What Causes Foam in a Hot Tub? How to Remove and Prevent It

Hot tubs are supposed to have gentle rolling bubbles, but you are not supposed to have foamy water. Why does this happen? Is foam in a hot tub bad? Hot tubs are comfortable and fun until excess foam takes over. With a little care, hot tub foam can be removed and prevented from occurring again.

A foamy hot tub is typically caused by common surfactants such as soap, hair products, and human body residues. Depending on the surfactant type and amount, the foam can become excessive. Fortunately, you can prevent and remove foam from hot tubs.

Perhaps a foamy hot tub looks like a bubble bath, but it is not as clean or safe as a regular tub. Foam in a hot tub when the jets are on is a clear sign that you need to clean your hot tub, and the faster you clean it, the better. Keep reading to find out why hot tubs foam, how to prevent foam, and how to get rid of it.

What causes foam in hot tub water?

While a foaming hot tub might seem harmless, it can signify some pretty nasty business. It may not be merely the relaxing bubble bath it looks like.

Hot tub foam is generally made out of three things:

• Water
• Air
• Surfactants

While none of those elements are individually a problem, when mixed with other residues, they create the foam that is a problem. The surfactants (soap, oils, etc.) are the culprits when making hot tub foam. Surfactants are sticky molecules that lower liquid surface tension and make it easier for oil-like substances to mix with water.

Now add the air jets of a hot tub, and you get foams. The jet pump is responsible for making tiny bubbles. With surfactants in the hot tub, however, the jet pump bubbles become covered in contaminants and are unable to pop, which is why the foam persists. 

Water is the world’s greatest solvent. This means the water in your hot tub easily absorbs all the chemicals and residues that enter it, including surfactants. 

A well-maintained hot tub has spa water mixed with calcium and sanitizing chemicals, which prevent foam. However, missing a few maintenance days or excess surfactants leads to foam build-up.

Below, you will find the main surfactant sources that can cause hot tub foam.

Haircare products	Body and face care products such as lotions, creams, deodorants, and powders are surfactants that can cause foam in hot tubs. Makeup also acts as a surfactant in hot tub water.
Body/skin products	Our washed clothes tend to hold onto some soaps, bleach, detergents, and so on. Our swimwear has soaps and detergents that mix with the hot tub water.
Soaps & detergents	Low-quality or excessively used hot tub chemicals can cause foam. Therefore, it is important only to use high-grade chemicals in appropriate amounts.
Drinks	Other substances can interact with the hot tub water. Substances from the air, nature, and so on mix and react with the hot tub water. If the total dissolved substances are high, this contributes to foaming.
Low-quality hot tub chemicals	The human body is obviously an unavoidable one, but the truth is that it produces many different things. Dead skin cells, fatty acids, and more are its byproducts. Nothing can be done about this, which is why sanitizing chemicals and proper maintenance are important for hot tubs.
The human body	Low-quality or excessively used hot tub chemicals can cause foam. Therefore, it is important to only use high-grade chemicals in appropriate amounts.
Other dissolved substances	Sugary and fizzy drinks can spill into the hot tub, causing the water to become imbalanced.

How to get rid of foam in a hot tub

As a long-term fix, you can remove hot tub foam by replacing the water with clean, clear water. You can also use temporary chemical fixes.

Test your hot tub water

Get the water tested. You need to know if the pH, alkalinity, and sanitizer levels are optimal. The test should also reveal the total dissolved solids level, aka the surfactants, of your hot tub water.

You can get the water tested by taking a sample of it to a pool and hot tub store or using test strips.

Knowing the chemistry of your hot tub water will give you key insight into what specifically is causing your hot tub to foam.

Drain and refill your hot tub

The best way to remove the total dissolved substance is to drain your hot tub and refill it again with clean water. If there is a very high amount of surfactants, you should also do a line flush and get the filters replaced.

When your hot tub is completely drained, it is the perfect time to do a deep clean. You can wipe the hot tub interior down with a hot tub cleaner or a homemade vinegar-water mixture. Then wipe away all traces of the cleanser entirely; any residues left will cause future foam again.

Use anti-foam chemicals

You can purchase anti-foam products such as Pool & Spa Defoamer. This chemical gets rid of foamy water quickly. It is a great fast option, especially if you want to use the hot tub soon and not go through the hassle of draining and refilling.

This anti-foam method should not be a substitute for draining and refilling. However, these chemicals do not address the root of the problem; they merely keep foams away for up to 24 hours.

How to prevent hot tub foam

They say prevention is the best cure, and that applies to your hot tub, too. It might seem extreme, but now that you know just what hot tub foam is, it’s worth going the extra mile to prevent it from occurring in the first place.

Here are some common rules or guidelines to stop a hot tub foaming.

• Everyone should shower beforehand
  You and anyone else who goes into the hot tub should shower beforehand. This is to wash off makeup, body oils, soap residue or cream residue, and other chemicals from the body.
• Pre-rinse bathing suits
  If worn, the bathing suits of anyone entering the hot tub should be well-cleaned and rinsed with fresh water. This will ensure that any extra chemicals such as bleach, laundry detergent, fabric softeners, and so forth are washed out and do not enter the hot tub.
• Do not let your head go underwater
  This is especially important for those who have long hair. Additionally, those with long hair should tie their hair up in a high bun. Wearing a cap or hat to keep the hair out of the water is even better. Beards, especially long beards, should also not be dipped into the water.
• Invest in quality hot tub chemicals
  Only purchase and use good quality chemicals. Ideally, buy hot tub chemicals from trusted brands.
• No eating or drinking in hot tubs
  Try not to eat and drink in the hot tub. Eating and drinking always come with the chance of spilling, which is not good for the hot tub.
• Regularly clean your hot tub
  Proper and timely maintenance is very important to prevent hot tub foam. You should regularly drain and clean your hot tub and change the water at least once every few months.
• Clean hot tub filters
  If you have more than one, make sure you clean your hot tub filter or filters regularly. They will be less effective if dirty. Although you can give them just a quick rinse with a garden hose, you should give them a thorough clean at least once a month. Read How to clean hot tub filters.

Is hot tub foam dangerous?

It is not the world’s end if your hot tub has foam. However, a foamy hot tub can mean it is not sanitized properly.

In some rare cases, hot tub foam can be pathogenic. To avoid risks, only enter your hot tub when it is clear of foam.

Foam in your hot tub

Milky-colored water and foam in a hot tub clearly indicate that the water’s chemical balance is not right. This will only get worse with time unless you treat it. This is not only bad for you, but with time, it is also bad for the hot tub itself. The walls will corrode and discolor.

Sometimes, water foam is also caused by bacteria build-up. This is called biofilm, which can be detrimental to both you and your hot tub. That is why you should test your hot tub water regularly and add chemicals such as chlorine or bromine to keep it balanced.

Foam in public hot tubs

Public hot tubs and spas are more likely to have high foam levels. Commercialized hot tubs, even with foam, might look cozy at first, but you should be wary because the foam probably indicates unsanitized water.

It is probably better to skip foamy public spas or at least take a good shower afterward.

Hot Tub Foam FAQs

Conclusion

You want your soaks in the hot tub to take away your worries, not add to them!

Now you know what causes foam in hot tubs. After reading this, you should know what to do next time your hot tub starts to foam. Remember that prevention is key, so do your best to prevent any contaminants from going into your hot tub.

Happy soaking.