Yep, fill til it overflows. Are you mostly dry camping (no water hookups)? FWIW, if you have water hookup at your camp site you do not need to use the fresh water storage tank. The white hose you bought also hooks up at the city water inlet and provides the water directly to the sinks, toilet, shower, and water heater.
HTT: "EscapeII" 2016 Shamrock 23WS (current)
PUP: "Escape" 2010 Rockwood HW 277 (gone)
TV: "Bruce" 2011 Dodge Durango V8 Hemi Crew
Just us gals (me, Sis and our daughters)
Traveled 19520 miles and 209 nights in 7 years and counting