Doser Help

[RCS]

I picked up this doser last month in Atlanta, and I'm just getting around to figuring it all out. The basics are rather simple: it's air-powered and lifts the liquid in the tube up and out, into the tank. That much I've figured out. What I can't figure out is the third tube, the black one circled in blue in the picture. I would assume it's some sort of input to hook it to a second vessel holding more liquid? If so, would it be a simple siphon device, or how would I go about using it. It would make my life much simpler, an air-powered device dosing a couple gallons of kalk every day that I simply refill every once in a while (once I redo underneath my stand, I should have room to fit a good 5g worth of kalk). Any help here?

http://reefcentral.com/gallery/data/500/81760doser.jpg

[imsqueak]

No instructions, cant figure where it goes, this time of year we get quick to say "spare parts". I've never seen one of these but I like the "spare parts" theory when I cant figure it out. Looks like a birds nest inside that reactor tube. What the heck is going on there?

[RCS]

The two tubes coming in form the top go into the bottom part, which has a hole covered by a rubber flap on the bottom. The air goes into the little cylinder on the bottom, and pops out the other tube in there, taking some water with it (works just like an undergravel filter or a larval collector). The rubber flap flips up to intake more water into the cylinder then. The "bird's nest" area in the very bottom is simple some filter material to keep chunks out, since the best use for this thing is kalk dosing. Unless you're referring to the clear tubes, in which case you just see the extra bunching up a bit, since the tubes were cut long to have room to work with when removing the top.