While white is a great color to reflect the heat of summer and let in plenty of useful light, it’s also a bugger to keep clean. There are no magic tricks to cleaning a shelter. It usually involves a good cleaner (Formula 409, Las Totally Awesome or the like), a brush and work. You also have to be realistic that it will never look as good as the day you first got it.
The fabric that your shelter is made from is vinyl coated nylon. In the coating are the UV and FR inhibitors which provide longevity to the shelter. If you scrub too much, you’ll probably degrade them.We do not recommend a pressure sprayer as it could actually loosen the coating.
Some recommendations: If there is a tent rental company near you they often have a very large washing machine to wash their tents. They may, for a price, (maybe $100.00), be willing to run your shelter through it. Do not go crazy with the hot water and chemicals. A relatively short cycle with warm water is all you should use. Be sure to remove the doors and straps. The gyrations of washing machine can kill a zipper and knit a mess with the straps. Wash the doors in a second load. They may actually fit in a standard commercial washer (Laundromat).
Try a scrub brush and spray cleaner. Lay the shelter out, spray it down with the cleaner, wait 5 minutes, scrub with a brush and then rinse. We use a stiff floor broom so we don’t have to crawl around on a wet shelter.
Whatever method you try, remember that the shelter has to be dry before you pack it away, otherwise mold & mildew will grow and that stuff is practically impossible to remove. And speaking of m&m, we find a dilute solution of bleach will lighten it. So will extended exposure to sunlight. A 10-20% solution of bleach and water is the mixture. If you try straight bleach, it will probably damage the coating.