Hi again Cindy:
Some Newells are built with just one waste water tank combining gray and black water together in the same tank, and therefore giving you a little more capacity for the gray water, which usually outstrips the black water production. In my case I have two, which equal 160 gallons, which is the capacity of my fresh water tank. I like having the separate gray tank as I can dump that pretty much anywhere....it's just dirty, soapy water. When we stay with friends we usually, with their permission, just water their lawn with the gray water...