Most gray tanks I have seen added to vintage Airstreams protrude below the belly and have a separate outlet from the black tank.
I am interested in installing one of Vintage Trailer Supply's new gray tanks which are designed to fit within the belly skin. However, I haven't figured out how to plumb it to retain a single outlet. Currently the gray water exits via the black water outlet. The 1-1/2" gray water line T's into the vertical 3" outlet below the Thetford valve.
Has anyone figured out how to do this. I would have to remove the belly skin to figure out how to design this, and I prefer not doing this allowing for the possibility that it is impossible.