9 Hot Tub Chemicals: Get Familiar with Maintenance Products

Published on

May 31, 2024

If you're a hot tub owner, you know the importance of keeping a chemical balance in your spa water. Not only is it crucial for the health and well-being of the users, but it can also impact the lifespan of your hot tub.

This article discusses how to properly balance hot tub water chemistry and the different types of chemicals commonly used in spas.

If you're looking for expert advice and science-based info on the most effective chemicals for hot tub maintenance, we have the answers below.

The Chemicals You Need For Hot Tub Maintenance

Hot tub water chemistry is essential to regular hot tub maintenance.

As there is a wide variety of products on the market, it is hard to understand what is essential and what is not. And, more importantly, when and how to use them.

This table lists the main types of spa chemicals and their purpose:

Type of Hot Tub Chemical Purpose
Spa sanitizer Kills bacteria.
PH balancer Balance spa water pH levels.
Hot tub shock Sanitizes hot tubs quickly and effectively, one case of extreme contaminant build-up.
Line flush cleaner Cleans the hot tub’s plumbing.
Calcium hardness increaser Increases the calcium hardness of the spa water.
Hot tub scale preventers and metal sequestrants Prevent hot tub deterioration and bacteria growth by preventing scale and eliminating metal residue.
Hot tub enzyme Controls organic contaminants and bacteria naturally.
Hot tub clarifier Keeps spa water crystal clear.

What Happens if You Don’t Put Chemicals in a Hot Tub?

Your hot tub[1] is not just an innocent sanctuary, it's also a breeding ground for algae and bacteria. It can leave your spa water green or cloudy, as the spas have the perfect temperature range to encourage these contaminants to grow.

Using your spa without chemicals can lead to various health issues, including fatal ones, such as Legionnaires' disease.[2][3][4]

1. Spa Sanitizers

When hot tub owners talk about keeping their spa water clean, they are referring to the process of sanitizing. Sanitizing hot tub water is important because it kills bacteria and other microorganisms that can cause illness.

The most popular hot tub chemicals are bromine and chlorine. Both come with advantages and disadvantages. The question of who would win the bromine vs chlorine battle has a simple answer: it depends.

Chlorine Sanitizers

Chlorine is the most popular hot tub chemical sanitizer used for hot tubs and swimming pools. It has powerful sanitizing properties and kills some pathogens, such as E-coli, in less than one minute.[5]

While chlorine kills bacteria and other microorganisms that can cause disease, it can also irritate the skin and eyes.

Here are some advantages chlorine has over bromine:

  • It costs less than bromine.
  • It kills pathogens quicker than bromine.
  • It leaves your hot tub water clear.
  • It is suited for outdoor hot tubs because it is not affected by UV rays.

Chlorine sanitizers come in various forms:

  • Chlorine granules. They are the most common type of chlorine sanitizer used in hot tubs.
  • Chlorine gas. It is generally used by professional hot tub maintenance companies, and it can be dangerous if used by untrained people.
  • Chlorine tablets. They are not as effective as granules because they don't dissolve evenly.

Sodium dichlore[6] is the most effective type of chlorine-based hot tub chemical and comes in the form of granules.

We recommend you keep chlorine levels around 3 ppm (parts per million) in order to maintain a crystal clear, safe, and comfortable spa experience.

Bromine Sanitizers

Bromine is a common sanitizer used in hot tubs and spas. Like chlorine, bromine is effective at killing bacteria and keeping the water clean.

Bromine has some advantages over chlorine:

  • It is less likely to cause skin irritation, making it a good choice for people with sensitive skin.
  • It is less likely to cause hot tub cloudy water.
  • It requires a less frequent application.
  • It's a great alternative for people allergic[7] to chlorine.

Bromine is available in both liquid and tablet form. Tablets are the most popular choice, as they are easy to use and last longer than liquid bromine.

Bromine tablets can be added directly to the hot tub or spa, or they can be placed in a floating dispenser.

We recommend keeping the bromine levels in your hot tub between 3 and 5 ppm.

2. PH Balancers for Hot Tubs

When your hot tub water displays too high or too low pH levels, it can harm both people and hot tubs. Here is where ph balancers come into play.

pH balancers adjust the pH levels of the water so that it is within the ideal range.

We recommend you use pH balancers as directed so that you do not end up with water that is either too acidic or too alkaline.

PH Balancers for Hot Tubs

What Is pH?

The pH measures how acidic or basic your hot tub water is. The pH scale goes from 0 to 14, with 7 being neutral. A pH lower than 7 is considered acidic, while a pH higher than 7 is considered basic. The recommended pH for hot tubs is between 7.2 and 7.6

What Is the Total Alkalinity of Spa Water?

The total alkalinity of your hot tub water is a measure of its ability to neutralize acids.

Alkalinity is important in spa water because it helps to buffer pH fluctuations, preventing the water from becoming too acidic or too basic.

The ideal total alkalinity for spa water is between 80 and 120 ppm.

There are three types of hot tub chemicals that help you reach a proper spa water chemistry balance:

  • PH increaser
  • PH decreaser
  • Alkalinity increaser

Hot Tub Water PH Up (PH Increaser)

The use of a pH up is essential because a low hot tub water pH is corrosive to the hot tub and can cause skin irritation.

Sodium ash is a common type of pH balancer. It is added to the water and, as it dissolves, it raises the pH.

Hot Tub Water PH Down (PH Decreaser)

PH decreaser solutions are acids that have a caustic effect. They are used because a high pH can make the water feel slippery and increase the chances of algae growth.

The most common pH-down solutions are dry sodium bisulfate and muriatic acid in liquid form.

Alkalinity Increaser

Low alkalinity levels in your hot tub can lead to a number of problems, such as pitting and corrosion of metal surfaces, staining of tiles and grout, and etching of concrete.

An alkalinity increaser helps stabilize your spa water's pH levels.

Most alkalinity increasers are made from sodium bicarbonate. Sodium bicarbonate is more than 1000 times less alkaline than sodium ash. As a result, it is used as an alkalinity increaser and not as a pH increaser.

3. Hot Tub Shock

A hot tub shock is a great saver for when the pathogens in your hot tub are at extremely high levels. Shocking is also known as oxidation.

The purpose of a spa shock killing algae, bacteria, and pathogens that can get the hot tub users sick. As a result, it must contain a fast-acting chemical in higher concentrations than normal.

Hot tub shock products come in two forms:

Using a hot tub shock helps because it:

  • Removes organic contaminants.
  • Kills bacteria, such as Legionella[8][9], Pseudomonas dermatitis[10], and nontuberculous mycobacteria[11][12].
  • Removes hot tub sanitizer waste products, such as bromamines and chloramines.

here is a list of the best types of spa shocks:

  • Dichlore
  • Calcium Hypochlorite
  • Lithium Hypochlorite
  • Potassium peroxymonosulfate

Do You Need To Add Shock After Filling a Hot Tub?

If you've just refilled your hot tub with fresh water, you may be wondering if you need to add shock. The answer is yes, you should always add shock to your hot tub, regardless of whether it's new or refilled.

Here's why: Shock helps to keep your hot tub clean by oxidizing organic matter in the water. Organic matter can lead to the growth of bacteria, so it's better to prevent it.

How often should I shock my hot tub?

The frequency with which you need to add shock depends on how often you use your hot tub. It's generally a good idea to add shock once a week.

If you're not sure whether you need to add shock, simply test the pH of your hot tub water using test strips[13]. If it's below 7.2, it's time to add shock.

4. Line Flush Cleaner

Line flush cleaners work by flushing out the lines that circulate the spa water. This is essential because dirt, grime, and mineral deposits easily accumulate inside the plumbing.

Some hot tub line flush cleaners need to be diluted with water, while others come ready to use.

We recommend using hot tub line flush cleaners every month to help keep the spa water clean and clear.

5. Calcium Hardness Increaser

A calcium hardness increaser raises the levels of your hot tub's calcium hardness.

Calcium hardness levels in your hot tub are important for several reasons.:

  • They measure the amount of calcium dissolved in the water.
  • If the calcium hardness level is too low, the water is more susceptible to changes in pH, which can cause problems with your spa equipment.
  • Low calcium hardness levels can lead to calcium deposits forming on surfaces such as tile and grout.

We recommend you keep your calcium hardness levels between 150-250 ppm.

6. Hot Tub Scale Preventers and Metal Sequestrants

The scale build-up indicates that there's too much calcium or magnesium in the hot tub water. When this happens, it leaves behind chalky deposits[14]. These deposits have a sandpaper texture which facilitates the development of bacteria.

Metal sequestrants are chemicals that bind to metal ions in water, which can then be removed from the water by flocculation or sedimentation.

These chemicals are often used in conjunction with mineral sanitizers, such as chlorine or bromine. They help reduce staining and scaling caused by metals in the water.

7. Hot Tub Enzymes

Enzymes are a natural way to control bacteria and other organic contaminants[15]. They work by breaking down the cell walls of bacteria, funguses, and viruses. This process eliminates the need for harsh chemicals, which can be irritating to sensitive skin.

The frequency of use will depend on the size and type of hot tub, as well as the number of users.

Hot Tub Enzymes

8. Hot Tub Clarifiers

Hot tub water clarifiers work by binding together small particles of dirt and debris, making them easier to filter out of the water.

The two main types of clarifiers are coagulating and flocculating. Coagulating clarifiers work by causing small particles to clump together, while flocculating clarifiers cause these particles to settle to the bottom of the tub, making them easier to vacuum out.

You should use a clarifier once every week or two, depending on how often the tub is used.

The root cause of cloudy water is usually improper pH levels or a build-up of oils and lotions on the surface of the water.

Hot tub chemicals can help restore clarity, but it's also important to be vigilant to maintain proper pH levels and avoid products that can cause scale build-up.

9. Hot Tub Filter Cleaner

Hot tub filter cleaners are specifically designed to clean hot tub filters, and they do an excellent job of removing dirt, grime, and other debris.

In addition, filter cleaners are also effective at removing scum and other build-ups that can clog filters and reduce their efficiency.

Expert Tips on how to use Hot Tub Chemicals

Step 1: Add chemicals that prevent stains or remove metal if necessary.

Step 2: Balance your hot tub's pH and alkalinity levels.

  • Add the product slowly and test the water regularly to make sure you don't overshoot the desired level of alkalinity.
  • Once you've reached the desired level, maintain it by regularly testing and adding more increments as needed.

Step 3. Regulate the sanitizer levels.

  • Check the level of sanitizer using a test strip. If the level is too low, add more sanitizer to the water.
  • Make sure that the pump is turned on so the sanitizer can circulate evenly throughout the tub.
  • Run the jets for a few minutes to help distribute the sanitizer evenly

Step 4. Balance the calcium hardness levels.

  • Test the water to see where it falls on the scale.
  • Add a calcium hardness increaser if the levels are too low or a decreaser if the levels are too high.
  • Add small amounts at a time to avoid sudden changes in pH levels.

We recommend taking a 20-minute break before adding different chemicals to avoid potentially dangerous chemical reactions. Also, adding chemicals when your hot tub is full and directly into the water is preferred.

Expert Tips on how to use Hot Tub Chemicals


A wide variety of hot tub chemicals are available on the market. These products work together to maintain your hot tub clean and prevent any build-up of bacteria or other threatening microorganisms.

Here at O-Care, we provide a reliable product to help you reduce the amount of sanitizer you put into your hot tub by 78%. It leaves your skin soft and you don’t have to shower after bathing.