Why Do Hot Tubs Foam? (and how to fix without draining)

why hot tubs foam lg

There’s nothing quite as relaxing as soaking in a hot tub and letting the warm water circulate around you. But sometimes, when we open the lid, we see a lot of foam. So why do hot tubs foam?

Here’s what I’ve seen:

Hot tubs can create foam due to an excess of body oils, lotions, body care products, or other contaminants in the water. But high pH or soft water (low calcium) can also lead to hot tub foam. Additionally, water that hasn’t been changed in over 3 months will be prone to foaming.

But don’t confuse hot tub foam with bubbles. When you turn on the jets, the water gets aerated, producing bubbles, which should disperse under normal conditions when the jets are turned off.

But that’s just a quick answer.

So in this article, we’ll get very specific about the difference between bubbles from the jets and foam. But we’ll also look at exactly what products we tend to put on our bodies that tend to cause the most foam.

And we’ll talk about how to fix it if you have this issue. And we’ll even get into the 1 way that works to get rid of it without having to drain your hot tub.

Let’s get going!

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.

How do I stop my hot tub from foaming?

To stop a hot tub from foaming, ensure the pH and alkalinity are correct and adjust as needed. But soft water can also lead to foam, so adding a water hardness increaser may be needed. Lastly, if the people who use the hot tub wear a lot of makeup or body lotions, have them rinse off before entering.

Foam on the surface often indicates that the pH is too high.

Start by testing the alkalinity, which should be between 80 and 120 parts per million (ppm), then test the pH, which should be between 7.2 and 7.8 ppm. Always adjust the alkalinity first because if this is outside those parameters, you will have difficulty balancing the pH.

To lower alkalinity and pH, you should add an acid such as sodium bisulfate.

My favorite pH and alkalinity reducer is by SpaGuard on Amazon. It’s an Amazon’s Choice product with hundreds of reviews, and almost every rating is 5-star.

Another cause of foam could be the low calcium levels due to soft water, which can lead to fittings corroding, so it is important to check to see what type of water you have.

Use hardness test strips to check the calcium level. If it is low (below 150 ppm), add a calcium increase to make the water harder. Always add in small quantities to avoid overdoing it.

My favorite product for increasing calcium is this one by Hot Tub Things on Amazon. Just click on the link to get the latest price.

How do I get rid of brown foam in my hot tub? 

Eliminate brown foam in a hot tub by first balancing the pH, which may be too high, and making sure to use a calcium reducer if the water is too hard. Brown foam is often caused by high pH and/or hard water, which can cause a chemical reaction between the chlorine and metals in the water such as iron.

But you can also add a product like Hot Tub Pool and Spa Defoamer by Essential Values on Amazon.

Before doing anything, you should try doing a double dose of hot tub shock. Not only will this kill off the chloramines or bromamines, but it can also help get rid of excess foam.

You can also use a pool net to skim off any excess foam floating on the surface.

Bromamines and chloramines are natural by-products of using chlorine or bromine sanitizer. As they sanitize your water, they get used up and convert into bromamines or chloramines which no longer are able to sanitize but can give false readings on a test strip.

Shocking the hot tub gets rid of them. But, in fact, you should shock the water once a week as part of your maintenance regime.

But foam, especially if caused by pH or calcium imbalances, doesn’t smell. If the water is cloudy and smelly, then you have another problem.

I described what you need to do if this is the case in a recent article. But it can be really unsafe to soak in. While oftentimes it requires draining and refilling, there is 1 trick that may work without having to empty the hot tub.

Just click that link to read it on my site.

But if all else fails, drain the hot tub and refill it with clean, fresh water. When it is drained, you should clean the sides and base of the tub with Windex or a similar product but make sure you rinse it off before refilling.

If you live in a hard water area and you have a water softener in your house, including the garden hose, you should turn this off when filling your tub.

Or use water from a hose that is not connected to it. 

My house has 3 hose spigots, and 1 is separate from the water softener system. Soft water is not good for a hot tub, and this may be the cause of foaming.

But excessively hard water isn’t great either. And if you have a water softener system you probably have hard water. So either way, if you have a foam problem, you may need to use a calcium (hardness) increaser or reducer.

Again, here are the Amazon links for both if you need them:

CALCIUM INCREASER on Amazon

CALCIUM DECREASER on Amazon

Will vinegar get rid of foam in a hot tub?

White vinegar can eliminate foam. However, vinegar and chlorine create a toxic gas when mixed, so always allow recently added chlorine shock or sanitizer to dissipate for 30 minutes before adding vinegar. Also, turn on jets to circulate and leave the cover off.

With the jets running, add 1-part white vinegar to 40 parts water, so for a large hot tub, add 1 gallon of vinegar.

You can also add baking soda to the mix. This will reduce the acidity and react with the vinegar to create fine bubbles that will dissolve the brown foam.

Baking soda will, however, raise the pH and alkalinity (alkalinity much more than pH). So always make sure and test the water and adjust as needed.

It’s all a question of balance and having good test strips on hand is essential to the ongoing maintenance of your hot tub.

I recommend Poolmaster 6-Way test strips available on Amazon – click on the link to check the latest prices.

Is brown foam in a hot tub bad?

Brown foam in a hot tub is bad and potentially unsafe to soak in. It is a sign that the water is getting full of total dissolved solids (TDS) and/or a chemical imbalance.

These are the contaminants that you, your family, and your friends bring into the tub every time they use it.

Things such as makeup, deodorant, body lotions, oils, and shampoo all add to the TDS content of your hot tub, and over time these build up to a level where, when the jets are turned on, foam is created.

This is because the air bubbles become encased in the dissolved solids.

In a recent article, I explained how hot tub foam builds up in a spa and what you need to do to prevent it. While we’re getting into some of that here, that article goes a lot deeper into the prevention of foam in the first see page place.

Just click that link to read it on my site.

Does hot tub defoamer work? 

Hot tub defoamer does work to eliminate foam in a hot tub without having to drain it. Hot Tub Pool and Spa Defoamer is made from hydrophobic silica, which safely and easily defoams a hot tub without altering water chemistry and without leaving any residue or cloudiness.

As I already mentioned, Hot Tub Pool and Spa Defoamer is a great product for getting rid of foam in your hot tub without using harsh chemicals. Check out the latest price here on Amazon.

This silicone emulsion is made in the USA, and it scores almost a perfect 5-star rating from over 1,700 reviews. For less than $30 a gallon, it’s good value too. For this, you should get 64 doses, lasting you a long time, well over a year.

Because it’s silicone-based, it won’t irritate the eyes and skin, and it’s so easy to use. You just add 1-2 ounces, leave the pump running to circulate the water, and the foam should disappear within 5 minutes.

Hot Tub Pool and Spa Defoamer is compatible with all types of sanitizers – chlorine, bromine, salt water, etc. – and it works almost instantly, so you don’t lose much spa time if you find foam in your tub when you remove the lid.

CLICK HERE to see the latest price on Amazon.

Did I cover all you wanted to know about why hot tubs foam?

There are several reasons why hot tubs foam, but it is usually associated with a chemical imbalance. This can be caused by the water itself or the biofilm created by what we as users bring in with us.

Either way, there are products you can use to get rid of foam, but the best thing to do is to keep the water clean and in balance. That way, you shouldn’t get any foam at all.

But sometimes, we have to drain and refill the hot tub to get rid of the foam.

If you’re wondering how often you should change the water in your hot tub, then take a look at this recent article. After all, keeping the water changed on a regular schedule is yet another way to prevent foam build-up.

Just click that link to read it on my site.

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.


Photo which requires attribution:

Day 231: Caffe Strada by Quinn Dombrowski is licensed under CC2.0 and was cropped, edited, and had a text overlay added.

Jeff Campbell

Jeff Campbell is a husband, father, martial artist, budget-master, Disney-addict, musician, hot tub lover, and recovering foodie having spent over 2 decades as a leader for Whole Foods Market.

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