Just when you’re ready to sink into the relaxing warmth of your hot tub, you notice something alarming: mildew or mold.
Unfortunately, hot tubs create the perfect environment for fungal growth. Warmth, moisture and limited airflow can allow mildew and mold to develop on covers, pillows, filters and other surfaces.
The good news? With quick action and regular maintenance, you can remove mold and mildew and help prevent them from coming back.
What Is Mildew?
Mildew is a type of fungus that thrives in damp, humid areas with poor ventilation. In a hot tub, it commonly forms:
- Under the hot tub cover
- Along the waterline
- On hot tub pillows
- In folds and seams of vinyl surfaces
Mildew typically appears as a white, gray or slightly yellow coating. While it’s usually less concerning than mold, it can create unpleasant odors, stain surfaces and trigger allergies or respiratory irritation in sensitive individuals.
What Is Mold?
Like mildew, mold is a fungus. However, mold tends to penetrate deeper into porous materials and can spread more aggressively.
Mold comes in many colors, including black, green, gray and brown. It reproduces by releasing microscopic spores that float through the air and settle on damp surfaces, where they can quickly grow and multiply.
In hot tubs, mold is most commonly found on:
- Spa covers
- Pillows and headrests
- Filters
- Waterline surfaces
- Hidden areas beneath the cover
Why You Should Act Fast
The moment you spot mildew or mold, it’s important to address it.
If left untreated:
- Mold and mildew will continue to spread
- Odors may worsen
- Surfaces can become stained or damaged
- Spores may contaminate filters, covers and other porous materials
If You Find Mildew
Clean the affected area with a mild soap or detergent.
Rinse thoroughly.
Dry the surface completely.
Because mildew grows on surface moisture, prompt cleaning and drying are often enough to stop it from spreading.
If You Find Mold
Follow these steps to thoroughly remove mold from your hot tub system:
1. Shock and Purge the Spa
Before draining, shock the hot tub and use a spa purge product like RANA® Pipe and Jet Cleanser to help clean plumbing lines and remove build-up inside the pipes.
2. Drain the Hot Tub
Completely drain the spa to allow access to all surfaces.
3. Clean All Surfaces
Using a mild detergent like RANA® Surface & Cover Cleaner to clean every accessible surface, paying special attention to porous materials where spores may linger.
If using bleach on spa covers or pillows, always consult your owner’s manual first to confirm that bleach is safe for those materials.
4. Let Sunlight Help
Expose the hot tub and cover to direct sunlight whenever possible. UV light can help reduce mold spores naturally.
For spa covers:
- Remove the foam inserts from the vinyl cover
- Clean cover components with mild detergent
- Use a diluted bleach solution only if recommended by the manufacturer
- Allow components to dry thoroughly
- Inspect protective plastic wrapping for tears before reassembling
5. Evaluate Your Cover
Older, waterlogged covers lose insulating value and become more susceptible to mold growth.
If your cover feels heavy, remains damp or shows recurring mold problems, contact your dealer about replacement options.
6. Refill and Rebalance
Once cleaning is complete:
- Refill the hot tub
- Balance water chemistry
- Restore sanitizer levels
- Resume normal maintenance
Preventing Mold and Mildew
The best way to deal with mold is to prevent it from growing in the first place.
Maintain Proper Water Balance
Regularly test and adjust:
- Total Alkalinity
- pH
- Calcium Hardness
Balanced water supports sanitizer effectiveness and helps reduce conditions that encourage growth.
Keep Sanitizer Levels Consistent
Ensure your sanitizer system is functioning properly and maintained according to manufacturer recommendations.
Clean Filters Regularly
Dirty filters can harbor contaminants and reduce water quality.
A monthly cleaning schedule is recommended for most hot tubs.
Use Your Hot Tub Often
Regular use helps release trapped moisture and humidity from beneath the cover.
For outdoor spas, periodic exposure to sunlight can also help reduce mold spores on exterior surfaces.
Purge Plumbing Before Draining
Use a hot tub pipe-cleaning product before each drain and refill cycle, typically every 3 to 4 months.
Clean Surfaces Regularly
Take a few minutes each week, or at minimum once a month, to:
- Wipe down spa surfaces
- Clean and dry pillows
- Inspect the underside of the cover
- Check areas around the waterline
- Protect Covers and Pillows
Use manufacturer-approved conditioners or protectants designed for spa covers and pillows. Consult your retailer for product recommendations.
If you have questions about hot tub maintenance, we’re happy to help.
📞 800-222-0169
📧 customer.service@kingtechnology.com
You can also use the chat feature on our website for quick answers and support.
A little routine maintenance goes a long way. By keeping your water balanced, your plumbing clean and your cover dry, you can prevent mold and mildew from taking hold and enjoy a cleaner, happier hot tub experience all year long.
- CDC.gov What is mold?
