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  • Writer's pictureAqua Warehouse

A Guide To Hot Tub Chemicals - Which Ones To Choose and How To Use Them

Updated: Jan 4, 2023

Do you own a hot tub, spa or Jacuzzi? Are you finding the chemical side of things somewhat confusing? Stop worrying! This guide is for you. Find out how the different chemicals you can put in a hot tub or spa affect the water and much more about hot tub care.

Why Do You Need to Use Chemicals for Hot Tubs?

There are many reasons why you might choose to have a hot tub. You might enjoy a relaxing soak in it with friends after a stressful week at work. You might want a long soak in a hot tub or spa at the end of a hard day.

Whatever your reason for having a hot tub, you must keep it clean and free from harmful bacteria. What chemicals for hot tubs do is avoid problems caused by bacteria. After all, you fill the hot tub with warm water, which is an ideal breeding ground for such things.

This is easy to do by adding various hot tub chemicals, but you have to get the optimal balance.

Before discussing the different additives you can put in your hot tub and hot tub maintenance, you need to understand some technical terms:

  • pH: the term pH refers to a measurement of how acidic or alkaline the water in your hot tub is. Ideally, the pH scale works between 7.2 and 7.6.

  • PPM (parts per million): this is a unit of measurement. It refers to how many unlike items are contained in a batch of similar items of the same size.

  • Total alkalinity: this indicates how much alkaline is in the water. When the total hot tub alkalinity is too low or too high, excess alkaline, or lack of it, affects the balance and hardness of the water in the hot tub.

  • Total hardness: this is the amount of dissolved magnesium and calcium in your hot tub water and indicates calcium hardness.

When Can I Add Chemicals to My Hot Tub After Filling?

It would be best if you waited until the water in your hot tub reaches a temperature of 80ºF (30ºC) before adding any chemicals. When the hot tub water is hot enough, the hot tub chemicals will dissolve better and disperse throughout the water.

Can You Go in a Hot Tub Without Chemicals?

You put sanitisers in your hot tub to kill any bacteria. Therefore, if you get in your hot tub before treating it with any hot tub chemicals, you put not just yourself but others at risk as well.

What Chemicals Are Needed For a Hot Tub?

If you want to kill bacteria in hot tub water, you need to maintain the optimal balance of chemicals. A wide range of chemicals are available, so what chemicals do you need for a hot tub?

pH Adjusting Chemicals

The optimal pH scale for hot tubs is 7.2 to 7.8 PPM. Readings over or under this indicate that the hot tub water is too alkaline or too acidic. If you don't maintain pH levels correctly, it could lead to skin irritation or cloudy water in the hot tub. Maintain the pH levels within the recommended range by adding certain hot tub chemicals such as a pH increaser.

A pH Decreaser Like Muriatic Acid or Sodium Bisulfate

Both chemicals lower the alkalinity. However, muriatic acid is very corrosive and can create toxic fumes. For this reason, most people choose sodium bisulfate as a pH decreaser. Sodium bisulfate is non-toxic, safe to use around family and pets, is fast-acting, and reduces the pH of your hot tub in a few minutes. How much ph decreaser you need to add to maintain optimal pH levels depends on the current pH level of your hot tub water.

pH Increaser Like Sodium Carbonate

You should put sodium carbonate if the pH level is too low and your hot tub water is too acidic. This pH increaser is also known as soda ash, a white anhydrous and hygroscopic powder that neutralises acidic water. One side effect is that it leads to cloudy water in your hot tub, which is not harmful to humans. But direct contact with the pH increaser powder or crystals could produce irritation, a rash, or a burn.

Total Alkalinity Increasers Like Sodium Bicarbonate

To raise the pH level and alkalinity, use sodium bicarbonate. It will also improve the clarity and stability of the hot tub water.


A sanitiser will disinfect the water in hot tubs, keep the water clear, and be fast-acting. There is a wide range of sanitiser products for spa and hot tub use. Most people use either chlorine or bromine. You can also use oxygen.


Bromine is the most widely used sanitiser for hot tubs and swimming pools. Bromine is very effective if you want to kill bacteria, but some people are sensitive to it.


Chlorine granules are the more traditional treatment for hot tubs and swimming pools. It is generally the cheapest option and very effective when it comes to killing algae. However, it does give off toxic gasses, which can cause skin irritation.


Oxygen is a popular alternative to bromine and chlorine. It is generally used because it is a milder solution and unlikely to cause skin irritation quite so much. You can buy oxygen tablets together with oxygen liquid to sanitise the hot tub water.

Should I Use Bromine or Chlorine?

Of the two sanitisers, bromine works better at higher temperatures. That makes it a better choice for hot tubs. However, chlorine will kill bacteria and any contaminants quicker than bromine. Bromine has a lower pH than chlorine, so it should help keep the overall chemistry of your water more balanced.

How Often Do You Put Bromine in a Hot Tub?

How often depends on how often you use your hot tub and your bathing habits. It could be daily, but it might also be every 2-3 days. The level needs to be between 3 and 5 parts per million.

How Often Do You Put Chlorine in a Hot Tub?

The optimum chlorine level in hot tubs should be around 3 to 5 parts per million. How often you need to put chlorine in your spa or tub depends on your bathing habits and how often you soak in it. For example, as part of your hot tub maintenance routine, you might need to put chlorine in it every day, or maybe every two to three days.

Non-Chlorine Shock

Give your hot tub shock treatments by giving it a quick super dose of shock treatment chemicals. You can shock with sanitising agents or non-chlorine shock treatment. Shocking hot tubs after a water change is the best option. Non-chlorine shock, however, doesn’t sanitise the water, but it will help with any clarity problems you might be having. Shocking should be part of your hot tub maintenance as often as you think necessary, either daily or after every session in the hot tub.

Sequestering Agent

Is your water red, brown, green, or orange? Then you need a sequestering agent to help remove any heavy metals or calcium from the water. You should also include this agent when you put water in hot tubs. Heavy metals common in water include arsenic, cadmium, chromium, copper, nickel, lead and mercury.


If the hot tub water is foamy, this product will reduce it temporarily. Foam is caused in the water by things such as lotions, cosmetics, and body oils. If you shower before you jump in your hot tub or follow a spa water care routine, it should help to reduce the amount of foamy water.


You add calcium if the magnesium and calcium levels are not correct in the hot tub water. If these are out of balance, it can lead to foamy or cloudy water, plus calcium hardness and scale build-up. You can purchase a calcium hardness increaser or decreaser to increase or decrease the calcium and eliminate the cloudiness.


Biguanides are alternative sanitising agents. They are popular with individuals who suffer from sensitive skin - instead of using chlorine or bromine to clean hot tub water. However, they are not compatible with bromine or chlorine, so you will have to switch your water sanitising systems entirely if you want to change. They do have one drawback. They are not easy to handle as other shock products.

Water Clarifier

You add a spa water clarifier to keep your hot tub water looking clear. It works by attracting particles of dust and dirt suspended in the water. The larger particles can then be captured by the tub filter as the water circulates.


You can use enzymes to reduce the chemical sanitisers used as part of your hot tub water maintenance schedule. These organic compounds accelerate chemical reactions. They rid the spa water of non-living organic materials such as body lotion, oil, cosmetics, hair products, or bodily fluids.

Filter Cleaner

An essential part of any maintenance is cleaning the hot tub filters. Purchase a specially formulated filter cleaning product to remove and loosen things such as dirt, hair, oil, and grime from the pleats of the filters. Then rinse each filter thoroughly with clean water.

Plumbing Cleaner

Your hot tub plumbing is at risk of clogging if not flushed through regularly. Flushing with clean water alone is ineffective. Use a plumbing cleaner to remove scale build-up, biofilm, oily residues, grime, and other contaminants from the spa water.

Testing Strips or Liquid Testing Kit

You use testing strips or liquid test kits to test and measure chemical levels, total alkalinity, and pH levels. These measurements will determine the quantity of each spa chemical you need to use.

How to Store Your Hot Tub Chemicals?

You want your hot tub chemicals to be easily accessible but at the same time out of reach of children and pets. Here are some storage tips:

  • Use a cabinet or container: It should be lockable, waterproof, and off the ground.

  • Chemicals for your hot tub should be kept dry and cool.

  • Store hot tub chemicals in their original packing as this will ensure you follow the instructions.

What Is The Shelf Life of Hot Tub Chemicals?

Hot tub chemicals do have a shelf life. On average, if stored correctly, they will last around five years.

Can Hot Tub Chemicals Be Stored Outside?

You can store hot tub chemicals outside, but they are sensitive to moisture and heat, so you must keep them in a dry, cool place out of direct sunlight.


Maintaining the life and quality of your hot tub is critical if you want to enjoy it to the full. Regularly inspecting it, cleaning it, testing the water, and maintaining the optimal hot tub chemical levels will ensure your hot tub is always in tip-top condition. All these steps are vital for a hot tub owner.

Frequently Asked Questions

What is the most important chemical in a hot tub?

In hot tub care, the most important of the spa chemicals is sanitiser (chlorine). It keeps your hot tub water clean and free from bacteria.

What is the safest hot tub chemical to use in a hot tub?

Do you have sensitive skin? Then biguanides are the best chemical to use in either spa or hot tub water. Otherwise, bromine and chlorine are other chemicals you can use in spa water as long as you follow the product guidelines.

What hot tub chemicals should I put in my hot tub for the first time?

When you use your hot tub or spa for the first time, you should add a sanitiser, either chlorine or bromine.

How long should I wait between adding chemicals in a hot tub?

It is best to wait for the chemicals to be thoroughly mixed into the spa water or hot tub water before putting any more. Never mix chemicals.

How soon can you use the hot tub after adding chemicals?

If you add bromine or chlorine, you should wait 12 hours before entering your hot tub. In the case of a pH increaser, pH decreaser, or calcium hardness increaser, you don't need to wait before using the hot tub.

How many days can you use a hot tub without chemicals?

It would be best if you never used a hot tub without any chemicals. Without any chemicals, bacteria could start growing within 2-3 days. Hot tub maintenance is crucial because bacteria can affect the pH balance and other aspects of the water. If your hot tub sees heavy usage, you need to check and balance the chemical levels more often than if you only use it occasionally.




Jess Court

I'm Aqua Warehouse Groups Marketing Officer - overseeing all things news worthy in the hot tub industry, with tips and tricks that are bound to make a splash.

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