Troubleshooting foamy hot tub water: Causes and solutions

Nothing compares to the relaxation of soaking in an outdoor hot tub — especially when it’s in your backyard. So, it can be surprising to lift the cover and find foamy water instead. 

While foam in hot tub water can be frustrating, it’s not a cause for alarm and is often easy to prevent. 

By understanding what leads to foamy water — and taking a few simple steps to keep it in check — you can ensure your hot tub stays inviting and ready for your next soak.

What causes foamy hot tub water?

Foamy hot tub water might catch you off guard, but it’s usually a sign that something has built up in the water over time. From leftover body lotions to changes in water chemistry, a few common culprits can introduce foam. 

Body care and hair care products

Lotions, deodorants, sunscreen, and other skin care products can easily transfer from your skin into the hot tub water, especially when you're soaking in the heat. The oils and chemicals in these products, along with hair care products like conditioner and styling gel, can contribute to foam buildup. When these products are used, the heat from the water and the movement of the jets can disperse them throughout the tub, increasing the chances of foam forming.

Soap residues

Detergents from swimsuits or body washes that haven’t been thoroughly rinsed off can contribute to foam in your hot tub. When washing your swimsuit or showering before a soak, any leftover soap, detergent, or fabric softener can transfer into the water. The warm water and jet movement can cause these residues to bubble up, leading to suds on the surface.

Low calcium hardness

Calcium hardness refers to the amount of dissolved calcium in your hot tub water. When calcium levels are too low, the water becomes more likely to foam because it can’t properly balance out other minerals and contaminants. In addition, low calcium hardness can make the water softer, which allows soap, oils, and other debris to create foam more easily. 

Beverages or food

Enjoying a drink or even a snack while soaking in your hot tub can be a great way to relax, but spills or crumbs can contribute to foam in the water. When drinks or food crumbs fall in, the sugars and oils from these items can mix with the water and create bubbles. It’s easy to overlook, but even small amounts of spilled beverages or snacks can lead to foam buildup. 

How to get rid of foam in your hot tub

If you’ve noticed foam building up in your hot tub, it’s important to address it quickly to maintain clean and inviting water. Fortunately, getting rid of foam is straightforward. With the right approach, you can have your hot tub back to its crystal-clear state in no time.

Use an anti-foam product

A quick fix is to use an antifoam product designed for spa water. This type of product works by breaking down foam and preventing algae growth, keeping the water clean and clear. However, while anti-foam is helpful, it’s best used as a temporary solution.

Skim the surface

After applying an anti-foam product, you can manually remove any leftover foam on the surface. Use a pool skimmer or a net to scoop away bubbles, especially if there’s a lot of foam. Skimming is a simple but effective step to make your water look clean right away.

Test and adjust chemical levels

Foam in hot tub water can often indicate imbalanced water chemistry. Regularly test your water to ensure that your pH, alkalinity, and calcium hardness levels are in the correct ranges:

Calcium hardness: Low calcium levels make it easier for foam to develop. Ideal calcium hardness for hot tubs is between 150 and 250 ppm (parts per million).

pH and alkalinity: Balanced pH and alkalinity help keep the water stable, reducing the chance of foamy buildup. Aim for a pH of 7.4 to 7.6 and alkalinity of 80 to 120 ppm.

Clean and rinse your filter

Hot tub filters are essential for maintaining clear, foam-free water. They work by trapping oils, hair products, lotions, and other debris that can contribute to foam buildup. Over time, these contaminants can clog the filter, reducing its effectiveness and allowing foam to form more easily. 

Instinct Spas recommends rinsing your filters once a week and using a filter cleaner once a month. In particular, a filter cleaner helps break down oils and stubborn particles that might be stuck in the filter’s fibers, keeping your water cleaner and reducing the chances of foam.

Drain and refill if needed

If the foam doesn’t clear up after a few days, it might be time to do a complete water change. Draining and refilling your hot tub is a reliable and efficient way to reset your water, especially when trying to balance chemicals feels like an uphill battle. Sometimes, repeated attempts to adjust the water chemistry can take more time and chemicals than simply starting fresh. Before refilling, take the time to scrub the shell and remove any biofilm or residue that could cause foam to return.

Preventing foam in your hot tub water

No hot tub owner wants to deal with foamy water. It can be frustrating and time-consuming to clean up once it’s there. The good news is, with a little bit of care, you can prevent foam from ever becoming an issue.

Rinse off before using your hot tub

Taking a quick shower before entering your hot tub rinses off oils, lotions, and other products that can cause foam. This step is particularly helpful if you’ve applied sunscreen, lotion, or hair products.

Wash and rinse your swimsuit

Detergent residue on swimsuits is a common cause of foam in hot tubs. After washing, thoroughly rinse your swimsuit to remove any soap, then let it air dry. Consider designating a swimsuit specifically for hot tub use to minimize detergent buildup.

Limit food and drinks

Avoid bringing beverages, food, or snacks into the hot tub area to prevent spills that might contribute to foamy water. While it’s relaxing to sip a drink in the hot tub, even a few drops can promote foam formation.

Tie up long hair

Long hair can release oils and products into the water, so consider tying it up or wearing a swim cap to reduce contact with the water. 

Keep the cover on when not in use

One of the simplest yet most effective ways to prevent foam in your hot tub is to keep the cover on when it's not in use. When the cover is left off, debris such as leaves, dust, and airborne contaminants can easily enter the water. This introduces additional oils, dirt, and organic material that can contribute to foam buildup. A cover also helps to keep your hot tub water clean by minimizing the need for frequent chemical adjustments, saving you time and effort. 

Regular hot tub maintenance tips

Proper maintenance is key to ensuring your hot tub stays in top shape and preventing issues like foamy water from becoming a recurring problem. By staying on top of routine care, you can keep the water clean, balanced, and inviting, making each soak more enjoyable. And regular maintenance doesn’t just address foam; it helps extend the lifespan of your hot tub, reduces the need for costly repairs, and keeps the water chemistry balanced.

Test water regularly: Use test strips or a water testing kit at least once a week to check pH, alkalinity, and calcium levels.

Shock your hot tub: Shocking involves adding a non-chlorine oxidizer to break down contaminants. Shock your hot tub water every one to two weeks, especially after heavy use.

Check calcium hardness levels monthly: Use a calcium increaser if your water’s calcium hardness is low. This helps to maintain balanced water chemistry.

Replace water as needed: Changing your hot tub water every four to six months can help a clean, foam-free soak each time you use it.

Why keeping your hot tub clean matters

Foamy water may seem like a minor inconvenience, but it can affect the lifespan of your hot tub. Oils, soaps, and contaminants that lead to foam can also clog your filters, affect your heater’s performance, and reduce water circulation. By addressing foamy water quickly, you’re also protecting your investment.

Keeping your hot tub water clean and foam-free is essential for enjoying a high-quality, comfortable soak. With a little preventative care and regular maintenance, you can avoid foamy water and enjoy your hot tub to its fullest.