How To Test Hot Tub Water For Bacteria (Here’s How…)

By James Brockbank •  Updated: 07/20/21 •  14 min read

How to test hot tub water for bacteria?

You can use test strips to test for chlorine or bromine, these are the chemical compounds added to kill bacteria.  The industrial test kit helps test both bromine/chlorine contents and the pH levels in your hot tub water. A digital test kit is commendable if you’re looking to get higher testing accuracy.

Stop wasting time and money with hot tub maintenance and confusing water chemistry! The Hot Tub Handbook and Video Course will help keep your hot tub balanced, sanitized, and crystal clear all the time.

Check out my list of high-quality hot tub products to help keep your hot tub clean and running great all year long!

My recommended product to help you test your hot tub or pool water for accurate pH, alkalinity, bromine, and chlorine readings is the AquaCheck Trutest Digital Reader.

The last thing you want to happen in your hot tub is the buildup of bacteria because they can affect your health and safety alongside your loved ones who will be using the facility.

For this reason, How to Test Hot Tub Water for Bacteria is a critical question because it is the pathway to your health and safety when you’re using a hot tub.

One of the strategies that will help keep your hot tub safe and clean is to kill any bacteria present in it. However, you can only kill bacteria once you have tested and established their presence.

In this article, I will talk more about how you can test for chemicals and bacteria in your hot tub water.

Let’s get started!

How Do I Know If My Hot Tub Has Bacteria?

If your hot tub water is cloudy or is foaming when the jets are turned on, then bacteria is forming in your hot tub water. This is a direct result of not enough sanitizer being present in the hot tub. The pH should be between 7.4 and 7.6. To sanitize, add 30g (1 capful) of oxidizer to the spa. Next, add another 30g of sanitizer (either chlorine or bromine) to the water. Sanitizer levels should be between 1-3 PPM for chlorine or 2-6 PPM for bromine. Let the spa mix and sit for 24 hours and check if the smell disappears.

I usually add chlorine or bromine in the hot tub to kill bacteria. The recommended time for adding either of the compounds is after testing for the required contents.

If I determine from testing that chlorine or bromine levels have fallen below the recommended levels, our hot tub water is possibly harboring bacteria. As you can see, there is no direct method of testing bacteria from your hot tub water.

I can only test whether the compounds responsible for killing bacteria are present. If they are, I assume that the water is safe and free from these pathogens.

However, lack of free chlorine or bromine in your hot tub water should raise the alarm and tell you that there are high chances of bacterial infestation.

Consider Using a Water Care Monitor

Monitoring the health of your hot tub can often be challenging if you are not testing the water on a regular basis. This can also be a problem if you go on holiday or you are unable to take care of your hot tub due to mobility issues.

A test system I highly recommend is the Exact Industrial Test System. This system is great for hot tubs and pools and gives your a highly accurate digital readout of your water chemistry compared to other methods.

The pHin Smart Water Care Monitor for pools, hot tubs, and inflatable spas continuously tests the water and alerts you when to add chemicals with the integrated mobile app.

This water care monitor also takes constant readings of the temperature inside your hot tub. This will give you peace of mind while away from your spa.

The mobile app will inform you when to add chemicals such as chlorine, and how much chemical is recommended. This is done by entering your hot tub or pool’s unique dimensions.

Simply scan the bar code of any chemical brand and the pHin app will calculate how much chemical is to be added to the water. Most products and brands are recognized by the application.

The pHin device will sample water more than 1000 times per week to give you an accurate reading compared to using test strips.

The pHin device works with different water types including chlorine, bromine, and saltwater hot tubs, swim spas, inflatable hot tubs, and pools.

This unique device comes with a lifetime warranty to ensure your water remains clear and ready for you to use at all times.

Testing Hot Tub Water With An Electronic Tester

An electronic tester is another option that hot tub owners can use in determining whether or not their hot tub water contains bacteria. The electronic test kit is recommended if you’re interested in getting highly accurate results regarding your hot tub water. Although these test kits are costly, they are highly effective because they reduce the risks associated with human errors when other testing procedures are adopted. 

The last option you can use in testing bacteria in your hot tub water is to hire a professional for the task. The professional will test the presence of Chlorine or Bromine in your hot tub water and inform you whether the facility is safe and free of bacteria.


How Do You Kill Bacteria In A Hot Tub?

Now that you have tested and established that your hot tub water is infested with bacteria, you need to kill these pathogens before you start bathing. Read on to find out how you can kill bacteria in a hot tub.


You can sanitize your hot tub using Chlorine or Bromine sanitizers. Bromine is a higher off-gassing and more likely to last longer when compared to chlorine. When you sanitize, you should not base on guesswork. I recommend the use of test strips to check the sanitizer levels in your hot tub water.

If you’re using a test strip, you should dip it into the hot tub water briefly and then compare the color on the color scale on the strip bottle so that you can see the amount of free chlorine or bromine.

When you’re starting to test for the sanitizer levels in the hot tub water, the color of your test strip will usually be purple. If the sanitizer levels are low or there’s no free sanitizer in your hot tub water, the strip will change to the light shade purple color or turn white.

Suppose your hot tub is using the latest technology, in that case, it is equipped with self-dosing dispensers that add chlorine or bromine after sensing that their levels have fallen beyond the recommended levels.

The dispensers have pucks and a design that allows the sanitizer levels to be adjusted into the hot tub water. I recommend monitoring the pH and the sanitizer levels on your hot tub to ensure it doesn’t get to levels that might cause you skin rashes. Ideally, the pH range of 7.2 to 7.6 is recommended.

On the same note, the recommended sanitizer levels should remain in the range of 1.5 and 3.0 ppm for chlorine. If you’re using bromine, keep it between 3.0 and 5.0 ppm.

Hot Tub Shock

Shocking your hot tub is an easy process that doesn’t require professional intervention. You’ll only need to have a chlorine or a non-chlorine shock, add it into your hot tub water, and leave it to kill pathogens in the water. The first step in shocking your hot tub is adjusting the pH levels of the hot tub water to the range of 7.4 and 7.6.

Ensure that your hot tub is not covered because you want to give it space to breathe when it’s being shocked. You should then turn the air to the jets off but ensure to leave the circulation pump running to ensure the water moves even though it will not be too agitated.

The amount of shock needed is determined by the number of gallons your hot tub supports; the information is available at the shock’s user guidelines. You should then add the shock in your hot tub carefully.

I recommended SpaGuard Enhanced Shock for dichlor chlorine shock.

Clean The Hot Tub

You can also clean your hot tub to kill bacteria. Cleaning will help you drain the hot tub water, inspect for the signs of scum and algae, and clean all the surfaces to eliminate the dirt that can harbor the growth of bacteria.

After the cleaning exercise, you’ll need to refill the hot tub with fresh water, free of bacteria and other pathogens. It’s a good practice to drain and clean your hot tub even if you use different methods of killing bacteria, such as shocking and using sanitization.

Soak the Filter in Chlorine

Your hot tub filters are responsible for trapping dirt and debris from passing into the water and other working components like the pump and heater. As dirt and debris accumulate on the filters, they can provide conditions necessary for the growth of bacteria.

If filters are not cleaned in the proper manner, they will still pass the bacteria into the hot tub water after you’ve placed them back.

I strongly recommend that you soak the filters in chlorine when cleaning to ensure you have killed any present bacteria—the appropriate dosage measuring 3 to 5 gallons of water and adding one teaspoonful of Dichlor granular chlorine.

You should mix the solution thoroughly before you immerse the filters for about two to four hours. The procedure will help kill all bacteria in the filters and ensure water safety when placed back into the hot tub.

To clean a hot tub filter you must remove the hot tub filters from the spa, rinse the filters with fresh water, apply a chemical soak, rinse thoroughly, and reinstall the hot tub filters into the spa.

I also recommend the Aquatix Pro Cleaner to get the job done right.

Clean or Replace Your Filter

The regular cleaning exercise or replacement of the hot tub filters can also help minimize the chances that bacteria will develop or accumulate in your hot tub water. Your hot tub filters will need replacement if it’s more than 12 months old or if it’s in bad condition. If the filter is still useable, use a filter cleanser in the recommended dosage by the manufacturer.

Immerse the filters for the recommended duration or overnight into the cleanser solution and rinse it thoroughly to eliminate all the bacteria. When you’re done, put back the filters in the hot tub and enjoy bathing.

Follow a Regular Maintenance Schedule

I would probably recommend a regular maintenance schedule as one of the best strategies to keep your hot tub free of bacteria. A regular maintenance schedule means knowing when to inspect your hot tub, filters, and other working components. You also need to know the right time to do a quick cleaning of the hot tub components and the time for a thorough cleaning.

Under a regular maintenance schedule, you should inspect and replace filters and other components when it is the right time and drain, clean, and refill the hot tub as needed. You also need to test and maintain the levels of chlorine or bromine, pH, and alkalinity. In other words, a regular maintenance schedule adheres to all cleaning and maintenance routines, which is an excellent way to keep your hot tub free of bacteria.

Drain the Water and Refill

You can also drain and refill your hot tub to eliminate any present bacteria. Draining the water allows for inspection of your hot tub and its components to ensure that algae and other elements are removed.

Draining the hot tub will also allow you to scrub any scum from the hot tub and its components. These elements can be good sites for harboring bacteria, which is why you need to drain your hot tub and ensure that they are removed if present.

After the hot tub is drained and cleaned, you should refill with clean or sanitized water and wait for the recommended duration before starting bathing. Some sanitizers do not work immediately; therefore, you should allow them some time to kill bacteria.

I recommend the Superior 1/4 HP Thermoplastic Utility Pump.

How Do I Test My Hot Tub Water?

Use a test strip by dipping it into the hot tub water to a depth of about 15 centimeters. Pull the test strip from the water and wait for the indicated time from the user’s instructions. The color of the test strip will change within the required time. Compare the color of the test strip to the color chart on the strip bottle. Each pack of test strips has detailed instructions and a color chart by the side of the bottle. The color chart will tell you whether the chlorine or bromine is within the necessary range. If not, you’ll need to adjust by adding as recommended and retesting until enough free chlorine or bromine is present in your hot tub. 

You cannot treat your hot tub water from bacteria if you don’t know how to test it. I have seen that testing the water is about checking the presence of free chlorine or bromine elements. If absent, it’s very likely that your hot tub water is infested with bacteria and requires immediate treatment.

I recommend these water test strips from JNW Direct Pool and Spa to test your water.

What Is The Most Accurate Way To Test Hot Tub Water?

Test strips are the most common way of testing the hot tub water but not the most accurate. If you’re looking for the highest accuracy, the electronic tester is your option. They reduce all the possible errors you could make when testing your hot tub water through other methods. 

The electronic tester is ideal if you’re running a commercial hot tub that contains an automated dosing system because it will accurately calibrate the dosing panel. The use directions will vary with the exact pool test being applied but will always be provided with the equipment.

Electronic test kits do not have calibration requirements but are highly accurate. They are not recommended for domestic uses because of their high costs. You can still use a digital test kit at home and get a reasonable accuracy on the Total Alkalinity, the pH, and free Chlorine or Bromine.

The digital test kit is similar to the test strip but has higher accuracy. Its color readings will tell you whether the free chlorine or bromine is low, high, or okay.

How To Test Hot Tub Water For Bacteria: Conclusion

how to test hot tub water for bacteria

I have mentioned that the presence of bacteria in your hot tub corresponds to the presence of free choline or bromine in your hot tub water. I use chlorine or bromine to kill bacteria in our domestic or commercial hot tubs.

If I test for chlorine or bromine and find that their levels are low, there’s a risk that bacteria have infested our hot tub water. You can test for free chlorine or bromine using a test strip and with a color chart.

For more accurate results, a digital test kit will be the alternative. You could use other methods to test for bacteria in your hot tub water, including the pool and spa kit, electronic tester, or hiring a professional to do the work for you.

You can tell that your hot tub has bacteria if it tests negative for free chlorine or bromine. However, you can respond to kill bacteria in your hot tub by sanitizing, shocking, cleaning the hot tub, soaking filters in chlorine, and cleaning or replacing your filters.

You can also eliminate bacteria by maintaining your hot tub or draining the hot tub water and refilling.

When testing your hot tub water, dip the test strip to about 15 cm and pull it out. You then need to allow enough time for the test strip’s color to change so that you can compare it with the color chart.

For the most accurate results, an electronic tester is the best way to tell if your hot tub has bacteria. However, it is most viable for commercial usage, but I recommend using the digital test kits for domestic hot tubs.

I hope you found this article on testing hot tub water for bacteria helpful.

Thanks for visiting

James Brockbank