Hot Tub Chemistry Detailed Guide


Hot tub chemistry. It may sound daunting, especially for the new hot tub owner. However, if you want to ensure that your hot tub’s water is clean and ready to use whenever you want to, then you’ll have to learn how to manage the water chemistry in your hot tub. Don’t worry, it’s actually pretty easy and anyone with the right knowledge about hot tub chemicals and how to use them can do it (and no, you don’t need a lab coat for this).

Hot Tub Sanitizers

Hot tub sanitizers kill bacteria and purify the water in your hot tub, making them a critical component in keeping your hot tub clean and ready for use. There are various types of hot tub sanitizers available and you can get these from your local pool supplies store or online. The choice for which sanitizer to use for your hot tub will generally depend on you, although some factors need to be considered especially since each hot tub sanitizer has its own pros and cons.


Chlorine is one of the most common types of hot tub sanitizers available, and though they’re great for swimming pools, they can’t be used as a standalone sanitizer for hot tubs. They need to be paired with a mineral sanitizing system for them to be truly effective in getting rid of dead organic matter and clear up cloudy water.

Chlorine also isn’t available in tablet form, which means that they dissolve much quicker than other sanitizers that are in tablet form when mixed with water. Because of this, you may need to add chlorine to your hot tub water more frequently, which can be a hassle for many busy hot tub owners.

Besides, you need to be careful when using chlorine. Putting too much chlorine in your hot tub can lead to bleaching and damage things that come in contact with it like your spa cover or your swimsuit.


A great alternative to chlorine is bromine. Unlike chlorine, these hot tub sanitizers are available in tablet form which is inserted into a floating bromine feeder in the hot tub. One advantage of this system is that it provides you with a non-stop flow of sanitation into your hot tub.

Chlorine and bromine are somewhat similar to each other from a chemical perspective. However, the way they react with water is what generally distinguishes them from each other. In a hot tub where the water temperature is usually high, chlorine tends to have a shorter lifespan, whereas bromine is much more stable and can last longer.

Bromine has been slowly becoming more and more popular than chlorine as a hot tub sanitizer over the years. One reason for this is that bromine doesn’t have a strong smell like chlorine. It also doesn’t irritate the eyes and is much gentler on the skin.


Minerals are great alternatives to chlorine and bromine and are quickly becoming popular nowadays. Some of the reasons why this is so are because mineral sanitizers are cost-effective and lessen the need for chlorine. These types of sanitizers use copper, silver, and other minerals to kill bacteria and purify the water. However, it’s not as aggressive as chlorine and can be slow to take effect. This is why you need to add a little bit of chlorine as a backup in case the minerals don’t kill all the bacteria fast enough. The chlorine also helps to give the water a fresh smell, without which the water would smell stale.

Whichever sanitizer you chose to use, make sure to look into any option closely to make sure it is the most suitable for you and your hot tub.

Hot Tub Shock

When you shock dose your hot tub, you add a high quantity of chlorine, bromine of non-chlorine shock. In general, raising the usual quantity by five to ten times should be enough, but do note that there are other considerations when it comes to shocking your hot tub.

The larger than usual dosage helps to kill any bacteria that may be present even after the addition of hot tub water sanitizers. It also helps to break down organic compounds (e.g. dead skin, oil, cosmetics, etc.) which can quickly accumulate in the water especially if the hot tub is used extensively. Shock dosing your hot tub also helps to convert chloramines (used chlorine mixed with organic waste that produce strong chlorine odor) back into active chlorine to help clear your water and restore the effectiveness of the sanitizer.

Regardless of what type of sanitizer you use in your spa, we recommend shock treating at least once a week to maintain the cleanest clearest water possible. Regular shock treatments will also ensure the best performance from your sanitizer.

Hot Tub pH and Alkalinity


To keep your sanitizer at the right level and working efficiently, you need to keep your water’s pH balanced. pH is a measure of the acid or base of a solution, and alkalinity helps keeps your pH from changing drastically. Low pH and alkalinity will cause damage to your hot tub, especially to your heater because of the acidity of the water. High pH and alkalinity will cause scaling which leaves a milky residue around anything the water flows through. Whether you have low pH and alkalinity or the other way around, your hot tub heater is at risk both ways as the acid will eat away at the heater element and the high pH will cause a scale around it which will make it work harder to heat your hot tub.

If both your pH and alkalinity levels are low, just adding alkalinity will increase both, but make sure to adjust the pH if the alkalinity doesn’t bring it up to the desired level. If both your pH and alkalinity levels are high, use pH decreaser to bring it down back to the right level.

These two chemicals are extremely important in maintaining balanced water chemistry in your hot tub. It’s important to keep a close eye on these levels by testing them frequently because the pH and alkalinity levels in a hot tub tend to fluctuate a lot.

Calcium Hardness

Calcium hardness (also referred to as total hardness) is a measure of the amount of dissolved calcium and magnesium in the hot tub water. The basic recommended range in a hot tub is between 200 and 400 parts per million. However, this can vary depending on the situation and several factors. For instance, the range can either go up or down depending on your hot tub’s finish. The chemicals you’re using to treat your hot tub water will also affect the calcium hardness level.

Another factor in determining hardness levels is water temperature. The colder the water, the more calcium is needed. Several problems may arise if your calcium hardness levels are too low or too high.

If your hot tub’s hardness level is low, you can experience plaster etching, equipment, jet, and plumbing corrosion. If your total hardness is too high, the hot tub water may not be able to hold all the minerals, and calcium can fall out of the solution, causing scale buildup and cloudy water.

Experts recommend that you test for total hardness at least once a month. It’s rather pretty easy and you can do this using test strips and kits which you can buy from your local pool supplies store. Doing so will protect your hot tub and prevent unnecessary expenses for repairs down the road.

Tips for Safe Hot Tub Chemical Handling

Just like any other chemical, hot tub chemicals need to be handled with care since improper handling and use of these chemicals can lead to injuries and other health hazards. Here are some important tips and considerations to keep in mind when dealing with hot tub chemicals.

  • Although hot tub chemicals are generally safe and approved for use by the public, you should still consider wearing some form of protective clothing like gloves and protective eyewear to protect against splashes and a mask to protect against fumes. These needn’t be special or expensive. You can use any regular kitchen rubber gloves and a handkerchief wrapped around your nose and mouth when using these chemicals.
  • Be sure to read the label on the box or bottle before using any type of hot tub chemicals and follow the instructions carefully.
  • Never mix hot tub chemicals unless instructed to do so by the manufacturer or a hot tub technician.
  • Be careful of using powdered hot tub chemicals when there is a strong wind blowing.
  • Wash your hands thoroughly after using hot tub chemicals.
  • Store hot tub chemicals in recommended storage areas, away from heat and moisture, and keep them out of reach of children and animals.

Globo Surf Overview

Keeping your hot tub water balanced is one way of ensuring that it’s safe and always ready for use. As can be seen above, this really isn’t that difficult, and the more often you do it, the easier it becomes. To properly balance your hot tub’s water, you’ll need to have at least some basic knowledge about hot tub chemicals and hot tub chemistry. By applying such knowledge, you can now go ahead and enjoy soaking in your hot tub without having to worry about any dangers or health hazards that are usually caused by unsanitary and unbalanced hot tub water.

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Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!