From Sunbrella.com:

When it’s time for a thorough cleaning, Sunbrella fabrics can be cleaned while still on a boat or, size permitting, they can be removed for cleaning in a washing machine or dockside. When cleaning Sunbrella fabrics, it is important to observe the following:
Always use a mild soap such as Ivory Snow, Dreft or Woolite.
Water should be cold to lukewarm (Never more than 100°F/38°C.)
Rinse thoroughly to remove all soap residue.
Air dry only. Never apply heat to Sunbrella fabrics.


General or light cleaning:
To clean Sunbrella while still on a boat, follow these simple steps:
Brush off loose dirt.
Hose down.
Prepare a cleaning solution of water and mild soap such as Ivory Snow, Dreft or Woolite (no detergents).
Use a soft bristle brush to clean.
Allow cleaning solution to soak into the fabric.
Rinse thoroughly until all soap residue is removed.
Air dry.
May not require re-treatment depending on the age of the fabric.
If stubborn stains persist, you can use a diluted chlorine bleach/soap mixture for spot cleaning of mildew, roof run-off or other similar stains (see our Stain Chart for specific recommendations).
Heavy cleaning for stubborn stains and mildew

Sunbrella fabric does not promote mildew growth, however, mildew may grow on dirt and other foreign substances that are not removed from the fabric. To clean mildew, or other stubborn stains:
Eight ounces (one cup) of chlorine bleach.
Two ounces (1/4 cup) of mild soap and/or detergent.
One gallon of water.
Clean with soft bristle brush.
Allow mixture to soak into the fabric for up to 15 minutes.
Rinse thoroughly until all soap residue is removed.
Air dry.
Repeat if necessary.
Re-treatment of fabric for water and stain resistance will be necessary.

Remember to protect the area around your Sunbrella fabric if using a bleach solution. Carpet or other fabrics that are not Sunbrella may have an adverse reaction to the bleach. If a boat cover is suitable in size for a washing machine, these steps should be followed:
Use mild soap and/or detergent.
For heavier stains add 1 cup of bleach to wash.
Wash and rinse in cold water.
Air dry. Never apply heat to Sunbrella.
Re-treatment for water and stain resistance will be necessary after machine washing.


Re-treating the fabric:
As part of the finishing process, Sunbrella fabrics are treated with a fluorocarbon finish, which enhances water repellency. This finish is designed to last for several years, but must be replenished after a thorough cleaning. Based on test results, Glen Raven recommends 303 High Tech Fabric Guard™ as the preferred re-treatment product for Sunbrella fabrics. Fabrics should be re-treated after thorough cleaning or after five years of use.
For more information on re-treatment products, please visit www.303products.com.
* Synthetic fabric heat settings normally do not exceed 150°F/66°C.
Applying 303 High Tech Fabric Guard:

303 should be applied to Sunbrella fabrics after each thorough cleaning, which typically removes the original finish and reduces the fabric’s water repellency.

Clean Sunbrella fabric, using one of the cleaning methods:
Allow Sunbrella to completely air dry.
Apply 303 Fabric Guard in a well ventilated area following instructions on the container.
Apply 303 in a thin, even coat and allow fabric to dry completely.
Apply a second thin, even coating of 303. (Two light coatings are more effective in restoring fabric water resistance than a single heavy coating. A 15-ounce bottle provides coverage of up to 50 square feet of fabric.)

For more information, please visit www.303products.com.


Professional cleaners:
You may have access to professional cleaning firms. In evaluating the services of a professional firm, you should inquire about a firm’s experience in working with Sunbrella fabrics and knowledge of cleaning and re-treatment requirements. DO NOT dry clean Sunbrella fabrics.
Helpful hints

Protect the area around the Sunbrella fabric when using a bleach solution – bleach may discolor non-Sunbrella fabrics. Always rinse Sunbrella thoroughly to completely remove bleach.

Sunbrella air dries very quickly. Machine drying is not necessary.

If fabric has some wrinkling, use an iron, if necessary, but only on the synthetic* setting. As some irons exceed the recommended 100°F/38°C temperature on the synthetic setting, test a small inconspicuous area before ironing entire piece.

DO NOT use a steamer or iron set to steam setting.

Use of bleach and/or advanced age of the fabric application may impact the deterioration of the sewing thread and other non-Sunbrella components.