In my system, I pump from the sump tank (under the GBs) into the FT. The pumped water runs up a 1/2 CPVC pipe (because it fit the pickup hose of the pump) it then goes to 1/2 reg PVC with a 90 elbow going to 1 one inch pipe. The 90 elbow has a small hole drilled in it. The theory is the water going down the bigger pipe sucks air into the small hole. This air is forced down the 1 inch pipe and I would imagine that the air is violently opposed to being forced down 6 inches of pipe. I know that air goes down the pipe because I see tiny bubbles emmitted from the bottom of the pipe.