With our new Rockwood, I came up with a new word after taking her out a few times camping, "dribbling"
It seems that whenever I open the cover to hook up my hose on the main gray/black tanks, some liquid dribbles out...anywhere from 1/2 to 3/4 of a cup. I assume one of the valves is letting just a bit out...but I have been unable to determine if it's the black one or the gray. (In our old Nomad camper, she never dribbled.)
I just saw something that may end the dribbling (well, not end it but contain that small amount of liquid for when the hoses are hooked up)...its' called a twist-on waste valve that just goes right on the end of the connection...genius! (I found one for $18.99 on Amazon.)