Originally Posted by
Kent Wallace
Because air-lifts are a gravity flow concept, the air needs to be seperated from the upward column as soon as possible. A sweep at the top will allow the air to seperate before the horizontal flow starts as it will collect toward the top of the arc. As the water turns, the arc leaves water that is more dense at the bottom of the arc without the air to move it as much.
In my original tests I noticed a dfference in measured flow and I even used upside down DWV tees to help seperate the water from the air at the top. Not really necessary though, just a good fairly sharp turn into a chamber that can allow the seperation.