Wash and store a down jacket without flattening the fill
Follow the garment label, use an appropriate down cleaner, dry fully on permitted low heat and store uncompressed.
Down fill can clump and lose loft when dirty or wet. REI's care guide emphasizes garment labels, suitable down washing, thorough low-heat drying and uncompressed storage. Not every insulated jacket can be machine washed or tumble dried, particularly those with special coatings or mixed materials.