You have a 2014 model....it will have a fresh water drain.
Look under rig around area fresh water tank is located for a pipe sticking out. Could have a valve on it, could have a plug or cap. You should also find two other pipes sticking out....low point drains. Could be valved or plugged/capped. Might even be red, blue or clear.
Towing with water in tank is not an issue.
Actually it's a good idea for several reasons........potti breaks while traveling, having water available should you break down on side of road, area you go to doesn't have water, water is bad at area you go to, power is out in area you go to etc.
Crawl around under rig and do a look-see......might be interesting in what you find.
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31