Airstream's specs for that trailer indicate that it's a combined black/gray tank, but it's 70 gallons so it's not a big limiting factor. The worst thing about it is that if you DO overflow the tank, the water in your shower will be a little extra icky, but it's not like graywater smells like roses in the first place. If you're careful with showers and dishwater you should be able to go a long while before filling the tank.
Il Carriaggio — 1975 Argosy 24 | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill