What Causes Foam in a Spa or Hot Tub?

What Causes Foam in a Spa or Hot Tub?

If you’ve ever turned on your jets and suddenly seen a layer of thick, fluffy bubbles take over the water, you’re not alone. Foamy hot tub water is one of the most common issues spa owners run into, and the good news is that it almost always comes from simple, fixable causes.

Why Foam Forms in Hot Tubs

Foam appears when products and contaminants mix with warm, circulating water. As soon as the jets run, they whip everything into bubbles, similar to shaking up a soapy bottle.

Some of the most common contributors include:

  • Lotions and body oils

  • Hair products or deodorants

  • Laundry detergents and fabric softeners on swimsuits

  • Leftover cosmetics or perfumes

Even small amounts can create a surprising amount of foam once they circulate through a heated spa.

How Water Chemistry Makes Foam Worse

When your water chemistry is off, your sanitizer can’t break down buildup effectively. That means oils and residues linger longer and start forming a film on the surface.

Keep an eye on:

  • pH: Ideally between 7.2 and 7.8

  • Sanitizer level: In the recommended range for your system (chlorine, bromine, or alternative systems)

If these drift too far out of range, contaminants build up faster and foam becomes more noticeable.

Quick Ways to Get Rid of Foam

If you need a fast fix before guests arrive or you just want clear water again, a spa defoamer can help. Add a small amount, run the jets, and the bubbles usually disappear within minutes.

Just remember:
Defoamer is a temporary solution, not a cure.

For a longer lasting fix, try:

  • Cleaning or replacing your filters

  • Shocking the water

  • Balancing pH and sanitizer

  • Draining and refilling the spa if the water is overdue for a full change

How to Prevent Foam from Coming Back

Prevention is much easier than cleanup. A few simple habits keep your hot tub water clean and foam free:

  • Rinse off before getting in

  • Avoid using fabric softeners on swimwear

  • Limit lotions, cosmetics, and hair products before soaking

  • Stick to a regular water care routine

  • Change spa water every few months depending on use

Small steps make a big difference, and your water will stay cleaner and clearer much longer.

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.