I carry a couple of the GREEN 6-gallon plastic water cans (OZARK BRAND I think) for fresh water and two of the Reliance Aqua-Tainer 7-gallon for GRAY water from the sink etc... I also have a foldable two wheeled tote to transport these back and forth from where I am setup.
My off-road camper trailer has a front deck and these items store great on it. When going into to my camping spots I always make note where fresh water is available and most often this is primitive toilet building and they usually have fresh water available here with an outside spigot...
This is where I will dump my gray water if not allowed to dump on tree roots. I bring my cassette potty 6-gallon tank here as well and dump it down the primitive toilet...
Roy Ken