The last third of a keg is foamy. As the beer is replaced by carbon dioxide in the keg, the area of contact between the gas and the beer stays the same, but the volume of beer is smaller. This allows the beer to dissolve the gas more quickly. This means that more carbonation gets absorbed into the beer, and your beer can more easily become overcarbonated. This is not usually an issue of the keg is used within a few days to a week. But for kegs that sit tapped for weeks at a time or longer this can become a concern, especially if there was just slightly too much co2 pressure on the keg to start with.
You can see above that you draw your beer from the bottom of the keg, so you don't begin to get the lighter, foamier over-carbonated beer until you reach the last of the keg. Ideally, we keep it from getting over-carbonated in the first place. But if it does happen, there are a couple of tricks you can use.
Here's what you can do:
1. Keep the beer cold. The colder the
34 degrees is better than 38 for reducing foam in slightly overcarbonated beer
2. De-gas the keg.
Shut the gas off to the keg at the regulator
(hopefully there is a shut-off valve)
Open the safety release valve on the keg to
release the gas
The safety release is circled in red, pull the ring out to release the head pressure on the keg.
Shake the keg for 15 seconds
Wait 3 minutes, then open the safety release valve again to vent the carbonation you just stirred up.
Turn the gas back on to the keg at the regulator.
Do not make the mistake of trying to adjust the pressure of the regulator down, because the reduced pressure will allow the Carbonation in the slightly over-carbonated beer to "Break out" of the beer and foam in the line, just behind any connections or the shank of the faucet. This will make the problem worse, not better.
To make sure your regulator is set to maintain the
perfect, ideal conditions for your beer, call one of our Draught Beer
specialists to come give you a free estimate for the repair or installtion
of a Beer Dispensing System. Intalls
best way to fight this is to make sure all conditions are as close to
ideal as we can realistically make them. The lines are straight
or smoothly curved (no "elbow" joints), the pressure is just high
enough to dispense smoothly, not too much. The lines are clean,
the beer is cold, and the lines are being cooled, chilled, or at least
insulated all the way to the dispenser. Remember, if the
beer warms it will release the co2 gas.. so if it gets warm in the
tubing on the way from the back room or beer cooler out to the bar,
then it will foam IN THE LINE, and this will cause your beer at the
dispenser to come out alternately clear and foamy, depending on how
many "hot spots" you have along the line.