More newbie questions - black tank flush system

thanks, just saw a picture of one at "WOW! What a stench - almost gassed us out! "
seems like a poor design to me, dripping water on the inside of the RV?
I mean some folks have expressed concern about hooking a 30 ft hose to a flusher or sewer solution and getting feed back into the potable water and this seems to me to be a lot riskier?
bumpy