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What Causes Foam in a Hot Tub?

Find out the different foaming solutions to keep your hot tub clear and clean. We've also discussed what causes hot tub foam and how to get rid of it to avoid unpleasant soaking encounters.

Woman relaxing in the hot tub.

Have you ever turned on your hot tub, walked away for a minute, then returned to a bubbly mess? Well, you’re not alone. Hot tub foaming solutions are among the most searched for spa problems.

Fortunately, this seemingly major issue isn’t a major issue at all, and it can be readily solved using a variety of approaches. Once you know what causes foaming, you can take steps to restrict its entrance to your water and apply the right products to eliminate it.

In this article, we look at how foam appears in a hot tub and the possible solutions to it.

What Causes Hot Tub Foam?

Close-up of foamy water in a hot tub.

When the total dissolved solids (TDS) in your pool build up so that it is carried to the surface by either the blower or the air pumped through the jets, it leads to hot tub foam. The dissolved solids come to the surface with the air bubbles, which you usually see as foam.

Many things can cause high TDS levels. A lot of dirty stuff can enter the tub from your body, including dead skin cells, soap residue, skin lotions and cream, hair spray, and underarm deodorant.

Your filter will catch some of this small debris, but most of it will dissolve in the water. Also, every time you add a chemical to water, you put more solids into it.

The point when water becomes saturated depends on how much material is in the water and the flow speed of the jets. The foam will be the first thing you notice as this begins to happen. When it hits its saturation point, the water will become permanently cloudy.

Foaming Culprits and How to Avoid Them

Foam floating in the hot tub.

Some foaming factors are more problematic than others, reducing surface tension to achieve a soapy experience. Because you don’t want this to happen, you need to figure out why you have foam and take the appropriate procedures to get rid of it.

Foreign Residues

Soaps, moisturizers, beauty goods, hair products, sweat, skin oil, dead skin cells, organic elements that may have blown into the water, and so on are all examples of foreign residue. It also comprises any beverages you drink while soaking in the tub. Both sugars and alcohol can behave as a surfactant.

WHAT YOU CAN DO: The most popular causes of foam are also the most difficult to control. Extra rinse cycles on your swimwear and rinsing off your body and hair before entering the tub can help. It’s also important to avoid spilling your drink.

Low Calcium Levels

Low calcium causes soft water and weakens the surface tension. It is also quite destructive to equipment in the years ahead, so you must maintain proper calcium hardness levels in your water.

WHAT YOU CAN DO: Weekly hardness test strips can monitor these levels, and add chemicals that maintain appropriate calcium hardness as needed.

Overly High Or Low PH Levels

Unbalanced water may also cause a frothy spa experience. Many factors can cause pH levels to fluctuate, and treating the water on a regular maintenance schedule is a good way to keep it clear, clean, and balanced.

WHAT YOU CAN DO: Utilise pH test strips to check your water weekly, shock the water weekly, and use pH increasers as well as decreasers when required.

Getting Rid of Heated Hot Tub Foam

Close-up of water bubbles in a hot tub.

The following control recommendations are excellent ways to stay informed about why a hot tub may be foaming and avoid or cure the cause. Of course, you won’t know which of the above possibilities is the cause straight away or if you’re dealing with a combination of issues. Start with the basics to narrow down your problem.

Test Your Water

You should check pH, alkalinity, and sanitizer levels. These can help you determine whether your problem stems from an imbalance or something else entirely. You can also test for TDS to see what you put into your spa with each soak. Check for calcium hardness as well.

If you see these levels are out of whack, try changing them to see if that’s the problem. Testing and adding may take a few tries to get right, prompting you to contemplate a full tub drain.

Drain and Refill

If your water is foamy, you may want to drain the entire tub, rinse it out, and refill it. This approach allows you to start over after removing any surfactants and concentrating just on the chemical levels. Test your chemical levels again after you refill your tub, add chemicals, and let it settle to test for low calcium or pH level variations.

Don’t Use Inferior Chemicals

You want high-quality products with a dedicated customer base and positive ratings originating from reputable sources. Cheaper choices may contain fillers or less active chemicals, and they may not work as stated. You want options that are good for disinfecting and resetting imbalances, not just because they look nice in a bottle.

Use Antifoam Chemicals

If the above seems like too much trouble and you were looking forward to a relaxing soak, there is a quick fix. Chemicals that remove foam operate instantaneously and last for around 24 hours. They don’t fix the source of the problem, but they can help you recover from your first experience with foam and give you time to handle the issue without jeopardizing your soak.


Hot tub in the backyard surrounded by pine trees.

If you’ve been wondering why your hot tub is foaming, you need to figure out the cause and start treating it right away to avoid unpleasant soaking encounters. Many factors can create foam, but the typical cause is too many soluble materials introduced into the water each time you use your hot tub. The good news is that once you figure out the cause of your problem, it’s usually easy to fix!