How do you know when to wash your fly rod sac and replace the backing on your fly fishing reel? A quick, easy and accurate test is to smell them….If they smell like mildew wash the rod sac and replace the backing. I like to allow my fly rod and flyfishing reel to dry for several days at room temperature out of direct sunlight before storing it for longer than a day. You are reading this too late and you let your fly rod/ sac/ backing mildew? Depending on the degree of mildew, this could be the end of your fly rod. Clean your fly rod with a dish detergent and allow it to sit out to air dry for several days then check to see how badly it is damaged. Cork grips and rod wraps will be the hardest to salvage if they are soft after this drying period. Fly reel backing – replace it. Rod sac – wash it in a mild bleach solution and allow to air dry. This will discolor your rod sac but it will still be functional and protect your fly rod while in the case.