shock, weekly or after heavy usage.

If you’d prefer personalised recommendations, contact any of our experts for a consultation.

Common Questions About Hot Tub Chemicals

Here are some common questions you may have about hot tub chemicals.

Can You Use a Hot Tub Without Chemicals?

Simply put, no. Your hot tub needs chemicals to keep the water and your bathers safe. Without chemicals, your hot tub can become a breeding ground for bacteria and other harmful microorganisms. Above all, the water must be clean so sanitisers will keep bacteria levels down.

How Soon Can You Use Your Hot Tub After Adding Chemicals?

Wait until the chemicals dissolve entirely before using your hot tub. This can take anywhere from 15 minutes to an hour, depending on the chemicals you add. Read the instructions for the chemicals you add as some may require longer wait times.

Is Chlorine or Bromine Better for Sanitising a Hot Tub?

Both chlorine and bromine are effective sanitisers for hot tubs. Chlorine is the most popular and easy-to-use sanitiser. Bromine is suitable for those who like sitting at a higher temperature, as it stays stable even when the heat is up.

How Often Should You Change the Water in Your Hot Tub?

Change the water every 3-4 months, depending on how often you use your hot tub. If you use it frequently, you may need to change the water more often. Additionally, you should regularly test the water to ensure its safety.

Add chemicals directly to the water, not on the surface. Also, use the right chemicals for your hot tub and follow the manufacturer's instructions carefully. Remember to store hot tub chemicals in a cool, dry place and dispose of them properly.

To maintain a clean, safe, and well-balanced hot tub, you need a few essential chemicals. To keep your hot tub water clean and balanced, you need the following essential chemicals:

Sanitizers

Chlorine (Granules or Tablets) – Fast-acting and effective at killing bacteria.
Bromine (Tablets or Granules) – Gentler on skin, lasts longer in hot water.

pH Adjusters

pH Increaser (Sodium Carbonate / Soda Ash) – Raises pH if it drops below 7.2.
pH Decreaser (Sodium Bisulfate / Muriatic Acid) – Lowers pH if it rises above 7.8.

Alkalinity Adjusters

Alkalinity Increaser (Sodium Bicarbonate / Baking Soda) – Keeps alkalinity stable (ideal range: 80-120 ppm).

Shock Treatment

Chlorine Shock (Calcium Hypochlorite / Dichlor) – Removes bacteria and organic waste.
Non-Chlorine Shock (Potassium Monopersulfate) – Oxidizes contaminants without adding chlorine.

Calcium Hardness Adjusters

Calcium Increaser (Calcium Chloride) – Prevents foamy water and protects hot tub parts.

Can I have a hot tub without any chemicals?

It is not recommended to have a hot tub without any chemicals. Chemicals help to maintain the cleanliness and safety of the water.

How long do hot tub chemicals last?

The duration of the hot tub chemicals' life depends on various factors, such as the hot tub's usage, size, and the specific chemicals used. Generally, they last for a few weeks to a couple of months.

How often should I do hot tub maintenance?

Hot tub maintenance should be done regularly to ensure optimal water quality. It is recommended to test and balance the water chemistry weekly and perform a thorough clean every 1-3 months.

What is everything I need to know about hot tub chemicals?

Everything you need to know about hot tub chemicals can be found in a hot tub chemical guide or by consulting a hot tub owner. You should also understand how to properly test and balance the water chemistry and safely handle and store the chemicals.

Can I use chemicals in an inflatable hot tub?

Yes, you can use chemicals in an inflatable hot tub. Similar to regular hot tubs, chemicals are necessary to maintain the cleanliness and safety of the water.

What is a hot tub sanitiser?

A hot tub sanitiser is a chemical (usually chlorine or bromine) that kills bacteria and germs in the hot tub water. It helps maintain a safe and clean environment for hot tub use.

Can I use the hot tub immediately after adding chemicals?

No. Allow the chemicals to disperse and adequately mix with the water before using the hot tub. The waiting time can vary depending on the chemicals used, so refer to the product instructions before applications.

How should I store hot tub chemicals?

Store the hot tub chemicals in a cool, dry, and well-ventilated area. They should be out of the reach of children and pets and away from flammable materials.

How do I dispose of hot tub chemicals?

Contact your local waste management facility for guidance on properly disposing of hot tub chemicals.