Hi again everybody, thanks for the great info and advice.
My 2011 26BH does have an 80 Gallon fresh water tank, and the 699 lbs listed for weight on the vehicle decal (driver's side near front) confirms that.
I must have lost a lot of water backing up the driveway the first time and then driving up some extremely rough roads.
Also, it appears that either the take-off tube or the sensors (or panel) are not setup quite right. It says 1/3 on the panel, when we start to get empty.
At least I know the variables now, and how to quieten that pump... the dealer says it supoosed to sound like a gatling gun!?
2011 Jay Flight 26BH
2007 Chevy Silverado Classic, Ext. Cab, 4x4, 5.3l HO (L33), Z71, HD Tow Pkg, 4.10 G80
Hopkins 'Agility' Brake Controller
Husky WD Hitch (600-800lbs)