What Causes Foam In A Hot Tub?

Nothing beats having a good soak in a hot tub after a hectic workday. You can light up some scented candles and play good soothing music in the background. It will be your “me” time to pamper yourself.  You deserve something like this, after a day full of stress. You get home from work, eager and ready for the hot tub. Instead, you are longing so much to dip into your pleasurable bath only to see a very disappointing sight – a hot tub full of messy foam! The feeling of frustration will further seep into you.

What is this foam in the hot tub?

How can you prevent this foam from showing up in the water?

These are the questions that will immediately come into your mind. However, you need not worry as simple steps to solve the foam problem. You may reschedule your hot tub escapade for another day. To answer those questions and provide you with some helpful tips on getting rid of hot tub foams, you may read through them below.

What is hot tub foam?

Hot tub foams are barriers that surface when water, air, and surfactants collide. It results in a frothy bubble formation resembling foam. Surfactants are molecules that come from residues of chemicals. This hot tub foam can occur in different forms, all of them creating a soapy look on top of the water, making it cloudy and murky white in appearance. Generally, foam is not harmful to humans, but it can also cause some ill effects on your tub and is unhygienic.

What causes the hot tub water to foam?

Technically, surfactants reduce the surface tension of water. As a result, water and oil mix faster and form a thin “skin” on the surface. As the jet starts, the air joins the combination of elements, and this is when the water can start to form bubbles. As these bubbles group together, they become foamy in texture and appearance.

There are several reasons why foam surfaces on the water in your hot tub. A most common cause is failure to clean and sanitize your hot tub or spa regularly, especially after some heavy use, like a hot tub party. TDS or surfactants will build up and can cause foaming in the water.

Another cause of foam will be the many elements in our skin, hair, nails, and toes. These are the shampoo, lotions, cleansers, makeup, oils, and creams that we use. Even our bathing suits have laundry detergents whose remnants get washed off in the hot tub. We also shred dead skin cells naturally once our skin gets soaked and dipped in water. All of these are called TDS, or Total Dissolved Solids. They leave residues in the hot tub water that clog the air jet filter. If not cleaned properly, they will resurface above the water on your next tub’s use, thus the presence of foam.

Another possible reason for the foam in hot tubs is the leftover food crumbs and drink spills. Ideally, food and beverages are a no-no in the hot tub as these food and drink particles can contaminate the water and cause foam. Therefore, the best rule of thumb will be to avoid eating and drinking in the hot tub.

When you opt to use low-priced chemicals, it can also be the reason behind the hot tub foam formation. Unfortunately, these chemicals can also cause stains and corrosion in your tub. Make sure to go for quality brands that may cost a bit more but can be a wise investment in the long run.

Mother earth can also have a role in the hot tub foam formation, especially for outdoor hot tubs or spas. These natural contributors can be the falling leaves and other debris from the environment that can decompose in the hot tub. You need to have the hot tub covered when not in use, removing the cover occasionally to let the water breathe. Also, changes in weather temperature can bring about the presence of bacteria and algae. You can remove these substances with a regular cleanser and sanitizer.

How can we eliminate foam?

You may do the following steps to clear out the foam from the water in your hot tub.

  1. You may start with draining the water from the hot tub.
  2. Then, you can clean the hot tub filter to get rid of all dirt and contaminants. It will be much better if you can replace the filter.
  3. Sanitize the tub well using the proper cleaning solutions.
  4. Let the tub dry without leaving any cleaning material residues.
  5. Fill the hot tub with water using a hose (to avoid contaminants).
  6. Test your water for the correct chemical balance. Check for pH, alkalinity, and sanitizer levels. You can use test strips for this. Bear in mind that water with a low calcium level in the water does not only cause foaming but can also corrode your spa equipment.
  7. Let the water rest and stay still for 24 hours. Beyond this time, water in your hot tub should clear up.
  8. If the water still has foam, drain and repeat cleansing the tub.
  9. Refill the hot tub with water again.
  10. Redo the test and, once you get good results, you can already resume using the hot tub.

In an ideal scenario, the above steps may work. However, if all else fails, it will be wise to seek the help of hot tub or spa maintenance experts as they will know best how to fix the problem. Please remember that low calcium levels in the waters or water hardness can also cause foaming that can damage your hot tub and spa equipment. Some chemical imbalances can also happen if you use cheap chemicals. To ensure that your water has the correct pH, calcium, alkaline, and sanitizer level, you may do a test at least weekly. Well-balanced water can give you a most satisfying hot tub experience sans the foam.

How to prevent foamy hot tub water?

The number one rule will always be regular draining, cleaning, and sanitizing your hot tub. Drain, clean, and sanitize your hot tub regularly. You can also shock your spa after any hot tub party. You can also do this routinely at least once a week. Remember that as more people dip in the hot tub, the chance that the tub will have foamy water in the succeeding use can increase.

Cleanse and rinse yourself before soaking in the hot tub. A quick shower will do the trick to remove all the dirt, sweat, lotions, deodorants, colognes, perfumes, oils on your hair and skin before dipping in the tub. Bathing suits must also be cleaned and rinsed in the shower before jumping into the tub to remove detergent residues.

Choose your chemical brands wisely. Cheaper chemical brands can do your hot tub more harm than good. There are several excellent products in the market that you can buy from reputable sources. Better yet, you can even do some research online before the purchase. You may also seek the assistance of your trusted spa stores for any advice.

If your hot tub is covered, you can open the cover regularly – this can also prevent foamy hot tub water as it allows the water to breathe. Even your hot tub needs some fresh air and oxygen at least once a week.

Are there other ways to prevent hot tub foam?

Another natural way of defoaming your hot tub will be using vinegar. Just follow the 1:10 ratio mix, let it stay for a couple of hours, and then drain. You can also use two parts vinegar and one part baking soda and mix it with nine parts of water. You can then pour the mixture into your hot tub, leave it there for 30 minutes and drain. Other people are opting to use these natural methods as they can be environment friendly and may lessen the presence of more harmful chemicals in your hot tub.

Have you heard about giving your tub some spa shock treatment?  It can be a treatment that can help you get rid of the foam. You can do this by shocking the water with sanitizer. Chlorine is a popular and recommended type of sanitizer for this job. First, switch and run the water jets on a high setting. It is advisable to leave the tub’s cover half open to let the gases evaporate. Then, you may rinse and drain and proceed with cleaning and sanitizing the tub.

If you are too busy and do not have plenty of time to spare, there are foam removers that you can buy from your local stores, or you can also order them online. Most of the time, these defoamers can resolve the foam issue quickly, and the results can last for up to 24 hours.


Having foam in your hot tub can be utterly frustrating. But it is something that you really cannot avoid from happening. The foam in your hot tub may only tell you that the spa is being used and enjoyed, and you need to look into some items that you may have missed in caring for them. The task of removing the foam and preventing them from resurfacing again can be a bit challenging but, there are many ways to prevent foam from forming and showing up in your hot tub or spa. Just make sure to observe the simple steps listed above and diligently have your hot tub regularly cleaned at least once a week. Just like any other home equipment, your spa also needs some tender loving care so you can enjoy them better for a longer time. At the end of it all, once you get those foam out of the way, you can still have fun and enjoy soaking in your hot tub!

The bubbles don’t harm you or the hot tub at any time and are all ubiquitous household items, many of which can be found in our people at any given time, so it makes sense only to see bubbles in the hot tub.

Another potential cause of foaming is the accumulation of bacteria, also known as biofilms. If the product is not thoroughly rinsed after cleaning the filter, it also can cause foaming.

If you don’t regularly flush the filter or use monthly deep cleaning like Filter Restore to clean the filter, the filter can be a source of foaming if you have enough surfactants in your water to cause foaming. If the water is almost ready to be replaced and starts to foam, the best thing to do is flush and clean the hot tub.

A defoamer for hot tub water will help combat foam for a while, but it’s best to be as clean as possible before entering the tub. Then, balance the water chemistry and change the water every three months to remove the foam. Scheduled water and filter changes and weekly water chemistry monitoring are the best way to avoid foam in the hot tub.

Because a hot tub works differently than a bathtub, foam in spa water indicates a problem and can cause more problems if foam gets into pipes and pumps. Foam in a spa is due to the water being “full” or “old,” and activating spa jets when water is such causes foam to appear on the water’s surface. Typically, foam in a hot tub can be caused by excessive lotions, dirt, perfume and deodorants that people have gotten into the water.

Low calcium levels (water hardness) in the spa can reduce the surface tension of the spa water and lead to excessive foaming. In addition, low calcium levels (water hardness) can reduce the surface tension of the spa water and lead to excessive foaming of the water. 

The oils in water can come from body care products such as lotions, sunscreens and deodorants, hair care products like conditioner and mousse can also be problematic; too much or the wrong amount of chemicals in the water can also contribute to causing foam in your spa.

When these impurities are in the water, they stick to the bubbles, making the water too thick and foaming if it is not treated further (usually during the day ). Therefore, another tip that we recommend is to purchase a chemical defoamer, as this is ideal if you are short on time and cannot purify the water.

Check the level of chemicals and disinfectants in your water if necessary and add more if required to restore the correct level. Before taking any corrective action, test your water to see your pH, alkalinity, and disinfectant and check your total dissolved solids (TDS) – these are surfactants.

If the water is at the wrong pH and is too acidic or alkaline, it can cause many problems, including excessive foaming. Cloudy or foamy water often indicates an incorrect chemical balance in thermal water. A ring around the tub around the spa can also result from poor water balance. Cloudy, frothy water occurs when soaps, shampoos and lotions fly off people’s skin or swimwear when they take a bath.

To rid your water of these unwanted guests, shock your spa every big party and regularly at least once a week. Pouring more chlorine into the spa will help destroy everything that makes your spa frothy (no matter if the chemical levels are balanced, but the whirlpool remains frothy).

Take your filters, wash them thoroughly, or soak in a filter cleaner overnight. Swimsuit residue from laundry detergent can form a foamy mass, so make sure your swimwear is clean and rinsed with fresh water before getting into it.

All you need at a Sundance Spa to keep your water clean is a small amount of powder disinfectant and a minimum amount of chlorine-free spa shock. If you regularly do your hot tub chemistry, spa water is thoroughly mixed with disinfectant chemicals and calcium to neutralize surfactants and prevent bubbles from forming. However, the first two methods involve maintaining the water, and you will still feel foam and cloudy water build up in the hot tub.

Also Read:

Hot Tub Chemicals Guide

How to Properly Clean a Hot Tub


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