The Sewer Solution comes with a vacuum breaker back flow preventer. I've read where an individual also uses another back flow preventer at the water source end as well. When using a vacuum breaker it is important to turn on the water rapidly and to high pressure and conversely when turning the water off do so rapidly. Allowing gradual slow flow or weak pressure does not allow the device to work properly.
I also keep a spray bottle with a bleach solution to spray down things which might become contaminated, and certainly should be used to spray down a campground water service before you hook up.