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Hot Tub Chemicals Guide for First-Time Spa Owners

If you are a new hot tub owner, you’re very excited about the potential relaxing and fun times you will experience in the future using your hot tub! It’s beautiful and inviting. You look forward to soaking in it at the end of the day and chilling out with friends on the weekends. Because you don’t drain the water out each time you use it, like with a bathtub, it’s imperative to keep the water safe and clean. To have clean and clear water in the tub for you and others, you will need to spend some time maintaining it with the proper chemicals.

At Custom Backyard Spaces, we are experts on everything about hot tubs. We want to share our knowledge with you so you have the best hot tub experience possible. So, we put together a guide to chemicals for first-time spa owners in this article to make it easy to take care of the water in your spa.

Custom Backyard Spaces | Hot Tub Chemicals Guide

The Importance of Using Chemicals in Your Hot Tub

One of the most important things you need to do on a regular basis is to keep the water chemistry balanced to ensure that you have clear and clean water. The water in your spa tub should be balanced so that it isn’t too alkaline or too acidic, much like a swimming pool. Using chemicals ensures the longevity of your spa. Filthy water in your hot tub is a perfect environment for various organisms, germs, and bacteria to grow, which can damage the equipment and give you hot tub-related illnesses. When you neglect keeping the water safe by using proper chemicals, you will undoubtedly need to spend time repairing the tub.


The chemicals you will most likely need are:

  • Sanitizers - Granular Chlorine, Bromine
  • Balancers - pH and alkalinity increasers and decreasers
  • Clarifiers
  • Cleaners

Testing the Water

Over the life of your hot tub, you will test the water more than anything else. This is the only way you know whether the water contains any contaminants or what the chemical levels are. Always check the water before getting into the hot tub. If you find that the water is not balanced, add the appropriate chemicals and delay getting into the tub for 20 minutes. This gives the chemicals time to work. To test the water, you can:

  • Use spa test strips - quick and easy
  • Use a liquid test kit - more comprehensive results
  • Take a water sample to your local spa dealer

Collecting the Hot Tub Water Sample

It’s important to properly collect the water sample that you test. Do not take the sample near any of the jets. Try to get the sample from as close to the middle of the hot tub as possible.

  1. Use a clean cup or bottle.
  2. Hold it upside down so the opening faces the hot tub floor.
  3. Insert the vessel into the water elbow-deep.
  4. Turn the vessel right side up to collect the water.

Using Test Strips

Test strips check for the pH, alkalinity, and chlorine and are the easiest, most accurate method for testing the water in your hot tub because it’s easier to match up the colors. If you need to test for components such as iron, copper, and salt, there are specialty strips for those. 

Here is how to use testing strips:

  1. Collect a water sample
  2. Dip a strip into the water and quickly pull it out. The strip doesn’t need to soak.
  3. Hold it still for about 15 seconds. Don’t shake it.
  4. Compare the strip to the guide on the package to match up the colors.

Balancing the Water

Depending on the results of testing your water, you may need different chemicals. Test the alkalinity first because it will buffer pH.

The Total Alkalinity and Hardness

It’s essential to maintain a balance in the total alkalinity (TA) and total hardness (TH) in the water. Low levels of alkalinity lead to aggressive water while high levels can cause a calcium build up and create scale within a hot tub. The reading should be in the range of 80 to 120 parts per million (ppm). If your water is showing a low alkaline level, use an alkaline increaser. Diluted in water, an alkaline increaser will not raise the pH above its normal range. A proper TA buffers pH and helps prevent pH fluctuations. If your water is showing a high alkaline level, you will need to use chemicals such as diluted hydrochloric acid or sodium bisulfate.

The pH

The pH indicates how acidic or basic the water is. You want your water to be neutral (from 7.2 to 7.8) so it is safe to soak in. A low pH can irritate the skin and damage the spa. A high pH can also cause eye and skin irritation and cause the sanitizer to be ineffective. If you are using bromine, the ideal pH is 7.0-7.4. If you are using chlorine, the ideal pH is 7.2-7.6. If your hot tub water has a pH that is low, you will use a pH increaser. If your hot tub water has a pH that is too high, you will use a pH decreaser.

Sanitizing the Hot Tub

Sanitizing your hot tub helps keep it safe for you and your fellow hot tub users. The CDC recommends using either bromide or granular chlorine for sanitizing. Bromide is the most popular chemical used for hot water. It is effective and inexpensive and has a lower pH than chlorine. Additionally, it kills germs for a longer amount of time. Bromide should register 3.0 - 5.0.

But, if you frequently keep your spa uncovered, chlorine granules or tablets might be a better option. Chlorine is more resilient to UV rays than bromine and kills bacteria more quickly than bromine, but doesn’t last as long. Hot tub chlorine, when dissolved in the water, creates hypochlorous acid which reacts with bacteria in the water to kill the bacteria. Chlorine levels should be 1.5 - 3.0. Never use liquid chlorine in a hot tub.

Shocking the Water

It doesn’t matter which sanitizer you use, biological matter still builds up in the hot tub as you use it. A shock treatment once a week takes care of this problem by oxidizing the organics in the water so bacteria has nothing to feed off of. Shocking the water also helps get rid of sanitizer residue that lingers. We recommend that you shock your hot tub once a week. You can use either a chlorine-based shock or a non-chlorine shock.

Chlorine-Based Shock

A chlorine shock is both an oxidizer and a disinfectant. Use these periodically but not every time you need to shock your hot tub because these chemicals can be hard on your hot tub’s plumbing. Chlorine-based shock is best used when you first open your hot tub or when you change the water and when you are cleaning after a lot of people have been in the spa.

Non-Chlorine Shock

A non-chlorine shock doesn’t disinfect the water and kill bacteria. This type of shock is great at oxidizing other contaminants and cleaning the water. Use this shock on a weekly basis when you are using the spa regularly.

  1. After adjusting the pH level and alkaline level, turn off the air to the jets but leave the circulation pump running.
  2. Measure the amount of shock you need for the number of gallons of water in your hot tub. Check the shock’s label instructions to find this information.
  3. Add the shock to your hot tub carefully.

Clarifying the Water

When the water in your hot tub is cloudy, you may have a buildup of bacteria, algae, metallic particles, or a mix of all of these. Most of the time, you can correct this by balancing the sanitizers and cleaning or changing the hot tub filter. But, if these actions don’t do the trick, then look at using a clarifier. Clarifying the water eliminates bacteria, body oils, algae, and sweat. Hot tub clarifiers are designed to clear up cloudy water, increase the performance of your filter, and keep the pH balance intact.