Personally, I don't travel with any water in my fresh water tank. The first reason is that 30 gallons of water is pretty heavy and it reduces the amount of camping supplies I can carry. The second reason is that the weight can affect how your trailer handles when towing. The third reason is I'm not convinced that any of the tanks under my trailer are very well secured to the underside of the camper...looks like the use a thin sheet metal clip around the edge and some flimsy pipe strapping. I recommend travelling dry and fill up your fresh water tank after arriving at your destination. Of course if your boondocking you would want to fill up your tank as you leave civilization.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.