The dreaded foamy pour is a common complaint among new kegerator owners and operators. While professionals enjoy the benefits of commercial-grade refrigeration and purpose-built draft systems, we home enthusiasts often cobble together our own setups from Craigslisted parts and fire-sale fridges. And diagnosing foam is almost always part of the process. If your draft system consistently serves supremely sudsy pints, you may need to get to know the muffin fan.
First things first. Before you start hacking your kegerator, make sure your draft system is balanced. A balanced draft system includes enough flow resistance in the beer lines and from gravity to just offset the carbonation pressure of the beer. For whatever reason, 5-foot beverage lines are standard issue for most kegerator conversion kits, but many find that longer lines (up to twice as long) are required for foam-free flow. So check your lines first. When in doubt, go long and trim back as needed.
Once you’ve convinced yourself that balance isn’t the issue, then it’s time to think about temperature. Warm air rises and cold air sinks, and most refrigerators don’t supply much in the way of internal airflow. So, it’s entirely possible, especially if you operate a draft tower, that beer exiting the faucets is 5-10°F (2.5-5.5°C) warmer than beer leaving the keg. And because warm beer holds less carbon dioxide than cold beer, it releases that excess carbon dioxide when you pour it. If the first pint is foam but subsequent pints are fine, then temperature is probably your problem (that first pour cools down the lines).