You are talking about an AVC, but what you really mean is air release. You don't have air releases on jet pumps...
I don't know if you just like splitting hairs or you have un uncontrollable urge to correct me. If it releases surplus air, it controls the volume, so it's an AVC. WellMate calls it an air volume control on my tank. http://www.wellmate.com/en-US/produc...connect-series
Originally Posted by Texas Wellman
...it's not the air pressure. It's always the volume.
It's a pressure vessel. One cannot have air volume without pressure and still have useful drawdown. Not even in Texas. The volume of air under pressure acts like a spring to push the water out of the tank. Without pressure, you have only gravity. Put the tank on the roof and we won't need to have this discussion.