Originally Posted by max384
I'm actually pretty confused as to why it seems that everyone on this site uses 10' serving lines. Are people just blindly using 10' lines without actually doing the math to balance their systems? Or are they serving at very high PSI? I tried 10' lines and was left disappointed. I did a little bit of math and balanced my system, and I now have the perfect pour.
The warmer the beer is or the more highly carbed it is, the slower/gentler the pour needs to be to prevent CO2 from breaking out of solution during the pour, causing excessive foam. Most homebrewers like to serve their beer slightly warmer than commercial set-ups, which requires longer lines to slow the pour down enough. For the average homebrewer, 10-12' works very well. If you were maintaining ~36° beer temps and using a moderate-low carb level, then you likely found the pour to be a bit slow using 10' lines. It's a much easier fix to trim a few feet off of the lines in cases like this than it is to replace lines that are too short, which is one of the reasons you see so many suggestions for 10' lines.
If by "doing the math" you mean using one of the many line balancing calculators or formulas online, the reason many people don't use them is because they're flawed. They all assume commercial serving conditions (~36° and <2.7 vol carbonation), and the only thing they calculate is the line length required to result in a 1gal/min flow rate. Unfortunately this flow rate is too fast for the average homebrewer set-up, and will result in excessive foaming. Even the terms are misleading, as "line balancing" and "ideal line length" imply that there's some negative effect to having an extra long line. The only potentially negative impact is a slightly slower pour, but it allows serving at a wide range of carb levels and serving temps. If I were running a bar where the speed at which I could fill pints might affect my bottom line, then I'd want the pour to be as fast as possible without excessive foaming. But in my home bar, if I have time to drink a beer, I also have an extra second or two to wait for it to pour. :shrug:
Originally Posted by chickypad
The line I buy is supposed to lose about 2 lb per ft. So at the 13 psi serving pressure I have that should require 7.5 ft. I will tell you though in practice it doesn't work. I started with 8 ft and moved up to 10 and now they pour perfectly.
Edit: meant it should need 6.5. Even 8 wasn't long enough.
That's a common misconception. The resistance of a given line is not a fixed value, it's dependent on the flow rate. The 2 psi/ft figure is only valid at a flow rate of 1 gal/min, which is what most commercial systems aim for. If you're serving above ~36°, 1 gal/min will liikely be too fast and cause excessive foaming. The calculator linked below is the only one I've seen that accounts for this very fundamental fluid mechanics principle.
Originally Posted by day_trippr
None of the above.
Unlike nearly every "line length calculator" that uses beer line resistance values that aren't actually applicable to most home dispensing systems, some of us use a much better calculator
written by an author who actually understands the various factors that go into picking the most reliable solution.
It shouldn't be missed that the vast majority of the "Help! My Pours Are Too Foamy" Threads involve the classic 5 feet of 3/16" ID beer line...not those with 10+ foot runs...
Cheers! ("Hail Science!"
This. The only tricky part is figuring out what to input for the pint fill time. The warmer or more highly carbed your beer is, the higher it should be. At 36° and 2.6 vol, 7 sec works pretty well. At 40° and 2.5 vol, you'll need it closer to 9-10 sec.