Why is my hot tub foaming?
Short answer
Foam is soap, lotion and body oil whipped up by the jets, and soft water makes it worse. A defoamer knocks it down for a while, but Hot Spring's manual says only a water change removes the soap.
What causes foam in a hot tub?
Soap. It comes off people's skin, out of swimsuits that went through the wash, and from cosmetics, lotions and surface cleaners. The jets beat air into it, and it builds every time the tub runs. Master Spas adds high pH, algae, and low calcium or low sanitizer as things that make foaming worse. Caldera's manual singles out soft water, meaning low calcium hardness.
How do you get rid of hot tub foam?
- Test and balance the water, including calcium.
- Use a little defoamer for a quick fix. Master Spas warns that overuse turns the water cloudy and milky.
- An enzyme product helps break down oils, per Master Spas.
- Drain and refill when it keeps coming back. Defoamers suppress foam but can't remove soap; Hot Spring says no chemical oxidizes soap, though ozone and its salt system can break some down.
How much to add
The product label sets the dose, by your tub's gallons.
Strengths differ between brands of the same chemical, so we don't print amounts. Test, read the label, add a little at a time with the jets running, wait, and test again. Your tub's gallons are in its manual or in our gallons and filter size table.
How do you stop hot tub foam from coming back?
Keep soap out. Bullfrog says rinsing swimsuits and showering without soap before getting in makes the water last longer. When you clean the cover, Hot Spring says to keep its seams closed so cleaning soap doesn't run into the water. Hot Spring puts the water's life at about four months, depending on how much soap goes in. See how often to change hot tub water.
Common questions
Is foam in a hot tub dangerous?
Foam itself is soap and oils, but it signals water that is due for a change. Check sanitizer and pH, and plan a drain and refill if it keeps returning.
Will shock get rid of hot tub foam?
Not reliably. Hot Spring's manual says soap is not oxidized by chemicals added to the spa, so the lasting fix is a water change.
Why does my hot tub foam when the jets are on?
The jets beat air into soap and oils already in the water. Soft water (low calcium) makes it foam more, per Caldera and Master Spas.
Sources
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