Just a couple of points to consider:
1. Make sure you can use tote tanks where you camp, as many State and Federal campgrounds prohibit the dumping of both gray and black water into their pit and flush toilets.
2. Even if you can dump, they may not have a convenient dump port and you may need a "maceration pump" to elevate the effluent to the toilet or drain pipe level.
3. If you are boondocking off the grid your black water tank should hold you for some time (mine is 35 gallons) and an adapter cap
Amazon.com: Valterra Products, Inc. T1020-1 3" Black Termination Cap with Hose Thread Connection your dump port will allow you to use a simple garden hose to dispose of the gray water with a 25 of 50 foot hose that reaches an appropriate leach field. Make sure you don't mix up the fresh water hose and the gray water hose! ;o(