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How to Get Rid of Foam in a Hot Tub

By Matt Giovanisci | Updated: May 11, 2018

A bubble bath may be one of those self-care things you live for, but relaxation is probably the last thing on your mind when your hot tub starts to get a little too bubbly for comfort.

Ruling out any devious kids or wayward bottles of shampoo, just what creates hot tub foam? Better yet, how do you get rid of foam in your hot tub?

To solve this frothy riddle, we have to take a trip to the ocean.

What Causes Foam in a Hot Tub?

Maybe you’ve seen sea foam for yourself. Maybe you’ve heard about it in fairy tales (The Little Mermaid, anyone?) or seen it in movies. Sea foam is fundamentally the same as hot tub foam, just with a slightly different chemical makeup.

For foam to appear, it needs three things: water, air, and surfactants. If you’re not a chemistry geek, surfactants are basically super-sticky molecules that reduce the surface tension of a liquid, which makes it easier for substances like oil and water to mix.

Whether it’s in the Pacific Ocean or your spa, water isn’t just good ol’ H2O. Sure, it might look crystal clear, but it’s actually stuffed with dissolved salts, proteins, detergents, and other organic compounds—many of which are surfactants.

So your spa contains water and some surfactants, even if you properly maintain your chemistry. But if you slip a little on your maintenance schedule or don’t clear the water after a big hot tub party, you might flip on your jets—unlocking that final ingredient—and find yourself with a foamy mess.

The actual process for forming bubbles is funny. Surfactants, while different from each other in many aspects, all have one end that is attracted to water and one end that is hydrophobic, meaning it is not attracted to water.

When you add air to the mix, the surfactant molecules organize themselves right on the boundary between air and water.

Because the surfactants often end up creating a thin layer of water in between themselves (remember, they want one end facing water and the other facing air), they tend to push the water molecule into a ball, and suddenly you have a bubble. The more surfactants you have, the more stacking you get, and the more bubbles you get.

The result? Foam. And a big bubble bath in your hot tub. Not cool.

The Main Surfactant Culprits

If you regularly maintain your hot tub chemistry, your spa water is thoroughly mixed with sanitizing chemicals and calcium, which help neutralize surfactants and prevent them from creating bubbles.

But if you miss even just a couple of maintenance days, surfactants build up from three main sources.

1. Personal Care Products

Makeup, conditioner, shampoo, mousse, hairspray, lotion, and deodorant can make your sanitizing chemicals work overtime and eventually wreak sudsy havoc. The more of these products you use—say, you have long hair that requires more styling products—the more likely it is that surfactants will build up in your hot tub.

Laundry detergent and soap are also major culprits. Yes, we need to wash our swimsuits, but any leftover detergent in the fabric can really mess with your water’s chemical balance.

2. Beverages

You might enjoy a glass of wine, a beer, a fancy tropical concoction, or even just a soda with your weekend soak. Nothing wrong with that, but you may want to keep beverages away from the hot tub.

Spilling alcoholic or sugary beverages in your carefully tended water can lead to foaming. Plus, who wants to clean up a sticky mess on the edges of a spa, anyway?

3. You

When you get down to it, the things the human body can produce are kind of gross. Oils and dead skin cells are all over us whether we like it or not. But that’s why we have sanitizing chemicals in our hot tubs.

If your sanitizing agents are overburdened with body oil and dead proteins, you’re probably going to have a problem with foam in your hot tub.

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A Warning About Cheap Chemicals

We all love saving money, but sometimes the savings just aren’t worth it. This is especially true with cheap hot tub chemicals. They may not be as effective or as concentrated as more expensive options, which means you’ll have to use more to make sure your hot tub is clean. Which means you have to buy more. And then you use more. It’s a vicious cycle.

Even worse, those cheap chemicals could actually cause a buildup of surfactants and a whole slew of other water chemistry problems. That means you’ll have to spend more money on corrective treatments, more time cleaning your hot tub, and less time actually enjoying it.

Good hot tub chemicals aren’t a splurge—they’re an investment. Get the best you can, and save yourself the headache. After all, a hot tub is all about relaxation.

How to Get Rid of Foam in a Hot Tub

Got foam? That’s OK. While clearing a hot tub full of foam may seem like an impossible, messy task, it’s actually pretty simple.

Test Your Water

Before you do anything corrective, test your water to find out what your pH, alkalinity, and sanitizer levels are, as well as check for total dissolved solids (TDS)—these are the surfactants. Knowing what your water chemistry looks like after foaming can help you understand how to avoid the problem in the future.

Another thing to note is low calcium hardness may cause foam in your hot tub. Low calcium can cause other problems, too, like corrosion and etching on your finishes, so it’s important to regularly test these levels as well.

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Drain and Refill

Once you’ve tested your water and made note of all the chemical levels, the best thing you can do to get rid of the foam is drain and clean your hot tub. If you have enough surfactants in your water to cause foaming, you may also need to do a line flush and replace your filters.

Since you need to drain your hot tub anyway, this is the perfect time to perform a hot tub deep clean as well.

Basic Steps to Drain Your Hot Tub

  1. Use a line flush product, as needed, according to the package directions.
  2. Remove the filters. Depending on how dirty they are, you can either clean or replace them. (If you’re not sure, it’s safer just to replace.)
  3. Turn off the power to your hot tub, disconnect anything electrical, and trip the breaker.
  4. Drain your hot tub using a sump pump or the drain plug.

Basic Steps to Clean and Refill Your Hot Tub

  1. Once your hot tub is entirely drained, wipe down the interior surface with a mixture of one part white vinegar to four parts water. Or you can use hot tub cleaner.
  2. Thoroughly rinse the inside of your hot tub and wipe it down.
  3. Make sure to remove all traces of cleaner. Otherwise, you’ll end up with foamy water again!
  4. Replace your filters.
  5. Refill your hot tub. We recommend you use a hose filter attached to your garden hose to prevent chemical impurities.

After you’ve drained, cleaned, and refilled your hot tub, test the water, add chemicals, and allow the water to circulate for at least a day. When the circulation is complete, test the water one more time to make sure it’s ready for soaking.

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For Quick Fixes: Anti-Foam Chemicals

Say you’ve got a party coming up and not enough time to go through all the steps to correct a foamy hot tub. You can buy a foam remover chemical, which will get rid of the foam in your hot tub almost instantly and can last for up to 24 hours.

Remember, foam remover chemicals do not address the cause of foam in your hot tub. It just relieves the problem for a little while. You’ll still need to drain and refill your hot tub to get rid of the foam for good.

Besides, knowing what you know now about the makeup of hot tub foam, do you really want to soak in that? Didn’t think so.

How to Prevent Hot Tub Foam

The best way to combat foam in a hot tub is to prevent it.

Recommendations for Bathers

Recommendations for Maintenance

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Leave the Bubbles for the Bathtub

Waking up to a foamy spa might feel a little nightmarish, but correcting foam in a hot tub is relatively simple. Once you have a clean hot tub and fresh water, preventing foam in the future will be easy. Just remember to avoid adding things that make your sanitizing chemicals work overtime and keep a regular maintenance schedule.

These simple steps mean more time to spend in your relaxing, foam-free hot tub.

Happy Soaking!

Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
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