first of all I like to interroduce myself:
I'm new to this forum, live in Austria and I'm possibly going to buy a preowned Bambi 422 (=smallest european version of an airstream).
I learned that they use the so called Wastemaster (= flat portable wastewatertank that is lying under the trailer and is connected to the Drainage of the sink, etc.) to get reid of the wastewater. From my point of view this does not match with the idea of a touring trailer, it's more suitable for beeing on a campside for a week or so.
So my question is: anyone added a wastewatertank to his Bambi?
If you wonder about the nickname you may Google it and find the Airstream Bambi - Austria connection of the name