When you put a beer on tap the carbonation level is a function of temperature and CO2 pressure. In a nutshell… higher carbonation levels (or temperatures) require higher CO2 pressures. See: Balancing Your Draft System for more info.
Higher CO2 pressures need to be offset with appropriate resistance. A Hefeweizen at 20 PSI isn’t going to serve well with your typical 5′ of beer line. You need to add stuff to produce resistance so that when you’re beer hits the air it’s not speeding like a rocket ship toward your glass. Many times that’s done by increasing tubing lengths. That can work but does have some down sides. Chief among those, at least to me, is you can end up having a good amount of beer sitting in those lines. Temperatures are usually higher toward the top of your kegerator [See: Kegerator Beer Line Temperatures & Reducing Foam with a Recirculating Fan], so that means your first pint is still going to be foamy. This also results in some guesswork and requires that you swap tubing out when you change carbonation levels.
Keg Connection has just introduced a device to address these issues. Their new inline flow control assembly.
This allows you to restrict flow to reduce foam without the need for additional tubing or a specific faucet. You use the provided Allen wrench to adjust resistance. This means no adding additional tubing on a beer beer or carbonation level basis. Easy to disassemble for cleaning (or using an inline draft cleaning pump – See: Mark II Keg & Carboy Cleaner… As a Recirculating Draft Line Cleaning Pump). This is also made in Germany from food grade plastic and stainless steel.
Inline Flow Control – $49.95
At $49.95 it’s not what I would consider cheap. You can get a Perlick with Flow Control built in for about that price. The inline does have some advantages. It will work with any faucet and it requires a tool to adjust resistance.