If you are at a campground with a sewer hook up, you put the slinky hose
from the outlet of the trailer into the hole. The grey water just goes
down the hole. The black tank can go for nearly a week. Keep that valve
closed until the tank is quite full, and don't be stingy with the water
to flush. It needs to stay sloshy. You can either dump the black tank
right into the ground , followed by a good rush of water through the
hose or take the trailer to the dump station.
If you are not at a sewer hook up, you need the blue meanie to hold the
grey water. I have a 5 gal that takes me a day to fill, then I can
empty it easily. The big ones are way heavy when full.
I don't think most folks use the blue meanie for black water. They
don't drain all that well, and I would be afraid of it stinking while
it's riding in the truck.
Daisy