I took a double "Y" hose valve and screwed the hose to the single female side, screwed one of the male sides to the city hook up, made a very short hose from my damaged fresh water hose, and screwed the female to the "y" and the short hose to the black water sprinkler. When I drain my black water, I turn off the ball valve on the fresh water "Y" side, then open the ball valve on the sprinkler side, very easy and never had a problem. My Pinnacle is a 2012, so it sounds like the new ones do it totally different.
2012 36REQS Pinnacle w/ Reese GooseBox
Stays at Lakehills, TX on Medina Lake most of the year!!
Chevy Silverado 3500 Duramax Dually