The problem with using a socket is that the rod droops in the socket, so you actually have to have the socket at an angle to the WH so the rod is perpendicular. Start it slowly, trying to keep the socket at an angle while the rod stays perpendicular. This means the rod will be moving inside the socket.
The suggestion above about stuffing some paper in the socket MIGHT help keep it in line with the socket, in which case you should be able to screw it right in. I'll probably try that next time I have to drain my WH.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10