air in keg line questions

[jigidyjim]

I've been reading the pet peeves thread and saw the part about the Perlick EKS Coupler.

I'm curious to learn how this works. I'm a bottler and have never really worked with kegs before.

My questions are:

1) Why does air in the line cause foam in the beer (I have theories but would love an actual answer)

2) If this device causes the line to stop when the keg is empty, won't that mean the next pour contains beer from the previous keg? I guess that would only be useful if you replace the keg with the same keg as before... which in reality is probably what most bars do.

3) For homebrewers, don't your lines always start with air in them? does that mean you lose a few pours of each keg?

Thanks!

 

[betarhoalphadelta]

1) It's not "air" in the lines, it's CO2. Not having a full line makes it *very* easy for the CO2 in the beer to come out of solution, so by the time it gets to the tap, you have tons of foam.

The principle (I've been studying this as I just built a new keezer and I'm dealing with foam issues) is generally that you want CO2 to stay in solution all the way from the keg, through the line, out the tap and into the glass. If the CO2 is coming out of solution in transit, you end up with pours that are most/all foam. Under pressure, this *shouldn't* happen (i.e the pressure stops any natural "air pockets" from forming), but if there is, say, a big temperature difference between the kegged beer and the tap line, you can have the CO2 coming out of solution and forming pockets of CO2 gas. When this gets spit out the faucet, you get a foamy pour (and a flat beer, as the CO2 is no longer properly in solution).

2) Yes, the next pour is full of beer from the previous keg.

3) Not a few pours. Most homebrewers aren't running 40-100' beer lines, as you'll see in major beer bars where the keg room and the taps are a long distance from one another. Most homebrewers are working with 5-10' lines. A quick check online suggests that you lose 1/6 oz per foot of line (3/16" ID beer line), so if you lose some beer, it's somewhere between 1 and 2 oz.

 

[jigidyjim]

Thanks. Exactly the info I was looking for.