It is important to properly clean your composite decking to help keep it looking fresh and new. Here are some proper care methods that Green Bay decking recommends:

POWER WASHING

Periodic cleaning with a pressure washer will help keep your deck looking its best. Proper use is very important, so please follow all manufacturer instructions and use proper safety precautions when operating a power washer. The power washing unit should be set at a lower pressure setting, and use a fan tip nozzle. Spray should be consistent with the grain of the product. To prevent damage to the boards, be careful to stay a minimum of 12″ off the surface and do not let the spray sit idle too long.

REPAIRING SCRATCHES

Simply use a stainless steel wire brush to remove scratches. A few strokes along the grain will most likely refresh the deck board. Always test a small area to assure that the surface texture is not removed.

REMOVING OILY STAINS

For oily stains such as gasoline, butter, mayonnaise, etc., use concentrated dish soap or laundry detergent along with a plastic bristled scrub brush.

REMOVING MICROBIAL STAINS

Microbial stains, such as algae and black mold, do not damage our boards. For the most part, algae and black mold sit on the surface and consume pollen without degrading the board. These types of stains can be removed by the use of a pressure washer, plastic bristled scrub brush, and cleaners designed to remove mold and mildew.

Source: http://greenbaydecking.com/care-and-clean/#1466553790737-d4056b5f-783b