Originally Posted by Davydd
Historically RVs had single waste tanks. Separating black from grey is a more recent refined development and you find one converter out of all that either is not with it in how people use Bs, is looking for a cut corner cheap solution or hasn't been in the market all that long. Who really knows? Are you even sure it is a single tank? Brochure information is not always clear or accurate. I think Avanti alluded to his first Airstream having a single tank? I know my vintage Airstream trailer had a single tank but Airstream no longer does that. They evidently learned. Airstream, Roadtrek, Winnebago, Pleasure-way, Leisure Travel Vans, Advanced RV and all disagree. Those in the business have all gravitated to the two tank system and it was not driven by customers but from their own common sense practical space matters working out the details. That's a lot of overwhelming agreement.
To answer your question, there is no question that the Avion Azur B uses a single waste tank. You can take that to the bank. Their Class B volume I am guessing is somewhere between ARV and LTV and after three years if their single tank approach produced the draconian consequences suggested on this thread, I doubt that they would still retain the design.
Avion has been in the trailer business quite a while and this is their first and only Class B product which they have been producing for around three years. Their trailer history doesn't guarantee success in Class B design, (the warts reported in Airstream's B demonstrates this), but they are certainly no strangers to waste tanks and were fully aware of the conventional two tank approach when they decided to implement a single tank.
So, the good news is that unlike some discussions that never leave the theoretical, at least there is a real world case where a single waste tank is being supplied in a Sprinter B and history will eventually demonstrate whether the owners love it or hate it or more likely, IMO, just accept and adjust to it.