Well, soda needs to be carbed up at a super high psi, compared to beer. I think mine was on about 40 psi for a week before it was nicely carbonated. Then, because it was such a high psi, I needed more line. I bought some cheap line from Mcmaster-carr (50 feet for like $6) and used about 30 feet on the root beer. That worked great. I tried to turn it down, but it lost carbonation at anything lower than about 38psi.
Broken Leg Brewery
Giving beer a leg to stand on since 2006