SnoGhost, many are under the misconception that hauling the water will greatly affect gas mileage, when in fact, a full tank will only cause a fraction of gas mileage loss. the air resistance of the RV will be a much bigger factor in gas mileage. 200-300lbs. extra water weight will barely be noticed.
also, many are towing with marginal tow vehicles, like minivans, and have to account for every ounce of weight to not be over their towing/hitch capacity.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC