Just a note.  The water tank on my '81 Westy holds 13.2 US gallons, or 50
liters, according to the camper manual that came with the vehicle.

----- Original Message -----
> The Vanagon tank was designed for the Vanagon, and at 5 gallons is just
the
> right size.  It holds about as much as your water tank does, and if you
empty
> one and fill the other at the same time you will be in good shape.