How to remove mildew from boat seats and canvas

The short version: Start with the mildest fix that works, and focus on keeping mildew from coming back. In recent Practical Sailor testing, Concrobium removed mildew and kept it from returning, and on vinyl, bleach did no better than milder acid cleaners on deep stains. Rinse, dry vinyl with a chamois, and keep the boat ventilated.

On this page: What recent testing found Steps Keeping it from coming back Common questions

What recent testing found

• Concrobium removed mildew from a test carpet and kept it from returning, even after the area got damp again. Practical Sailor called it the best performer in its testing.
• On vinyl, bleach removed some mildew but did no better than the top acid cleaners, and nothing removed mildew deeply embedded in old, deteriorated vinyl.
• Bleach can significantly weaken fibers, so keep it off canvas and lines.
• Basis: Practical Sailor mildew treatments test, about 2022 (exact date to confirm), and Practical Sailor's vinyl cleaning test, July 2024.

See our mildew remover picks.

Steps

1. Brush off loose dirt and rinse the area.
2. Try the milder cleaner first, a chlorine-free spray cleaner, following the label. Let it sit for the time the label gives.
3. Scrub gently with a soft brush. Do not use abrasive pads on vinyl.
4. Use bleach only as a last resort on vinyl, test a hidden spot first, and keep it off canvas and stitching, since it can weaken fibers.
5. Rinse thoroughly. Dry vinyl and hard surfaces with a chamois. Chamois canvas as dry as you can, then let it air dry completely.
6. Protect the vinyl afterward. See our vinyl care guide.

Keeping it from coming back

Mildew grows where moisture sits. Keep seats clean and protected with a UV protectant, dry everything with a chamois before closing the boat up, never put a cover on over wet seats, keep the boat ventilated, and clean small spots early.

Common questions

Is bleach safe on boat vinyl?

Use it as a last step, not the first. In recent testing it did no better than milder acid cleaners on deep stains, and it can weaken fibers in canvas and stitching.

Do mildew protectant sprays work?

Some do, for a while. Practical Sailor reapplied a mildew preventer every 90 days to keep a Florida boat's interior mildew-free. They are not a replacement for drying and ventilation.

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