Originally Posted by gnef
hm, 8 ft of line is a bit in the area where it is difficult to say what to do exactly. so generally speaking, 3/16'' ID smooth bore thick walled tubing will have a pressure drop of about 2 psi/ft. so for you to be able to pour effectively, you will need to be using about 18 psi. if you want about 2.5 volumtes of co2 at this pressure, your temp will have to be about 50F, which is on the warm side for serving beer normally.
i would say that if you wanted to serve at 36F, with about 2.5 volumes of co2, you'd have to go to 1/4'' line, and use a significant amount. i can't remember the pressure drop of 1/4'' line, but someone here should know.
that sounds like quite a nice setup you will have though. have fun with it!
All that will happen if he uses 8' of 3/16" ID beverage tubing and goes with 10 psi is that the pour will be a bit on the slow side. The pressure drop will never cancel out the flow completely even if you have 100' of 3/16" ID tubing and are serving at 1 psi you will get flow out of the end of the tubing, albiet very slow.
There is a large set of variables involved in balancing your system. The higher the carbonation level - the slower you want the pour. The faster the pour the quicker the coČ will be knocked out of solution during the pour.
The rule of thumb that I use is:
Carb level = Desired Pour rate = Effective 3/16" Line Resistance at that given volume of CO2
1.8 to 2.3 volumes = 110-120 oz/min = 2.19 lbs/ft
2.4 to 2.6 volumes = 100-115 oz/min = 1.81 lbs/ft
2.6 to 2.8 volumes = 90-105 oz/min = 1.40 lbs/ft
2.8 to 3.0 volumes = 75-85 oz/min = 0.94 lbs/ft
So you can see that just using the 2 psi per foot pressure drop figure for 3/16" ID beverage tubing to balance your system does not take all factors into consideration.