How Do You Fix Biofilm In A Hot Tub (Here’s How…)

By James Brockbank •  Updated: 12/27/21 •  15 min read

How do you fix biofilm in a hot tub?

To fix biofilm in a hot tub:

  1. Add a strong cleaning solution to the spa and turn on the jets.
  2. Turn off the power and drain the hot tub.
  3. Clean the hot tub thoroughly and refill it with fresh water.

The best practice is draining and cleaning the hot tub when biofilm is present.

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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 spa water for accurate pH, alkalinity, bromine, and chlorine readings is the AquaCheck Trutest Digital Reader.

One of the hindrances to enjoying a hot tub in a cold season or the hot summer is realizing the presence of slime or biofilm. 

You cannot enjoy the comfort and relaxation you desire in such a situation. 

So, the question will be, how do you fix biofilm in a hot tub?

Biofilm accumulates excessive bacteria and grime over the water surface over time. It is usually a living, slimy bacteria formed from the combination of dirt, organics, and bacteria. 

The base of the grime formation could be dead skin cells, body oils, lotions, and cosmetics, among others, but it will usually spread on its own. 

Common hot tubs include poor water circulation, high bather loads, and inconsistent water chemistry. 

The biofilm formation can present a maintenance headache, especially for the new hot tub users. 

Fortunately, this article elaborates on some strategies you can use to prevent or remove formed slime or biofilm in your hot tub. 

Let’s get started!

How Do You Fix Biofilm In A Hot Tub?

You can fix biofilm by adding pipe cleaning products before you start draining. First, you should ensure that the jets are running correctly through the plumbing system before draining and refilling the hot tub with fresh water. Then, use a specialized hot tub filter cleaner to clean the filters thoroughly. 

Biofilm resists sanitizers. It is usually challenging to remove this substance once it forms in your hot tub. The foaming, cloudy water, and foul odors will withstand even the heavy doses of the potent and the regular spa shock. 

It will also help regularly do a deep cleaning on your hot tub to prevent biofilm formation. 

If it has affected the walls and steps leading out of the spa, it is best to scrub it off into the hot tub before draining to allow the sanitizer to kill algae and bacteria. 

Although cleaning is the best way to fix a hot tub biofilm, you can still use other enzyme-based water treatment products to protect the walls and the steps of your hot tub. 

Add line flush product to the water before draining. This would dissolve all the biofilm accumulated in the pipes. Allow the water to circulate for 30 minutes after adding line flush product. You will see foaming on the surface of the water, but this is normal.

Steps to Remove Biofilm From a Hot Tub

You may follow unique steps to remove biofilm in your hot tub, some of which come before while others come after draining, as explained below. 

Remove Filters and Clean Them

The first step is usually to remove and clean your filters. I would recommend using a specialized filter cleaner at this first stage to ensure that all bacteria and any other germs are killed. 

Scrub the filters gently using a brush if they were affected on the surface by the slime formation. After you’re done, leave them to dry as you work on other components. 

Add Biofilm Cleaning Solution to the Hot Tub

Adding a strong cleaning solution to the hot tub before draining will dissolve many of the organic compounds inside the hot tub’s plumbing. After adding this solution, drain the hot tub and clean it.

The best biofilm cleaning products include harsh oxidizing cleaning products, bleaches, and surfactants. Surfactants are derived from petroleum. However, not all these products can be used with a hot tub because they risk the users. 

For example, harsh chemicals and bleach are unsuitable for biological settings. At the same time, surfactants are harmful to the environment even though they are used in cosmetics and handwashing soaps. 

You might hear rumors about using some of these products with your hot tub for biofilm removal, but it’s good to know the implications on the users and the environment. 

The best and safest known products that experts advise using are yeasts derived from the microbes, which are formed by certain strains of the candida yeast. 

These forms of yeasts will boost the efficacy of the current chemical treatment, dissolve the stubborn biofilms, and lessen their toxicity and environmental effects. 

Drain and Clean The Hot Tub

Draining and cleaning the hot tub is probably the most straightforward approach. The first step in cleaning a hot tub is to clean the interior surfaces. 

You can use a sift rug to remove the dirt from the hot tub shell. 

When cleaning, be careful to the waterline where the build-up takes place.

Remove and clean spa pillows with mild soap in water or find an appropriate water cleaning product. 

Rinse thoroughly if you decide to use a soap solution to remove any soap residue because the rest of the spa will be sparkling. 

There are two methods on how to drain a hot tub. The first is to use a submersible pump to suck the water out of the spa. A 1/4 horsepower utility pump should do the trick. The second is to attach a hose to the drainage valve and let gravity do the work. It can take up to 2 hours to drain a hot tub. However, this depends on the size of the spa and the amount of water it holds.

Refill The Hot Tub With Fresh Water

After each of the mentioned components of your hot tub are fully clean, start refilling it with water. Then, turn the power on and switch on the jets to allow the entire system to run normally. 

You might consider putting on the cover for the hot tub to maintain the temperatures and heat faster. 

How to Prevent Biofilm 

You can best deal with biofilm in a hot tub through proactive and not reactive methods. Specifically, regular sanitizing, cleaning, and scheduled maintenance will help you deal with the hot tub slime. 

You also have the option to use products like Aquafinesse every week to enable you to break down the protective layer covering the bacteria, thus delaying the rate of biofilm formation. 

Also, consider using spa purge products like the Ahh-Some annually because they will help in preventing slime formation. 

Consider taking these basic maintenance practices because they will save you the troubles of dealing with the actual problem once it happens to your spa. 

I will share additional details on the measures you can take in helping maintain a clean and healthy hot tub.  

Balance Water Chemistry

Test the pH and alkalinity of your hot tub weekly to make the necessary adjustments. Aim to keep the pH levels between 7.2 and 7.6. if the pH falls below this level, it could be too acidic for the bathers or even the hot tub itself. Indeed, it will reduce the effectiveness of the sanitizer you’re using and cause cloudiness in the spa. 

At the same time, the average alkalinity range is between 60 and 120ppm. 

You will be checking whether your hot tub water is within this limit during the weekly testing. 

If the levels have fallen, make the necessary adjustment to keep them within limits. I also advise checking the alkalinity levels every time you add the sanitizer. 

Shock Weekly

Shock your hot tub water weekly using your preferred sanitizer to prevent the build-up of microorganisms and bacteria in the plumbing fixtures. Hot tub shock will allow the sanitizer (chlorine or bromine) to be more effective.

I recommended SpaGuard Enhanced Shock for dichlor chlorine shock.

Cover Your Spa When Not Using It

I recommend this measure because it will prevent the entry of foreign materials into the hot tub. Specifically, it will block the access of animal wastes, debris, and the entry of rainwater. As a result, the hot tub water will be much cleaner and clearer, with minimal risks of slime formation. 

Clean the Filters Regularly

For the health of your hot tub, I would recommend rinsing the filter every one or two weeks using clean water. Using a chemical rinse, you can also deep clean these components for at least a month. 

Dirt in the filters can act as an excellent harboring site for microorganisms and bacteria. Besides, it could be one of the main reasons your hot tub water does not clarify. 

Drain the water after 2 to 3 months

Conducting a deep and thorough cleaning is one of the best ways to remove all dirt and wastes. The recommended duration for cleaning the hot tub is usually at least 3 to 4 months. 

Cleaning at these intervals will prevent chemical build-up or encountering other issues associated with the prolonged stay of the hot tub without cleaning. 

How Do You Know If You Have Biofilm In Your Hot Tub?

It isn’t easy to notice a biofilm for many hot tub users. The simplest way to tell if your hot tub has a biofilm is to look for the slimy film around the hot tub. However, if you also notice that you are using more sanitizer than usual for your hot tub, it might be affected by the biofilm issue. 

Biofilm is a combination of microorganisms and bacteria accumulated in your hot tub because of its continued use. It doesn’t matter the effort you put in showering before getting into the hot tub because dead skin, hair, and sweat will somehow find their way into the water. 

When foreign matter falls into the hot tub, like leaves and bugs, the slime that attaches to the sides of the hot tub forms. 

It could also form on the pipes delivering water into the jets. This is usually visible at the waterline in the form of slime.

Another indicator biofilm could be building up is the water’s foaming at the surface even after the jets are turned off. 

Nevertheless, foam formation is not always a sign of a biofilm. For example, an imbalance in the pH levels can also cause foaming at the water surface, so try to narrow down and determine what is causing the foam before starting to fix the issue. 

Biofilm can also be detected from smelly or cloudy water, but these signs can also be indicators of poor chemical balance. 

Does Chlorine Get Rid of Biofilm?

No, chlorine does not eliminate biofilm but will help prevent it. Being a sanitizer, it will significantly assist in killing most of the bacteria that might be used in biofilm formation. Chlorine also struggles to break through the thin layer of slime that forms over the biofilm. 

The best way to keep biofilm from forming is its prevention rather than waiting to the point that you will have to get rid of it after it has developed. 

Do this by ensuring that your hot tub water chemistry is always balanced. 

Maintain bromine or chlorine levels at 1 to 3 parts per million, which is about ¼ ounce for chlorine or 1.5 teaspoonfuls of the granules. 

While you can add chlorine between 2 and 3 days, bromine can be added less frequently because it holds up better in heat. For example, I add 4 to 6 tablets in a floater in 7 to 10 days.

My recommended choice for hot tub Chlorine Tablets. These tablets come in different-sized containers based on weight.

My recommended choice for a hot tub chlorine tablet dispenser is this U.S. Pool Supply dispenser.


Is Hot Tub Biofilm Dangerous To People?

The hot tub biofilm can be dangerous, mainly because most of the bacteria it contains are hazardous. In addition, it can cause the user’s itchiness on the skin, rashes, or infections in the ears and the eyes. 

One of the problems that one can get from biofilm is “hot tub rash” caused by a bacterium called pseudomonas aeruginosa. 

Besides, you can breathe in bacteria through the tiny bubbles developed by the jets and suffer from a hot tub lung condition. 

Their acronym, MAC, knows the bacteria responsible for this condition. 

The symptoms of this condition are breathing difficulty or a bad cough. 

Hot tub biofilm can also cause other conditions like legionnaire’s disease and folliculitis. The latter is similar to the hot tub rash, but it is usually more severe, while legionnaire’s disease is a form of pneumonia infection. 

Is Hot Tub Biofilm Harmful To Equipment?

Biofilm affects the hot tub performance. It does so by clinging to the inner surfaces of the pipe, reducing the flow. Consequently, the pump might burn out for working excessively hard pushing the water. In addition, the continued build-up of the slime on the hot tub surfaces causes discolorations that are hard to remove without using detergents. 

An essential part of routine maintenance to avoid biofilm formation is to remove bacteria from your hot tub. Sanitizer kills the bacteria upon adding to the water. However, as it works on, its effectiveness reduces. 

How Do I Get Rid of Biofilm in My Hot Tub Without Draining It?

You can use vinegar, chlorine, or bromine to get rid of hot tub biofilm without draining it. The first step will be to add a gallon of white vinegar to the water because its acidity will help break down the slime that coats the biofilm for the bromine or chlorine to eliminate the bacteria quickly. However, be sure to recheck the pH after you’re done because it will lower its rating. 

On the same note, spa purge products can be added to prevent biofilm formation. There are specific products that will be added to eliminate and remove any potential slime in your hot tub. They activate a foaming agent to lift the biofilm from the plumbing surfaces. 

Add the purge product of your choice with the jets running for several cycles and ensure to allow proper circulation through the plumbing system. You might need to conduct several treatments in extreme cases, but it will ultimately work.

What Does Biofilm Look Like?

The definition of biofilm is “any group or microorganism or bacteria sticking themselves to the surface that is in regular contact with water.” It manifests in the form of a protective layer called slime. 

This layer tends to resist sanitizers like chlorine and bromine that would help in killing the bacteria. It can also discolor the waterline and hot tub surfaces, making cleaning easy. 

Biofilm is not visible, but it manifests through the indicated signs. 

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.

This mobile app is great if you’re wondering “does chlorine raise pH in a hot tub?” sometimes it’s not always clear.

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.

How Do You Fix Biofilm In A Hot Tub: Conclusion

how do you fix biofilm in a hot tub

If you have been wondering how to fix a hot tub biofilm, I advise sanitizers. However, it would help if you started by adding vinegar to break the slime protective layer of the biofilm before you proceeded to add the sanitizer. 

Removing the biofilm is not an easy task. Therefore, I would highly recommend taking protective measures through routine maintenance rather than waiting to deal with the problem. 

The biofilm is dangerous to the hot tub and the users, so do not wait until the problem forms in your equipment. 

Remember, the presence of a slime at the end of your hot tub is the simplest way to tell if it has a biofilm. 

I hope this article on hot tub biofilm was helpful.

Thanks for visiting

James Brockbank