I work at a retail growler shop and we've had some issues with beer lately. Several beers that pour just fine at our sister shop have been "foamy" lately. We first thought they were over carbed kegs, and tried bleeding excess air out. However, after I noticed they were beers that poured fine at other growler shops, I took a closer look at the line.
When we pour, certain taps will pour beer for a few seconds, then a huge air bubble hits the beer and causes a ton of foam. Upon further examination, at the beginning of the day I can go back in the cooler and see air pockets forming either at the highest point or closest to the coupler on the keg.
A little more about us:
-We have 3/8ID line coming from the keg up to a compressor. After the compressor, the beer goes through 3/16ID line and out of the tap.
-I think the high point of the lines is about 7 1/2-8 feet up.
-We pour almost all of our beers between 10-12psi. I believe this is appropriate for filling growlers. Sometimes we may go a bit under/over that range depending on keg carbonation levels.
-Our floating thermometer in the cooler says it's 39F inside, but the kegs with the most foaming issues are closer to the cooler door, where I am guessing it is a few degrees warmer by the end of the day.
-Our shop is a sort of garage, and we have a 12 foot wide garage door open for the entire day most days, unless it's colder than 40F outside or extremely windy/rainy. I have reason to believe that 90F+ days are stressing the beer a bit. Additionally, condensation forms on the taps, which I can't decide if that's related to humidity in the air or a bad difference in temperature between the outside and the immediate area around the taps.