Why is my hot tub water foamy?

A little foam that disappears when the jets stop is normal. Foam that stays, or builds into a layer, means the water is carrying something it should not.

Where it comes from

• Detergent in swimwear. A very common cause. A little left in the fabric from the wash is enough.
• Lotion, sunscreen, hair products and makeup.
• Soft water. Water low in calcium foams more easily.
• pH and alkalinity out of range.
• A dirty filter, which leaves more of all this in the water.
• Old water that has collected months of the above.

Keeping it away

• Rinse off before getting in.
• Rinse swimwear in plain water, and keep a set that never goes through the wash with detergent.
• Keep the filter clean and the water tested.

About foam removers

A defoamer makes the foam go down, and it has its place before guests arrive. It does not take anything out of the water, so the foam comes back. If it keeps coming back, the water needs changing.

This is general guidance. Your hot tub's owner's manual comes first, and so do the instructions on your products.

Sources: Bath & Spa Parts: Why is my hot tub foaming?; Platinum Spas: Hot tub foam.