I would not go more than 4 days depending on where the water came from.
If you do decide to keep water in the tank I suggest you fill it to reduce the amount of air as much as possible.
2016 F350 6.7L LB CC Reese 28K 2014 Chaparral Lite 266sab
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." 2014 19 days camping 2015 17 days camping201620 days camping