http://www.micromatic.com/draft-keg-beer-edu/line-cleaning-aid-71.html <div>Foamy draft beer can be caused by the build up of bacteria, yeast, mold, and beer stones within a beer line. Dirty beer lines lower the quality and taste of beer. It is important to regularly clean beer lines, faucets, and keg couplers to ensure the dispense of high quality beer.&nbsp;&nbsp; </div>