I have the same issue.
I purchased a sewer cap that accepts a water hose.
The end of my sewer hose accepts the other end of the water hose. (see attachment)
I purchased a grey water hose that I only use for this purpose.
I make all of the connections and open the galley valve before I open the slideout.
I have been doing this for at least three years and it works great.
http://i284.photobucket.com/albums/l...t/image004.gif
Bill