WATERPROOF GARMENT CARE:
Shell garments should be machine washed in warm water with a powder detergent, and dried in a warm, low heat, dryer. For optimum performance you may also need to re-activate the DWR (durable water repellant) finish on your water-repellant garment from time to time. Never dry clean.
All waterproof/breathable shells are treated with a DWR (durable water repellant) finish. The DWR helps water to bead up on the surface of the jacket, rather than soaking into the fibers of the shell, where it can impair the breathability of the membrane or coating that allows the fabric to function.
Over time, the DWR gets worn away, most commonly in areas of abrasion such as the sleeves and shoulders of a jacket, or the seat and knees of pants. Retreating your garment is usually a simple affair, using one of the widely available spray-on DWR treatments for waterproof/breathable garments such as Nikwax, TXDirect, Techtron, or Reviv-X (marketed by W.L. Gore). Wash-in treatments are also available although they tend to be less effective than the spray treatments. Often a DWR can be revived simply by washing the garment in a powder detergent, rinsing thoroughly, then tumble drying at a moderate heat for 30-40 minutes, or running a warm iron over the surface of the garment. The heat application is an important element in activating the DWR properties of a spray treatment, and most of the treatments listed above recommend that some form of heat be applied to the garment after it is treated.
Courtesy of Kelty