We do NOT advise machine washing your backpack. This can be harmful to the structure and fabric of the bag.
Clean your rucksack and components in a bathtub or large sink using a mild soapy, warm water and a sponge or soft brush. Treat your bag carefully, don’t use harsh chemicals and give it a scrub with a soft sponge. Once you’re happy that your bag is cleaned, you rinse thoroughly. Make sure you remove all traces of soap in and outside of your bag.
Finally, hang it out to dry outdoors or in a well-ventilated area out of direct sunlight. Your bag will both drip and air dry to finish up. Ventilation is the key to prevent the bag from being damp for too long.