Beer line lengths play an important role when kegging your beer.
The resistance needs to be calculated based on each particular setup. If you are using a direct draw setup (such as a kegerator/keg fridge) you will have to make sure you have some resistance in your system. Resistance can be created several ways but the easiest is just to increase the length of the beer line.
For 4mm ID (internal diameter) beer line the length should be 1.8-2.5m, for
5mm ID beer line the length should be about 3-4.5 meters.
6mm internal diameter the length should be 5-10 meters.
FAQ: Can you turn down the pressure on your regulator and use a shorter beer line to reduce foaming.
No..Because if you have the pressure too low on your kegs, the beer will lose carbonation.
NOTE: It is important to also make sure you pressure on your regulator is set correctly based on the temperature that you have your beer sitting at.