When using a ball valve in a keggle a dip tube is needs to be installed. Do a quick search here to find various designs. There are a million different ways to make one work for your set-up so just take a look and see what's right for you. With a dip tube properly installed you can get all that sweet sweet barley water out of the keg and into the fermentor.
Cellar Door Brewery
Primary: Smoked Porter
Secondary: Flanders Red 2010
Kegged: 10.10.10, Robust Porter, American IPA
"Without algae, there would be no life on earth, the seas would be sterile and the land would be uncolonized."
-Sir David Attenborough