For waste water I would use one of those collapsible 5 gallon Coleman containers they sell at walmart. That way I don't muck up a rotopax and can replace it cheaply if it gets too foul.Campgrounds brings up another question - waste water from the sink. If you're staying in the wild, and not using anything in the sink that's not biodegradable, waste water could be handled simply with a hose out of the bottom of the sink that would reach far enough away from the campsite, but if you're in a campground you probably can't do that. If you're using a 2-gal. Rotopax for the water supply, a second 2-gal. container could collect the waste water. Anyone have any thoughts on waste water from the sink?.