I have BackFlowPreventive Valve in front of my house with 4" pipe after I remove the flapper, but since I would have to move my camper from normal parking spot, I found it more convenient to use Sewer Solution with 1" plastic pipe extension to dump.
Sewer Solution is using water pressure to grind and push the waste, so it is cheap to operate and having some slope, I can let gray water to go without the boost.
For those using septic tanks, don't you have a problem with RV waste?
After sitting in tanks for few days it is consider hazardous waste and I wonder if that is the fact, or just green propaganda.