Posted by Do you ever open your spa cover and find the tub full of foamy water? This is a common hot tub problem and leaves many people wondering, what causes hot tub foam?
Below, I’ll explain the causes of excessive hot tub bubbles and how to easily fix this problem for good!
There are three main causes of hot tub foam:
Believe it or not, foamy water can be caused by soap residue in your swim suit, as well as fabric softener, body lotion, hair products, skin oil and makeup.
Using a scum digester, such as ecoTUB Scum Buster will remedy foamy water caused by soap residues and beauty products. You can also help prevent foam in the hot tub by using an oxidizing shock after each use and a floating oil absorber, such as a Zorbo.
Low calcium levels (aside from being damaging to equipment) can also decrease the surface tension in the water and allow for excessive sudsing.
To prevent this issue, use Hardness test strips once a week to check and maintain the calcium hardness level in your hot tub. If low, use Calcium Hardness Booster.
Imbalanced water can cause all sorts of issues, from green, to stinky, to even foamy hot tub water.
Prevent foam due to high pH by using pH & Alkalinity Decreaser. Use Alkalinity Up pH & TA Increaser for raising low pH. Test your water once a week to maintain a healthy hot tub.
Based on the cause of your hot tub foam, here are some helpful products:
· Alkalinity Up pH & TA Increaser
· Foam Free Water Defoamer for Spas
Have questions about water chemistry? Post a comment below and our hot tub experts will answer!
Hot Tub Blog | SpaDepot.com 
I really want to get a hot tub for my backyard. I think that it would be fun to sit in during the summer. I know that my wife would love one as well. I have never purchased a hot tub before, so I am going to make sure to do a lot of research before buying one. I can’t wait until I have a hot tub in my backyard.
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That’s really interesting! Wouldn’t have thought the beauty products would do that!
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Last night, I went to get into my hot tub, and I found something very similar to this. It wasn’t this extreme, but it was pretty bad. There was about an inch of foam. I had never had that issue before, so I can’t figure out what it was. I had no idea that make up, and other beauty products would cause foam like this.
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Hi Lacey,
Thank you for posting.
Yeah, hot tub foam can suddenly occur and be quite a surprise when you go to get in.
Have you tested your pH, alkalinity and hardness yet?
Thanks,
Kaisa
The Spa Depot
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Can we add kids to the list? I had my nephews pouring bubble bath in my hot tub because they thought it would be fun. What a mess! lol
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Bet it WAS fun, though! LOL
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My hot tube has white flakes floating on the water when I turn the jets on high and water get foam.
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My hot tube has white flakes floating in the water and foam up when I turn on the jets on high jbranco54@yahoo.com
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Hi Joe,
Thanks for posting. White flakes are usually caused by calcium build-up in the plumbing. Buildup in your spa plumbing can also lead to a host of problems such as hot tub foam and cloudy water.
I recommend using a Spa System Flush: http://www.spadepot.com/shop/Spa-System-Flush-16-oz-P436C57.aspx
To prevent this from happening in the future, be sure to test and balance your pH, Alkalinity and hardness level once a week.
I hope this helps. Please let me know if you have any additional questions.
Thank you,
Kaisa
SpaDepot.com
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My hot tub is cloudy ,using clean water blue system chemicals,ph and alk are in req balance range and copper showing grey on test strips and shock after each use as called out. any solutions.
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Hi Carl,
I’m happy to help. To determine the cause, I just have a few questions:
How old is the water?
How old is the hot tub filter?
Are you using Oxy Spa routinely?
Please let me know.
Thank you,
Kaisa
SpaDepot.com
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My gym jacuzzi always has foam which I can smell urine. How can I make them correct this without getting banned from membership?
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Hi Avis,
Thanks for your post. You could try sending an anonymous letter explaining your concerns. I would strongly recommend not using this hot tub. An under-sanitized public hot tub can lead to serious illness.
If the gym does not take immediate corrective action, I would contact your state health department with your concerns.
Please let me know if you have any additional questions.
Thank you,
Kaisa
SpaDepot.com
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I will definitely try these products you’ve listed. Didn’t have slightest clue that beauty products could cause foam. Thanks for your insights!
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My hot tub foams up and has bright kinda aqua green in it. It will leave a bright green scum around the hot tub. It only does this when we use the jets with air going through them. We have a Clearwater Belize spa.
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Hi David,
Have you flushed your plumbing recently? We recommend using Spa System Flush (http://www.spadepot.com/shop/Spa-System-Flush-16-oz-P436C57.aspx) to super-clean the inside of your hot tub plumbing. It will flush grime, oily residue and heater scale deposits that may be hiding, even if your jetted tub is well maintained.
To use: remove filter, add half a bottle (8 oz.), run pumps and jets for a few minutes (or overnight if possible) then drain away the gunk with the old water. And that’s it!
Thanks,
Rosy
SpaDepot.com
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I am using a Nature Stick and a Cense oxygen infused aromatherapy crystals for my hot tub. Is that enough, or do I need to use more stuff?
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Hi Doreen,
Great question! Nature 2 and using an MPS shock (like the Cense product) after each use is pretty good at keeping the spa clean. You’ll still need to use pH adjusting products occasionally, of course.
However, shocking with dichlor chlorine on initial fill and when occasional problems arise is a good idea. Many people use a small dose of dichlor in their weekly routine to avoid cloudy water. Chlorine doesn’t stick around in the water too long, so you don’t need to worry about soaking in chemicals.
Thanks,
Sarah
SpaDepot.com
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Hi. We drained, vacuumed out the jet ports and completely washed our hot tub yesterday. Friday afternoon, I put a drain prep in the water to clean the plumbing. After filling with oir local water supply, our alkalinity is 350ppm, pH is 8.2+ and zero bromine. I added 200ml liquid acid, 70 gm bromine booster, 120 gm shock and 26ml clarifier. I tested and added an additional 200ml acid late last night after a retest showed the alkalinity at 290ppm. This morning the readings are alkalinity at 230ppm, bromine 1.0 and pH at 8.2+ and we have foam on the water when the pumps are started. I added another 300 ml liquid acid this morning. But what I am struggling with is the foam. Why is this fresh water foaming so much?
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Hi Ed,
Thank you for your question and I really appreciate the details you have provided! The only thing I don’t see in there is calcium (hardness), have you tested the water’s hardness?
Thanks,
Sarah
SpaDepot.com
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Yes, I forgot that detail. Hardness was tested at 250 ppm. And I should also mention we use liquid reagents, not test strips or digital meters.
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Hi Ed,
That’s great to hear that your hardness is in balance, that means you don’t have a more difficult issue on your hands. The foaming is most likely caused by the extremely alkaline water reacting with the acid you are adding, not unlike a baking soda volcano from grade school science class.
Keep adding acid at 12 hr intervals, like you have been doing. Sometimes it takes a surprising amount of acid to bring the pH down. If the acid you are using is a pH Decreaser Liquid type product, then it may even take a few bottles. A buffered muriatic acid like Acid Magic could help you in the future with bringing the pH down significantly.
As for the Total Alkalinity, you can lower that by turning on your jets! Aeration is a great way to get TA down once your pH is in balance.
Let me know if there are any issues or you have any questions.
Thanks,
Sarah
SpaDepot.com
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Hi Sarah. Thanks for your replies. The acid we use is a buffered muriatic acid named Acid Enhance purchased from a hot tub store in my area. This is the 2nd fill we’ve used it with but the last one didn’t foam like it did this time. However, the alkalinity in our water started at 240 ppm, also unlike this time at 350. Since my original post, we added another 150 ml acid and this morning had respectable numbers at 80 alkalinity, 3.5 bromine and 7.6 pH. I will now turn the air OFF to the jets in hopes of keeping it balanced for a period of time. I haven’t run the pumps yet to see if the foam has subsided, bit I will let you know when I check that.
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Hi Sarah. The water has been nicely balanced since Monday. The alkalinity is 60, pH at 7.6 and bromine at 3.5. We’ve always had an issue with lower alkalinity readings when the pH is in a good range, so this is good for us. We use the Langlier Index to ensure oure water quality. However, that pure white foam is still forming on the water when the jets are started. Any rhoughts?
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Hi there, We usually have foamy hot tub water in our hot tub. It has been manufactured in 2014 and we changed it every 2 months. If you have an answer to this problem, please tell me!
Sincerely,
S.F.
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Hi Shan,
The foam could be caused from low calcium hardness, or the pH and alkalinity being out of balance. If you’ve checked those and they’re in balance, you could try using defoamer or our Scum Buster. Those products do a great job keeping the foam away. You could also try using Spa System Flush (MT1028). You run that through the system right before draining, and if there is anything in your piping that is helping cause the foam, that will get rid of it. I hope this helps, and please let me know if you have any other questions.
Thanks,
Mark
SpaDepot.com
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When my spa is cloudy and I add a clarifier and turn my jets on high, I get a green slime in the foam. Any suggestions?
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Hi Colleen,
If you are seeing this green slime only when the jets are on high, I would suggest flushing your system with Spa System Flush (https://www.spadepot.com/Spa-System-Flush-16oz-P817) then draining and refilling your spa with clean water. You could have some hidden bacteria or other microoganisms in the plumbing and jets that would be dislodged with the Flushing.
Also, be sure to monitor and balance your spa water since low levels of pH and sanitizer can cause shades of green water.
Let us know if you have any other questions!
Thanks,
Rosy
SpaDepot.com
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Hi,yes my hot tub is foams when I turn my jets on,I’ve checked with my sticks, everything seems to be fine,could it be the filters need to be changed? When I cleaned my hot tub this summer the water that comes out from for your neck 4little holes it’s not pouring out like it did before,there is one that hardly comes out,I hope u can help thanks
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Hi Kelly,
If you’re noticing a reduction in jet pressure, I’d recommend removing the filters and seeing if pressure is restored. If it is, then you know you should replace the filters. As a general rule of thumb, we recommend rinsing out filters the weekly with a garden hose, deep cleaning them with filter cleaner at each water change, and replacing them annually. Regarding the foam, high contaminates and/or soap residues, buildups in spa plumbing system, or low calcium water hardness are the usual culprits. If you have not changed your water since the summer, I would recommend the following course of action:
1. Use a bottle of Spa System Flush in the tub
2. Drain the water
3. Clean the shell of the tub with Clean All
4. Clean or replace the filter (depending on the age and condition of the filter)
5. Refill the tub, paying special attention to calcium hardness. You’ll want it in the 150-300 ppm range
If you’d like to chat about it, give us a call at 800-823-3638, 6am-5pm Pacific, Monday through Friday and we’d be happy to walk through getting the water foam free!
Thanks,
Brian
spadepot.com
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My family will be vacationing at a rented cabin over New Year’s. We stayed here last year and the hot tub foamed up to the point it kind of ruined the experience. We would like to know if there is something we could do to minimize or prevent the foam for our long weekend without spending a lot of money maintaining a hot tub that should already be maintained. I’ve read all of your excellent advice but don’t feel I should be responsible for testing the water. I just want to be able to make our time stress free. Considering some Scum Buster and maybe some sodium dichlor. Any advice would be greatly appreciated.
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Hi Brian,
The issue you’re describing is actually quite common unfortunately. I would strongly recommend getting in touch with the property manager and asking if they can do a drain and refill on the tub before your stay. If that’s not possible, there are a couple of things you can do yourself to help with water quality. First, shock the water with Dichlor and rinse out the filter. Then, after each use, shock with Oxy Spa non chlorine shock per the instructions on the bottle. That will go a long way towards keeping the water safe and foam free.
Thanks,
Brian
Spadepot.com
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Why is there foam when the hot tub isn’t being used ?
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Hi James,
There could be lots of reasons, but the most common is not shocking the water frequently enough. Even if you’re not using the tub, the water should still be sanitized and shocked. If you’d like to go over some of the more specific reasons your tub may be foaming, give our water chemistry department a call at 800-823-3638 and we’ll be able to get you fixed up in no time.
Thanks,
Brian
SpaDepot.com
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I have a hot tub that usually stays clean and foam free. We occasionally have a guest that will get in and without fail, after a few minutes, the water will get foamy with a grey looking scum. After his departure, I always have a ring so the tub must be emptied, cleaned and the filter cleaned or changed. Is this coincidence or something about his body? It is just a little gross!!
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Hi Laurie,
When you consider what causes the foam, you’re right, it’s gross. I know it’s hard/uncomfortable asking everyone to shower before using the tub, but it will go a long way to ensuring lasting water quality. Remember as well, after a high bather load or sanitizer demand, shock the water with a good oxidizer such as OxySpa – you’ll be amazed at the good it will do.
Thanks,
Brian
SpaDepot.com
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my foam goes crazy when i add spa plus to bring the PH up, so then i ad the foam decreaser and the foam gets better but it seems to lower the PH again. Am i losing my mind
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Hi John,
You’re definitely not losing your mind. If you’re using pH increaser, you’re actually bringing up the TA a little as well. Try using Easy pH instead. It will raise only the pH, and leave TA alone. Give us a call at 800-823-3638 and we can make sure you get everything you need for a foam free experience.
Thanks,
Brian
SpaDepot.com
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My hot tub is clear as can be whenever we open it up. The only time it foams up is when the jets are running and then as soon as we turn the jets off it clears up. Why is this?
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Hi Lori,
Even if the water is clear, the underlying water quality issues are usually always the same: Organic matter, Low hardness and/or high/low pH. The fact that the foam only presents itself when the jets are on is due to aeration.
Give us a call at 800-823-3638 when you have a moment near the spa and we’ll be happy to troubleshoot and get you back on track.
Thanks,
Brian
SpaDepot.com
800-823-3638
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My hot tub has been turn off due to electrical problems for about 2 mos. it’s fixed now. When I opened the cover the water was crystal clear and cold. I added chlorine to it and the water developed foam. What do I do now?
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Hi David,
Since the water has been sitting for 2 months without circulation, I recommend doing a drain and refill. If that’s not an option, before you do anything, try these 2 things: Clean your filters and adjust your pH, TA and hardness. Once you’ve got those things done, I bet the foaming is reduced dramatically.
Thanks,
Brian
SpaDepot.com
800-823-3638
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I just purchased an inflatable hot tub. The first few days went great. Today, i turned on the jets and it looked like my washing machine overflowed with soap. It finally calmed down, but it was crazy. My pH levels are fine, no makeup, or anything out of the ordinary. I circulate it about 2-3x a day.
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Hi Rebecca,
You didn’t mention if you were shocking the water after each use. So often, this foaming is due to inorganic matter in the water. Shocking breaks down those compounds, reducing or eliminating foaming.
Thanks,
Brian
SpaDepot.com
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Water is sparkling. Consistently adjusting the ph and alk as they daily fluctuate. Have new tub for 10 months now, on 4th filter, have changed water 5 times now. Its fantastic for 4 weeks, then the foam starts. Use foam away and it stops, but it leaves scum type deposits, and you can see the chemical floating on top. We fight this battle for 3 weeks or so, then we flush the jets and drain the tub. We then clean by hand with a small amount of diluted vinegar and lemon solution, rinse it well, and start all over. Thoughts ?
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Hi Dan,
Are you shocking the water after using the tub to break down the oils and contaminants that are causing the foam? Try shocking the water with a good non chlorine shock after each use (or once a week if you aren’t using the spa). Additionally, rinsing the filters weekly and using an oil absorbing device like a Zorbo will greatly reduce foaming.
Thanks,
Brian
SpaDepot.com
800-823-3638
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Wow I did not know that clothes in the hottub could cause that foamy stuff after use. Thank you for sharing. I love findng little nuggets of information.
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