Hot tubs are a great addition to your spa equipment. Most are inviting and clean, but if not well taken care of, they can harbor algae, nasty bacteria, and have a foul smell that is nowhere close to inviting.

You must use various chemicals to keep the tub and the water clean and free from harmful organisms. You should know which chemicals to use and when to use them to keep the water ready at all times.

Ensure you check the pH levels, calcium hardness, and alkalinity several times a week. If you find they need balancing, you should add balancers and other chemicals for hot tubs to keep the water clean. Are you worried about the chemicals and balancing? Don’t worry. You do not require a Ph.D. in chemistry to understand hot tub chemistry.

If you are new to owning and taking care of a hot tub, here are the chemicals used and what they are used for.

What chemicals Do I Need for a Hot Tub?


Your hot tub needs to be cleaned regularly to avoid build-up. You should clean the filter cartridges, plumbing lines, the shell of the hot tub and the spa cover. As a general rule, you should never use household chemicals to clean the spa as it may result in foaming.

The filter catches grease, dirt, twigs, and other impurities in the tub. Over time, the dirt and grease pile up and collects inside your filter. It should be cleaned and the dirt removed otherwise it will end up clogging and potentially blocking the filter, which could lead to contamination and growth of algae.

Use filter cleaners to break down the grime and grease in the cartridges and other impurities that collect in it.

Leisure Time A Bright and Clear Cleanser for Spas and Hot Tubs is one of the most used hot tub cleaners. It works by suspending contaminants and clumping them together so the filter can trap them.

The cleanser is specially made for use in hot water and works well with most sanitizers to keep your it clean and clear.

For filter cleaning, Leisure Time- Jet Clean does a great job keeping your cartridges and plumbing free of grease and dirt.


If you notice your water looks cloudy and is not as sparkling as it should be, chances are your filter is not working as expected. If the filter has no problem, you may be having water sanitation issues.

Some particles are too tiny to be picked up by the filter and they may find their way into your tub water, making it look cloudy and unappealing. If you use your tub for business purposes, it may look unhygienic to customers. For this reason, you’ll need to add clarifiers.

Clarifiers are positively charged polymers. They attach themselves to negatively charged particles in the water and, in the end, form big clumps that can be easily trapped by the filter.

Although there are several reasons why your water may be looking cloudy, spa filter problems are the main reason. Clarifiers offer a little help to filters with problems. Adding two cupfuls leaves your water looking sparkling clean!

However, you should take care not to use too much as they may have the opposite effect of gumming up your filter. If your tub water is clear, there is no need for clarifiers.

Rendezvous Spa Clarifier will restore the water to being sparkling and inviting. The chemical rapidly digests oils, lotions, and organics to prevent waterline buildup, improve filtration, and avoid clogged filters.


Balanced spa water should have all chemicals readings at a balanced range. This is not as hard as it sounds. Ideally, when the spa chemicals are imbalanced, parameters such as alkalinity and pH will be affected, which is not a good thing.

Balancing chemicals are meant to balance the range of the spa chemicals, determined by a Saturation Index Calculator.

Total Alkalinity and pH

Alkalinity is the level of salts- carbonates and bicarbonates- which affects the balance of the water by acting as a buffer to stabilize the pH.

pH is the acidity or the alkalinity of your water. The ideal pH ranges from 7.2-7.6. Anything above or below this is considered detrimental. A pH below 7.2 means your water is acidic, while higher than 7.6 means it’s alkaline.

Increasing and Decreasing

If the water is acidic, it can corrode and damage the tube’s inner parts, including the plumbing. On the other hand, alkalinity can lead to your water looking cloudy, scales, and stains. It can also indicate excess calcium in the water, which can start forming on the tub’s surface and in the pipes.

For these reasons, you need to increase or decrease the pH accordingly.

  • To lower your alkalinity, add a pH decreaser.
  • To raise your alkalinity, add an alkalinity increaser.

Of all balancing chemicals, a pH reducer is the most commonly used. This is usually because the alkalinity and pH of hot tub water tend to increase and a pH reducer decreases booth successfully.

  • If you need to lower the pH, use a spa pH decreaser
  • If you need to raise  the pH, use a spa pH increaser

Total Hardness

This is the level of calcium salts in the water that affects the balance and determines how much scaling there is and how corrosive the water is. When the calcium levels are peak, the water attains total calcium hardness. You’ll notice scales on the body shell of your hot tub, and the water will look cloudy.

If the water is too soft, the hardness level will be low, and it will be forced to draw from other minerals like iron, copper, and aluminum found in the parts making your tub. This could damage your tub.

To avoid this, make sure your hot tub calcium reading remains at 100-250PPM. If you notice low hardness, you can add calcium booster in the water.


We use sanitizers every day to kill germs, bacteria, and pathogens. A sanitizer kills the bacteria and harmful pathogens that find their way into the hot tub.

There are two main types of sanitizers;


Chlorine dissolves in water to form hypochlorous acid, which breaks down the bacteria and kills them. The hypochlorous acid reacts with other materials in the process and becomes deactivated, thus the need for constant treatment.

You simply add chlorine granules in the water and wait for them to dissolve and kill harmful bacteria. Chlorine is known for its stinky smell and irritating the eyes. This is because it dissipates and reacts with the waste products to form chloramines responsible for the smell. This is one of the primary reasons why people avoid using chlorine. To keep the chloramines at bay, you will need to add chlorine regularly or shock your tub to get rid of them.

You should never use chlorine tablets in a spa as they are usually too strong for spas, so they’re specially formulated for swimming pools.


People use Bromine tablets as sanitizers in the spa. The chemical works by ionizing the contaminants, thus breaking their chemical bonds. Unlike chlorine, which dissipates after reacting with the contaminants, a good amount of bromine can keep working for some time.

However, bromine also produces bromamines. These are not as destructive as chloramines, but they still reduce the working of bromine in your hot tub. Shocking is also the only way to get rid of them. Bromine tablets are also good sanitizers.

People are always arguing which sanitizer is the best for use in the spa. While both have the same purpose, they have differences.

Comparison Between Chlorine and Bromine
  1. Chlorine kills bacteria more quickly than bromine. Although bromine is very reactive, it does not match chlorine and thus kills bacteria much slower.
  2. At high levels, chlorine can be harsh on your skin, eyes, and hair. It can also cause breathing problems when chloramines linger in the humid air in the spa. Bromine is more gentle on the skin though it might be hard to wash off after soaking for long.
  3. You should use 1-3 PPM of chlorine or 3-5PPM of bromine.
  4. Chlorine dissipates quickly, becoming ineffective; thus, you should replace it often while bromine takes time to dissipate and kill bacteria for longer periods.

Make sure you keep a sufficient level of sanitizer in your hot tub. If they fall below the required, pathogens, bacteria, algae, and other contaminants may grow even in hot water and tightly closed tub.


Spa shock is somewhat a sanitizer but different from the normal spa sanitizers. It is used to clear out any pathogens or contaminants that the other sanitizer missed.


  • To clean out chloramines and bromamines formed after chlorine and bromine have dissipated.
  • Used to activate bromide salts into bromine. If you are using bromine tablets, you don’t need to activate them.
  • Supplementing your daily sanitizer after a heavy use like a four-person soak.
  • Killing algae, removing water discoloration, restoring clarity, removing bad odors, and solving other water problems.

Chlorine and non-chlorine shocks (MPS) are the most common because they are fast dissolving and work well with both chlorine and non-chlorine sanitizers.

Make sure you test your water balance first using test strips from a test kit before shocking and adjust it accordingly. Follow the instructions on the label regarding the dosage depending on the amount of water in your hot tub.

Specialty Spa Chemicals

These are all the other chemicals people use in the spa but do not fit in all the other categories. They include algaecides to kill algae and prevent them from growing in the tub, metal defenders to keep dissolved solids in solution, enzymes to digest natural oils, among others.

Aromatherapy scents fall in the specialty products category. Though they are not a need, you can add them anytime you take a soak. Also, there are scents explicitly for the hot tubs.

Can you go in a hot tub without chemicals?

You can decide to go without chemicals but it’s next to impossible to maintain a hot tub without hot tub chemicals. Pathogens and bacteria will definitely enter in the water. You’ll also leave skin, lotions, and makeup whenever you soak in the tub. You require the spa chemical to get rid of the dirt.

Alternatively, you can opt to drain and refill the water every two days which is not only expensive but also time-consuming.

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

Depending on the levels of the chemicals, you should wait for several hours to get in the tub. 6-8 hours are ideal but some chemicals like chlorine can take up to 24 hours. Use the hot tubs chemical testing kit to test for pH and chemical levels.

For a shock treatment, it can be as little as 20 minutes unless you used a chlorine shock. The only sure way to know how soon you can enter is to test the levels of the hot tub chemicals.

Are hot tub chemicals bad for you?

Hot tub chemicals make the water safe for you. Without them, pathogens, bacteria, and a lot of contaminants enter the water.. However, the hot tub chemicals have their disadvantages. For instance, chlorine causes respiratory problems, skin problems as well as eye and throat irritation. Bromine poses some risks too.

While they have a negative effect on your health, you can reduce the risk of these chemicals by shocking after each use, showering before and after use, use the minimum recommended amounts of hot tub chemicals, clean the filter and tub before or on the recommended interval, check and adjust the pH level daily, and change your water before or on the recommended intervals.


Owning a hot tub is more than just soaking in and relaxing after a long day. Of course, that is the primary reason to purchase a hot tub, but you need to take care of it and treat the water to ensure maximum benefits.

Hot tub water chemistry may seem hard to understand, but it’s easy when you are used to it. You only need specific chemicals to keep the water balanced and keep contaminants out. Use a test kit with test strips to test the water first before attempting to add any chemicals. Correctly balanced water will not only lack contaminants but also give you a perfect relaxation when soaking.