I kegged about 3 gallons of my first brew ever Saturday morning and then I force carbed it. I read on here to try a line arond 6 feet long. I'm getting alot of air in my line and lots of foam. I currently have the regulator set at only 3-4 pounds and it seems to have plenty of pressure. I was reading a brew book and it says to have the line as short as possible. What is correct and what causes air in the line?