If I boondocks, I fill fresh from home, black and gray dry Drinking water we get from a jug in the fridge. If we run out we fill somewhere, but drinking water is still jug in the fridge and we buy another at the store if needed. That way we don't have to worry about getting bad fresh water. Same if hooked to campground/city water. Reason being we've been to lots of places that don't tell you thier water is for washing only (ie: arsenic, etc) unless you ask. They should, but very often don't. Or it's a tiny sign somewhere or an "oh, by the way" comment somewhere in a lot of other information passed on.
Black and gray we use until full, then find a dump site. Lots of places to do that for a small fee, both camp sites and fill stations.
We just watch our water use to make sure we get what we need done before needing to find a dump station.
I've weighed with all 3 tanks mostly full and we're under the trailer gvwr and also the truck's gvwr so I don't worry about towing full. Although I prefer to tow empty if I can.
2011 Flagstaff Classic Superlight 831RLBSS "Atrium slide"
Husky Centerline Hitch
2016 Ford F-150 EcoBoost SuperCrew, Lariat Sport, Max Tow package