Almost all draft beer problems are temperature-related and are the most important detail to consider for storage and dispensing beer from the keg. Ale and lagers are considered most flavorful at 38° F. Most keg draft beer packaged in the U.S. are not pasteurized, so it must be kept cold, preferably between 36-38° F. When temperatures rise above 50-55° F, bacteria growth rapidly begins to spoil the flavor and cloud the beer. Simply put, keg beer storage can be compared to milk storage: "if it is not kept cold, it will spoil."

It is most important to check the "liquid" temperature rather than the air temperature where the keg is stored. An ideal method for accurately monitoring the liquid temperature (inside the keg) utilizes a wall-mounted thermometer enclosed in a casing filled with liquid. Always calibrate the thermometer before mounting and place it in an area nearby kegs but possibly in a corner to prevent damage.  

To calibrate thermometers, fill a glass with ice (crushed preferred), then water—last top glass off with additional ice. Swirl thermometer probe in the ice water to acquire reading. If not 32° F, adjust accordingly.  

Another method for monitoring the liquid beer temperature inside the keg is to place a glass or bucket of water nearby or on top of the keg and allow it to chill for 24 hours. Then with a calibrated thermometer, determine water temperature, which simulates beer. If beer is being dispensed at a remote location from keg storage, monitor beer temperature being dispensed from the faucet to assure 36-38° F temperature is maintained to the glass.

To monitor, dispense a full glass to acclimate and dispose of beer. Dispense a second pour in the same glass. Utilizing a calibrated thermometer, record temperature. If warmer than keg storage, this indicates the system has issues maintaining temperature throughout. This monitoring method is ideal for determining beer temperature in the keg for kegerators or systems (direct draw) where the keg is a few feet from the faucet.

Attempt to limit the traffic in and out of a walk-in cooler as opening and closing the cooler door will increase storage temperatures. An alternative solution is to install flexible clear plastic or electric air curtain at the door, preventing air movement.