Backpacks are made of nylon, so any mild detergent should do fine. As for the support pannel, if it is plastic it can get wet, but you may want to take it out so the pack is not so stiff. I wash my pack in the bathtub - soak it overnight, pull the plug and then run the shower (cold water) for about 20 minutes. The most important thing is to get it fully dry so you do not get mold. I luckily have a front-loading washer, so I can put it in on the spin cycle. I put the entire pack in a cotton duffle so that nothing gets caught in the little holes in the washer tub. I then hang it outside in the sun (100degree heat)! For some reason I am a bit hesitant to do the entire washing in the front-loading machine. I guess it is because once I washed a tent fly in the washer and the waterproof coating disintigrated! I think it had more to do with the fly being very old and damaged by UV light. But packs generally are not made of coated nylon so I think it would be OK.