Sport-related stains, consistent washes and the passing of time cause that crisp, white polyester sport clothing to slowly yellow. The easiest way to keep it white is to maintain it not when it starts fading, but all the time, from the first wash onwards. White polyester clothing does require maintenance, but proper upkeep will keep it fresh and clean regardless of the grass, dirt and sweat stains it may be covered in. You will be able to keep this hard-to-clean synthetic fabric white in no time.

Turn the clothing inside out. While doing so, check the tag to make sure it's machine washable. Wash the polyester sport clothing often, if not after every use. Stains are removed best when still fresh.

Soak the clothing overnight in a bowl, bucket or the sink filled with half a cup of dishwashing detergent and about a gallon of warm water. This pre-treatment will get most stains out or at least make them less visible. You can tell by the dark color of the water once clothing is removed.

Wash the clothing by hand paying attention to tough stains. Rub them thoroughly but gently. Rinse the clothing in fresh, warm water and let it soak for another few minutes. Add half a cup of white vinegar while the clothing is soaking, and then rinse with clean water.

Soak the clothing in OxiClean if stains are not removed completely. You may use OxiClean rather than vinegar or soak the clothing in it overnight rather than in the dishwashing detergent, or you may use all solutions. Add a scoop of OxiClean to a bowl of water or as directed on the packaging label and soak for about an hour. Rinse the clothing with clean water.

Place the clothing in the washing machine. Add regular detergent and fabric softener which will help avoid static cling. Use warm water. Do not add colored clothing to this wash.

Dry the clothing on low tumble dry and remove while not yet completely dry. Over-drying polyester clothing may cause it to shrink.

Put the clothing away when not in use and away from sunlight by storing it in drawers or even in garment bags. Excess sunlight may cause the white clothing to yellow over time.