Seasonal, No Sewer Hookup, What to Do With Black Tank

I've used my blue boy tank for both gray and black. I see no difference in using it that way. In either case you must be careful not to fill it too far and be careful when you dump. It rinses out well and does not give off odors when not being used.

Op, I would get a 22-30 gallon blue boy tank and use it. Sure beats unhooking all the connections, unleveling, pulling in slides, and re-doing it all over again after you take the rig to the dump station.
Barney