Our objective was to design and install a sink, shower, and toilet system that requires no vent stack sticking up through the roof. Sticking with our wants of keeping our Sprinter as stealth looking as possible.
First, we are eliminating the need for a traditional black water holding tank. One typically mounted under a vehicle. Plumbed to, and vented through the roof in a traditional RV.
We opted to go with a self-contained cassette toilet. With its own holding tank, and own fresh water tank, and electric flush.