Spray the white patio furniture down with a garden hose. The water from the garden hose will help to remove any loose debris and will get it wet enough to begin the cleaning process.
Fill a bucket with warm water, and add 1/4 cup of dishwasher powder. Use a scrub brush to apply the solution to the white patio furniture. Scrub the patio furniture with the solution until it comes clean, and give the patio furniture a rinse with the hose.
Use a mildew remover. For tough stains that refuse to budge, use a bathroom mildew cleaner that contains bleach. Spray the patio furniture with the mildew cleaner, and let it sit for about 30 minutes. Use a plastic scrubby to remove the stains, followed by a rinse with the garden hose.
Try a solution of one tbsp. liquid laundry detergent, 3/4 cup chlorine bleach and one gallon of water mixed in a bucket. Use the solution on tough stains and discolorations; apply it with a sponge or scrub brush. After scrubbing, remove the solution with a garden hose.
Get out the power washer. A power washer adjusted to the lowest setting can help to remove stains and make white patio furniture look like new again. If you do not have a power washer, consider taking your patio furniture to a do-it-yourself car wash. This way you can hose down and soap up the white patio furniture. After the stains are removed, add a spray wax that will cause rain water to bead on the surface.