Does your hot tub look like a giant bubble bath? But not in a good way?
Then it’s time to learn what’s causing that foam, how to get rid of it and prevent it from coming back.
In this article we’ll dive into:
- Causes of Foamy Hot Tub Water – Learn what creates foam in your hot tub, including surfactants from oils, lotions, detergents and even water chemistry issues
- Foamy Water Solutions – Step-by-step solutions for removing existing foam, from balancing your water to shocking and cleaning the hot tub
- 5 Steps to Prevent Foamy Hot Tub Water – Proven prevention methods to keep foam from forming again, including draining, shocking and rinsing routines
Foam in the hot tub happens, but FROG®, the water care expert, is here to help!
Why is My Hot Tub Water Foamy?
Hot tub foam forms when water, air and surfactants mix together. Surfactants are compounds that reduce the surface tension of water, making it easier for bubbles to form and persist.
As your hot tub jets agitate the water, air becomes trapped within it. If surfactants are present, they create a thin film around these air pockets, preventing the bubbles from popping right away. The more surfactants in the water, the more stable the bubbles become.
As these bubbles accumulate and cluster together on the surface, they create the foamy water commonly seen in hot tubs.
What causes surfactant build-up?
You may be surprised. Some common things cause surfactant build-up and some you may not even know about. Once you know, you can manage them:
Oils and Lotions
Oils and lotions in the water are the most common cause of foamy hot tub water. Body oils, deodorant, beauty products and body lotion can add a variety of surfactants to the water.
It’s the build-up over time that causes foam. And if the build-up isn’t treated, the surfactants these products add to the water lead to more and more foam.
Detergents and Soap
Detergent and soap residue on your bathing suits and skin inevitably get into your hot tub water when you get into your hot tub. These residues can increase surfactants, and as a result, foam.
Biofilm
Biofilm is a slimy and sticky microbial colony made up of different types of microorganisms including bacteria and algae.
These microbial growths attach themselves to hot tub surfaces. Biofilm develops when your hot tub water is not properly treated or maintained.
Biofilm can lead to foamy water because the bacteria within it produces surfactants as a byproduct of their metabolic processes.
Poor Water Balance
Poor water balance alone won’t cause foamy water. But poor water balance, especially low Total Hardness (also called calcium hardness), lowers the surface tension of water in the same way that surfactants do. When the water’s surface tension is lower, it is easier for it to combine with air, causing foam.
How to Clear Up Foamy Hot Tub Water
Now that you know what causes foamy hot tub water, here’s how to solve it:
1. Balance Your Hot Tub Water
Even when it’s obvious that you have foamy hot tub water, it’s always best to start with balancing your water. Then you’ll know what needs adjusting.
Every time you balance your water, check these levels and correct as needed in this order:
Want more details on water balancing? Download the FROG Water Balancing Guide for Hot Tubs here.
2. Shock the Hot Tub
If balancing the water didn’t get rid of the foam, the next step is to shock your hot tub water.
Hot tub shock oxidizes your hot tub’s water and reactivates your hot tub’s sanitizer. This oxidization helps break down surfactants and ultimately gets rid of foam.
FROG Maintain® is a non-chlorine shock that works in 15 minutes. It comes in a single dose cut-and-pour packet, so there’s no measuring and no mess.
Unlike many shock treatments, FROG Maintain contains no cyanuric acid (CYA). While CYA helps protect chlorine from sunlight in pools, it isn’t needed in hot tubs and can build-up over time, making chlorine less effective.
3. Remove Build-up of Oils, Lotions, Detergents and Soap
If water balancing and shocking the water didn’t get rid of the foam, it’s time to remove any build-up from products that bathers have introduced to the water.
How? Add a scum absorber to the water! You’ll find numerous types of scum absorbers from sponges in fun shapes to scum balls. Check them out at your local retailer.
Once you put a scum absorber into the hot tub water, it will take a couple of days to fully absorb the scum.
However, you can speed up the process by adding multiple scum absorbers to the water. The foam should now recede unless biofilm is the cause.
4. Biofilm? Drain the Hot Tub
If absorbing the scum didn’t solve the problem, it is most likely that the hot tub foam is due to biofilm build-up.
The only way to get rid of biofilm build-up is to drain your hot tub and purge it to clean the filter, surfaces and pipes.
Before you drain your hot tub, consider using a spa purge product. Purging helps remove hidden biofilm, oils and other build-up from inside the plumbing that draining alone can’t reach. Starting with clean plumbing makes it easier to maintain fresh, clean water after you refill. Learn more in our guide to purging your hot tub.
5. Rinse it Out
Thoroughly rinse the hot tub out to ensure all the biofilm is gone – otherwise foam will return. Then, it’s time to refill the tub.
After refilling, balance the water. Once water is balanced, add your hot tub sanitizer.
Water Care Expert Tip: Any type of defoamer or “anti-foam” product is only a short-term fix; it will remove the foam from the water temporarily. If you use an anti-foam product but don’t treat the water fully, the foam will return once the chemical has been used up. Foam is stubborn and is best treated by the five steps outlined above!
And now, here’s 5 steps to prevent foam in your hot tub.
5 Steps to Prevent Foamy Hot Tub Water
1. Drain and Refill Your Hot Tub Regularly
Since foamy water is typically caused by build-up, it’s best to drain, purge and refill your hot tub water regularly. You’ll find a lot of different recommendations on how often to drain your hot tub water, typically anytime from 2 to 3 months.
However, those who use FROG® products can usually increase the time between draining as long as they replace their FROG Mineral Cartridge every 4 months.
Note: Your FROG Mineral Cartridge must be replaced every time you drain and refill your hot tub.
When you drain and refill your hot tub, consider it a refresh as it will get rid of dissolved solids that have accumulated in the water from hot tub use.
Once you’ve drained, purged and refilled your hot tub, be sure to balance the water before adding your sanitizer. Balancing the water is one of the key parts to keeping the water clean, clear and ready when you are!
2. Use a Non-Chlorine Shock Weekly
Use a chlorine-free shock weekly to prevent foamy hot tub water. Shocking the water helps break down oils and lotions or soap and detergent. If you use your hot tub frequently, more than 3 times a week, it’s a great idea to get on a consistent shocking schedule.
We recommend using FROG Maintain® – one dose in an easy-to-pour pouch. Non-chlorine shock also means you get clean water without any additional cyanuric acid.
3. Routinely Clean Your Filter
Clean the hot tub filter at least monthly. There’s an array of products to choose from, including those to soak the filter in overnight or that you can hose off the next day. These cleaners remove all dirt, grease, soap and oil build-up from the filter cartridge.
Another tip: Have an alternate clean filter cartridge ready to use while the “dirty” one is soaking.
This cycle not only helps you avoid hot tub problems, but it also helps extend your filter cartridge’s life. Avoiding trouble is better than fixing it!
4. Rinse off Before Taking a Soak
Take a quick shower before you use the hot tub. This helps prevent large amounts of products you may not even realize are on your skin or swimsuit from entering the water and disrupting the chemistry. Your favorite lotion, perfume, deodorant, sweat from the day, pollen, all kinds of “things” can be rinsed off with just plain water – no soap – and kept out of your hot tub water.
5. Have a Dedicated Swimsuit for Hot Tub Time
Bathing suits that have been washed with typical laundry are filled with detergent. Yes, even if you rinse them, soap residue remains. We recommend you choose a swimsuit that is not washed in a washing machine. Only rinse your dedicated suit with plain water and let it dry between uses.
The Foam Finale
Now you know the various causes of foamy water, including the presence of oils, lotions, detergents, soap residues and biofilm. Most importantly, you know how to address that stubborn foamy water.
Implement preventive strategies and follow a consistent water care routine. Then you can enjoy a crystal-clear and foam-free hot tub experience. Happy hot tubbing!
