When I said every nook and cranny, here is a 40 gallon fresh water tank that fits under an Advanced RV Sprinter. Otherwise, 26-30 gallons seemed to be the upper limit.
I don't think it will be a problem. About the only way you clean fresh water tanks is with bleach and filtering before filling in the first place.
With the two Sprinters I owned the black tank basically was above the floor elevating the bathroom floor. There is a practical limit of about 10 gallons that way in a B. First thing I noticed about the Advanced RV was the bathroom floor was not elevated the usual 4" or so yet they are putting in an 18 gallon black tank. That means they have utilized space under the chassis. It doesn't have the nooks and crannies of the fresh water tank.
The Coach House Arriva could be a fulltime B, IMO. It is zoned right to not be too stifling and does have the decent bathroom. But seriously, I've met and read about fulltimers in Class Bs to know it can be done. We've been out as much as 3 months at a time and it was all kind of bittersweet when returning home.
When you think about it, most Class Bs are better equipped and are about the size of the many tiny houses that are the current rage right now in the media. Mostly young people are building tiny houses anywhere from $5,000 to $50,000 and living in them. They probably aren't able to buy Class Bs from $50,000 and up or afford the travel if they are in the work force.
