Cleaning your gear on a regular basis will maintain it's longevity and keep you smelling so fresh and so clean, clean! Additionally, cleaning your gear is easy and requires just two things - water and soap.
Rinse your rucksack with fresh water and soap, flip it inside out (pro tip) and rinse it some more. Then hang to air dry. Under no circumstances should you use a machine washer or dryer (any damage from a washer and dryer will also void the SCARS Guarantee). The rucks can withstand a summer or ten in Baghdad just fine, but the concentrated heat from dryers will warp some of the lamination in the back panel and shoulder pads.