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How Do You Fix Biofilm in a Hot Tub?

By: Author Jeff Campbell

Posted on  - Last updated:

Categories Hot Tub Water Chemistry

Almost every hot tub gets biofilm. It’s a natural by-product of using a hot tub regularly. Unfortunately, you usually can’t see it. So, how do you fix biofilm in a hot tub?

Biofilm can be eliminated and prevented by balancing the water chemistry regularly, changing the water every 3 months, cleaning the filters regularly, and using a biofilm remover every time the water is changed.

But that’s just a quick glimpse at the problem and the solution.

So in this article, we’ll look at what causes biofilm, how to know if you have a biofilm problem, how to get rid of it if you already have it, and what the best products are for eliminating it.

Let’s get into it!

Ready to Spend Less Time On Maintenance and More Time Enjoying Your Hot Tub?

Let’s face it. Balancing the water, keeping a clean filter, dealing with rashes, and trying to figure out which chemicals to buy and add can make you feel more like a chemist than someone who just wants to relax after a long hard day!

That’s exactly why The Hot Tub Handbook and Video Course is so valuable!

This is from Matt over at Swim University and he developed it for people looking to save money, time, and frustration. His tips on chemicals can save you $100/year just by making sure you buy only what you need.

So if you’re ready to stop being confused or frustrated with your hot tub and start spending more time in it, check out The Hot Tub Handbook and Video Course.

Just click that link to learn more on their website.

How do you know if you have biofilm in a hot tub?

High levels of biofilm are rarely seen but will be evident if there has been an increase in the amount of sanitizer needed to keep the levels correct. However, a slimy film at the edge of the water can also indicate a biofilm problem.

Biofilm is made up of bacteria and microorganisms that collect in your hot tub every time you use it.

No matter how much you shower beforehand, there is always organic material like hair, dead skin cells, and sweat that get into the water.

Mixed in with things that fall in while you’re using the hot tub, such as bugs and dead leaves, this creates a slime that attaches itself to the sides of the tub and the pipes that deliver water to the jets. You will usually see this slime at the waterline.

If the spa water has foam or a slimy substance on the surface that remains after the jets are turned off, this is also a sign that the biofilm is building up. But most of the time you’ll never see biofilm. It’s in the plumbing lines.

But foam or hot tub slime doesn’t always mean you have biofilm!

Luckily, I covered all the different possibilities of what causes foam in this recent article. After all, pH being off can lead to that too. So before you try and solves the issue, you need to make sure you’ve narrowed it down to the correct one.

Just click that link to read it on my site.

Other signs of biofilm presence are cloudy or smelly water. This can also be caused by a chemical imbalance, so it is always worth testing the pH and alkalinity before jumping to conclusions.

The smell of bad eggs is most likely hydrogen sulfide (H2S) gas. This, in itself, is quite harmless and will disperse after a short while with the lid off.

However, the cause of this is usually the decay of organic matter, which leads us again to the presence of biofilm.

Is biofilm in a hot tub dangerous?

Biofilm can be extremely harmful to those soaking since it contains high levels of potentially hazardous bacteria. It can cause rashes, itchy skin, and if it gets into your eyes or ears, this can lead to infections. 

‘Hot tub rash’, as it is commonly known, is caused by pseudomonas aeruginosa, a bacterium that can be found in biofilm.

If you breathe in the bacteria, which is easily done as the jets produce tiny bubbles that become airborne, you can develop a condition known as ‘hot tub lung’. This is caused by a group of bacteria known by their acronym MAC.

This can lead to a bad cough or difficulty in breathing.

Other infections include Folliculitis and Legionnaires’ disease – both of which can be quite dangerous. Folliculitis is similar to hot tub rash but more severe, and Legionnaire’s disease is a form of pneumonia brought on by inhaling legionella bacteria.

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The buildup of biofilm also affects the performance of your hot tub.

This happens by biofilm clinging to the inside surfaces of pipes, reducing the flow. This can lead to the pump burning out if it has to work too hard to push the water through. Ultimately the warm water and dark spaces are the perfect breeding ground for the formation of biofilm.

As the slime builds upon the surfaces of your hot tub, this can cause discoloration and may be difficult to remove without some form of detergent.

Removing bacteria from your hot tub is an essential part of your routine maintenance.

Luckily, I cover everything you need to know about that in this recent article. I even cover the one thing almost every hot tub owner does that can lead to a serious infection!

Just click that link to read it on my site.

Does chlorine get rid of biofilm?

Chlorine alone will not get rid of biofilm in your hot tub, but it can help to prevent it. Chlorine is a sanitizer, and as such, it will kill off bacteria, but it will struggle to break through the thin layer of slime that forms over the biofilm.

But the best way to keep biofilm at bay is to prevent it, not get rid of it after the fact.

So to prevent it, balance your water chemistry a few times per week. Add chlorine (or bromine) to the water in small doses to maintain a level of 1 to 3 parts per million (ppm).

For chlorine, that’s about ¼ ounce or 1½ teaspoons of granules every 2 or 3 days in an average-sized hot tub. Checking and maintaining proper chlorine levels is one of the best ways to keep hot tub biofilm at bay.

And always test the water with test strips on a regular basis.

Bromine holds up better in the heat, so you can add it less frequently. Or do what I do and just 4-6 bromine tablets in a floater every 7-10 days. Set it and forget it.

You should also add a large dose of chlorine to shock the water once a week for average usage.

This releases the free chlorine, which is locked into the chloramines that form when the chlorine mixes with the oils, deodorants, perfume, etc.

Shocking the water will go a long way to killing off the bacteria that causes the problems associated with biofilm, but you need something to break down any slime that might be protecting it.

White vinegar will also do the trick. Read on to find out how.

How do I get rid of biofilm in my hot tub without draining it?

One way of getting rid of biofilm without draining it is to add 1 gallon of white vinegar to the water. The acid helps break down the slime that coats biofilm, making it easier for chlorine or bromine to eliminate the bacteria.

But it will lower the pH, so make sure to adjust the pH when you’re done.

You can use ordinary household white vinegar for this. It has a lot of uses around the home, so it is always worth keeping in, or you could try Lucy’s Distilled Vinegar from Amazon (click on the link to check the current price on Amazon).

This product is 5% white vinegar distilled with water.

Lucy’s Distilled Vinegar is natural and free from added chemicals. It is much purer than ordinary white vinegar, and this makes it super-effective at cleaning out your pipes.

It’s also great for wiping down the surfaces of the hot tub to get rid of any biofilm residue.

Read more about it in this process in my recent article. I go into much greater detail on everything including the 1 way adding vinegar can totally mess up your hot tub!

Just click that link to read it on my site.

What kills biofilm in a hot tub?

The best product to kill biofilm in a hot tub is Oh Yuk! Healthy Hot Tub Cleaner. Simply pour 8 oz into the hot tub every 3 months when draining the water. Allow it to circulate with the jets on for 1 hour, drain, wipe down, and refill.

CLICK HERE to see Oh Yuk! On Amazon.

I literally do this every 3 months like clockwork when I change my hot tub’s water. It’s the easiest way to get rid of it and prevent the formation for biofilm. Do know that your jets will typically time out after 15 minutes? So plan to restart them a few times over that hour.

First, take out your filter cartridge.

Then add around 8 ounces of Oh Yuk to the water before the tub is drained and then run the pump with the jets and water features on. This will circulate the water through the pump and pipework flushing out the biofilm.

After an hour or so you can then drain the tub.

Once the water is drained, clean the surfaces down with Lucy’s Distilled Vinegar, and then thoroughly rinse off the residue.

As part of your regular maintenance, you need to take out and clean the filter every 3 weeks anyway. Then I do a deep clean every 3 months.

But minimally go ahead and give your filters a good rinse in the kitchen sink with a sprayer. Then just put them back in once you’ve drained and started the refilling and reheating process.

Does biofilm affect the pH level in a hot tub?

In short yes, especially if it goes untreated for a long period of time.

If you have biofilm, when you add sanitizer or spa shock, the chemicals will immediately start to work on the biofilm. This causes them to break down faster than they normally would.

This in turn lowers the pH (making the water more acidic). So if you notice you are having to adjust the pH more than you used to, it could be because you have a biofilm problem.

Does biofilm cause cloudy water in a hot tub?

Generally speaking, biofilm, except in extreme cases, will never actually be seen.

So cloudy water is usually caused by a pH imbalance or high levels of calcium in the water. But also, generally speaking, non-chlorine shock usually leads to cloudier water than when using chlorine shock.

But biofilm is unlikely to cause cloudy water.

Does non-chlorine shock get rid of biofilm?

The short answer is no. Non-chlorine shock will work to reactivate the chlorine or bromine sanitizer that has turned into chloramines or bromamines. But it doesn’t affect the fresh water the same way as chlorine shock.

So in and of itself, it won’t stop biofilm bacteria from building up.

That doesn’t mean you can use a non-chlorine shock. But you’ll need to be diligent about changing the water regularly and using a product like the Oh Yuk! Healthy Hot Tub Cleaner on Amazon I mentioned above when you do your water changes.

That will ensure you never have a biofilm issue.

Final thoughts

Biofilm formation is something you need to take seriously if you own a hot tub.

Inviting friends and family over for a soak will not make you very popular if they go away with a nasty rash or a bad cough.

Luckily, biofilm buildup isn’t that difficult to control.

Just stick to a regular maintenance routine, check the water, add sanitizer, clean the filter and change the water when it’s time to do so.

Ready to Spend Less Time On Maintenance and More Time Enjoying Your Hot Tub?

Let’s face it. Balancing the water, cleaning filters, dealing with rashes, and trying to figure out which chemicals to buy and add can make you feel more like a chemist than someone who just wants to relax after a long hard day!

That’s exactly why The Hot Tub Handbook and Video Course is so valuable!

This is from Matt over at Swim University and he developed it for people looking to save money, time, and frustration. His tips on chemicals can save you $100/year just by making sure you buy only what you need.

So if you’re ready to stop being confused or frustrated with your hot tub and start spending more time in it, check out The Hot Tub Handbook and Video Course.

Just click that link to learn more on their website.

As an Amazon Associate, I may earn a small commission from qualifying purchases if you click on Amazon from my site and choose to make a purchase. You can read my complete affiliate disclosure for more details.

Jeff Campbell
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