I carry one 10' water hose (spigot to water filter) and two 25' water hoses (to reach the trailer). I carry one 15' sewer hose. If that is not enough, I break camp when needed and go dump.
For the tank flush, my TT has a backflow preventer built in. I bought a 6' water hose and two more backflow preventers. I put one backflow preventer on each end of the 6' water hose. I feel safe using the 6' water hose attached to my drinking water hose as a flush. Three backflow preventers would all have to fail to contaminate it. (Those who demand a dedicated hose are still hooking their dedicated hose to the spigot where they get fresh water.)
I use a water filter whenever we fill the fresh water tank or use shore water because at one campsite in Florida (in 2009), I got sand in my water system and never got it out again (sold that RV in 2017).
Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB