I have a 22 gal. blue tote. Generally, I dump to the tote when the grey or black tank is showing 3/4 full. The tote size is just right to empty the tanks and then I can connect it to the TV hitch to tow to the dump station. When you are choosing a tote, remember the weight of water is 8+ pounds per gallon. The tote will get very heavy quickly and manhandling it is not fun when full. The larger the tote, the more difficult it is to manhandle it to the TV, in the back of a truck or any other way to move it to the dump station.