We have the 2008 View and the manual says to open the black water valve and empty that first. Then close the black water valve and open the grey water valve to empty that. There is no pump involved in hours.
In addition I have an adapter from CW where I attach the hose and backfill some water into the tanks to flush them out better.
MOTHER SHIP Winnebago View 24H (2007 Dodge Sprinter 3500 Chassis, 2008 Body)3.0 L M-B Diesel V6 bought used with 24K miles. Toad: ROCKY the Flying Squirrel.