How to deal with foamy hot tub water is a matter of preventing contaminants and surfactants accumulating in your spa water. Hot tub foam can also be caused by unbalanced water chemistry or low calcium hardness.
Normally the best way to get rid of foam in a hot tub is to drain, clean and refill the hot tub with fresh water. As hot tubs contain a very small volume of water the tub must emptied, cleaned and refilled every three months. Maintaining balanced water chemistry, adequate sanitation and clean filters will prevent the problem recurring.
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What Causes Foamy Hot Tub Water
Normally, the water in a hot tub is clean and crystal clear with no foam. When the pump operates there will be bubbles that form on the surface which burst. When the pump is off there should be no bubbles or foam. If there is soapy foam residue you have a foam problem.
There are a number of reasons why foam forms in hot tubs and spa pools. The number one reason is a build-up of contaminants and surfactants in the water.
Hot tub foam can also be caused by unbalanced water chemistry or low calcium hardness in the water.
If you are having problems with foam forming in the hot tub water you need to identify the issue to eliminate and prevent it recurring.
1. Detergent
Obviously, if some sort of detergent has found its way into your hot tub this will cause foamy water.
The detergent may not have been intentionally added. It may be soap residue on your skin or haircare product residue in your hair that has washed off into the spa. Someone may have rubbed body lotion on their skin or spilled some food or drink into the spa.
It may not matter how it got there but unfortunately the filter is not going to remove it. The only way to remove detergent from a hot tub is to drain and replace the water.
2. Surfactants
The word surfactant was created from surface-active agent.
In chemistry, surfactants are compounds that lower the surface tension between a liquid and another liquid, solid or gas.
Surfactants may act as detergents, wetting agents, emulsifiers or foaming agents
All substances added to the pool water increases the total dissolved solids (TDS) in your pool. This includes all the normal pool chemicals such as chlorine, shock, pH reducer, algaecide, etc. and sweat, cosmetics, hairspray, sunscreen, etc. from swimmers. Over time the TDS level will increase and eventually the water will be over saturated with dissolved solids.
Many of these dissolved solids act as surfactants and can cause foaming in the water. Unfortunately, total dissolved solids cannot be chemically treated or filtered from the water.
3. Contaminants
The following are some common contaminants found in spa water that may cause hot tub foam.
- Cosmetics
- Moisturizers
- Sunscreen
- Shampoo
- Conditioner
- Mousse
- Hairspray
- Fake tan lotion
- Perfume or cologne
- Ointment
- Soaps
- Laundry detergent
- Sweat
- Saliva
- Blood
- Urine
- Faecal material
4. Water Hardness
Water hardness is the measure of all the calcium compounds dissolved in the hot tub water.
The recommended level of calcium is 200 – 400 ppm.
Water that is too low in calcium may reduce the surface tension of the water to cause the formation of surface foam in your hot tub.
5. Water Chemistry
Unbalanced water chemistry may cause foamy water.
Usually the culprit is high pH and high alkalinity.
Check the water regularly and adjust if required.
Please read our article on Hot Tub Water Chemistry for further information
How to Prevent Foamy Hot Tub Water
1. Shower before Hot Tub
Most people forget how many pharmaceutical products we have on our skin and in our hair. Products like deodorant, perfume, shampoo, hair conditioner, moisturizers, sunscreen and make-up.
Showering with soap before getting into a hot tub removes all the contaminants and pharmaceutical products from your body.
When body perspiration and pharmaceutical products enter the hot tub water it can result in foamy water. The chemicals, chlorinator and filter will not be able to remove the detergent or soap from the water. The filter element will clog up with soap. The soap will unbalance the water chemistry causing the water to become more contaminated.
Please read our article on Should You Shower Before You Swim?
2. Water Chemistry
Test your hot tub water every week with a test strip to ensure the chemistry is balanced. If not, balance the hot tub water as required.
3. Water Hardness
Soft spa water will cause foam in a hot tub. If your calcium hardness is less than 200ppm add a calcium increaser to the water. Please follow the instructions on the container.
4. Regularly Clean the Hot Tub Filter
Most hot tub filtration units do not have a backwash function like a sand filter for an inground swimming pool. The filter unit has to be opened up and the filter element removed for cleaning.
Many hot tub owners don’t clean the water filter enough. Once the filter element becomes soiled with dirt and other contaminants the pressure within the filter system will increase indicating that it is harder for the pump to push the water through the filter element.
Now is the time to open the filter and manually clean the element. When a hot tub or spa pool is regularly in use the filter will need to be cleaned every two weeks.
Please read our article on How to Clean Your Hot Tub Filter
5. Regularly Open the Hot Tub Cover
When you hot tub is covered 24 hours a day the water is not exposed to the sun and fresh air. This may contribute to the accumulation of surfactants in the water and foamy water.
Regularly open the hot tub cover to expose the water to fresh air and sunlight. Water absorbs oxygen from the atmosphere and UV light kills contaminants in the surface layer of water.
Please be careful that young children cannot access the hot tub while the cover is open.
How to Fix Foamy Hot Tub Water
Once you have foamy hot tub water there are only a few ways to eliminate it from your hot tub. Shocking the tub once a week neutralizes all contaminants in the water that cause foam. Cleaning or replacing the filter cartridge helps to remove the neutralized contaminants from the water.
If the foaming problem continues you can try an anti-foaming spa product but usually these are only a short-term solution that masks the real problem. It’s like spraying a perfume to cover up a bad smell when you need to eliminate the cause of the smell.
However, once the water is saturated with chemicals you don’t have any other option but to drain and refill the water.
1. Shock the Hot Tub
When you frequently use your hot tub shock it once a week.
Shocking increases the chlorine level too high for bathing. Don’t use the hot tub until the chlorine level has dropped back to normal. The chlorine level must be below 5ppm otherwise it will irritate your skin and eyes.
Please follow the instructions on the product for the correct amount of shock for your size hot tub. Be careful to not add too much shock to a hot tub as it will make the water cloudy. A hot tub only has a small volume of water not like a swimming pool.
2. Replace the Filter Cartridge
Hot tub filter suppliers recommend to replace the filter cartridge every 12 to 24 months. However, this is only a recommendation and you need to take into consideration the usage level of your hot tub or spa.
Hot tub filter elements quickly become dirty and require frequent cleaning. However, the more you clean a filter element the more you risk damaging it and you shorten its life span.
Hot tub filter cartridges are relatively inexpensive so it’s not worth trying to make your filter elements last longer. Replace the filter cartridge twice a year.
3. Anti-Foam Products
When shocking the water and replacing the filter cartridge do not solve the foam problem you can try an anti-foam product. These anti-foam products do not resolve the cause of the foam but try to suspend the foam in solution until the water is changed.
I normally don’t recommend de-foaming the water with another chemical product because these products add to the total chemical composition of the water. And chemicals cannot be filtered out of the water. Once the hot tub water is saturated with chemicals you really need to change the water.
4. Change the Water
When a hot tub is used every day by many people the water quickly becomes contaminated with perspiration, skin flakes, body oil and many other organic substances. Adding more chlorine or bromine is the only way to sanitize the water. Eventually the small volume of water in a hot tub becomes too contaminated and saturated with chemicals to sanitize. You need to drain the water and refill the hot tub with fresh water.
Normally, I recommend draining and refilling a hot tub 4 times a year.
Please read our article on How Often Should You Change Your Hot Tub Water
Conclusion
Hot tubs and spa pools are great fun and have many health benefits but you don’t want to be bathing in foamy hot tub water. Cleaning your filter, keeping your water balanced and properly sanitized will help to prevent foam forming in the water. However, hot tub water simply becomes chemically dirty after 3 or more months. No amount of chemical treatment or filtering will fix the problem. Once you have a high level of total dissolved solids in the water the only thing you can do is drain and replace the water.
