303® Mold & Mildew Cleaner + Blocker
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Key Features & Benefits
Dual-Action Mold & Mildew Protection
Cleans existing mold and mildew stains while forming a protective barrier that helps block future growth. This two-in-one formula restores surfaces and helps maintain a cleaner spa environment longer.
Safe for All Hot Tub Surfaces
Engineered for seamless compatibility with original mounting points for secure placement.Designed for use on vinyl covers, wood cabinets, fiberglass shells, plastic components, and more. The material-safe formula delivers effective cleaning without damaging sensitive spa finishes.
Bleach-Free, Non-Damaging Formula
Powerful cleaning performance without harsh bleach or corrosive chemicals. Won’t discolor, dry out, or prematurely age spa covers and exterior surfaces.
Long-Lasting Protective Barrier
Leaves behind a protective coating that helps prevent mold and mildew regrowth for 4–6 weeks under normal conditions, reducing maintenance frequency.
Ready-to-Use Spray Application
Convenient trigger spray requires no mixing or complicated preparation. Simply spray, wipe, and allow to dry for fast, hassle-free results.
Professional-Grade & Environmentally Conscious
Trusted by marine and RV professionals for over 40 years, this biodegradable formula delivers reliable performance while remaining safer for users and the environment.
Product Overview
The 303® Difference: Why This Brand Stands Out
303® Products has been the gold standard in protective treatments since 1980. Originally developed for aerospace applications, their formulas have been refined over four decades to deliver unmatched performance. Unlike household cleaners that contain harsh bleach or acids, 303® uses advanced chemistry that's tough on mold but gentle on surfaces.
The brand is trusted by professionals in marine, automotive, RV, and outdoor industries—environments where equipment faces extreme conditions. When you choose 303®, you're choosing proven technology that protects millions of dollars worth of equipment worldwide.
Surrounding Decks: Wooden decks, composite materials, and concrete surfaces around your spa benefit from regular cleaning and protection.
Storage Covers and Accessories: Thermal blankets, cover lifters, and other accessories stay fresh and mold-free with periodic treatment.
Frequently Asked Questions
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Clean your hot tub cover every 4-6 weeks during regular use. In humid climates or shaded areas, treat covers every 3-4 weeks. The protective barrier lasts 4-6 weeks under normal conditions.
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Yes! 303® is safe for vinyl, marine-grade fabric, Sunbrella®, and all common cover materials. Unlike bleach-based cleaners, it won't cause discoloration or premature aging.
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No, 303® is for external surfaces only. For interior cleaning and water treatment, explore our Hot Tub Chemicals and Spa Shell Cleaners collections.
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Yes, 303® effectively removes most mold and mildew stains, including black mold. Heavily stained covers may require 2-3 applications with gentle scrubbing.
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303® is specifically engineered for outdoor equipment, is bleach-free, provides long-lasting protection, won't cause UV damage, and is safe for specialized hot tub materials.
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A 16 oz bottle provides 8-12 applications for an average hot tub cover (7' x 7'), while a 32 oz bottle covers 16-24 applications.
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Absolutely! 303® works excellently on wood, composite materials, and synthetic cabinet panels, penetrating to eliminate mold at the root level.
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Yes, 303® is biodegradable and environmentally responsible. Normal runoff won't harm landscaping, and it contains no harsh acids, bleach, or toxic chemicals.
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