Draft system line balancing
by Steve Jones

Many homebrewers have problems setting up draft systems for homebrew, ranging from foamy beer to under or over carbonated beer. I have used information obtained from http://kegman.net/balance.html and from http://www.simgo.com/draft1.htm to develop this information for homebrewers.

Both of these sites are geared toward commercial draft systems, and base their calculations on using a higher than equilibrium pressure on the keg to push the beer. This will cause the beer to absorb additional CO2 over time, resulting in overcarbonated beer. Both sites stress that the entire keg needs to be dispensed in a relatively short period of time (a few days).

We homebrewers usually have several kegs on tap for somewhat extended periods of time (several weeks to a few months) and this would be unsatisfactory for us. So we need to maintain a balanced system to keep our beer from losing or gaining carbonation while it is on tap. When I refer to a system being balanced, it means that you maintain a constant temperature and CO2 pressure on your kegs to maintain a consistent carbonation level in your beer, and calibrate the line size and length to dispense the beer without an excess of foaming or carbonation loss.

In order to achieve this, there are several factors that need to be taken into consideration:

• CO2 pressure
• Keg temperature
• Desired volumes of CO2
• Length of beer line

CO2 Pressure, Keg Temperature, Desired Volumes of CO2

The CO2 pressure needed to achieve the desired volumes of CO2 is a function of temperature. Here is a rough guideline to the levels of CO2 for different styles of beer:

Carbonation Guide
Beer style	Volumes CO2	Beer style	Volumes CO2
British-style ales	1.5 - 2.0	Porter, Stout	1.7 - 2.3
Belgian ales	1.9 - 2.4	European lagers	2.2 - 2.7
American ales & lagers	2.2 - 2.7	Lambic	2.4 - 2.8
Fruit lambic	3.0 - 4.5	German wheat beer	3.3 - 4.5

And here is a table of CO2 pressures to achieve specific levels of CO2 at various temperatures. Find the desired volume of CO2 across the first row, and the temperature of your storage system down the first column. The intersection of these two values shows the CO2 pressure needed to achieve this:

Carbonation Chart
		Volumes of CO2
		1.5	1.6	1.7	1.8	1.9	2.0	2.1	2.2	2.3	2.4	2.5	2.6	2.7	2.8	2.9	3.0	3.1	3.2	3.3	3.4	3.5
	33						3.9	4.9	5.8	6.8	7.8	8.7	9.7	10.6	11.6	12.6	13.5	14.5	15.4	16.4	17.3	18.3
	34					3.3	4.3	5.3	6.3	7.3	8.2	9.2	10.2	11.2	12.1	13.1	14.1	15.1	16	17	18	18.9
	35					3.7	4.7	5.7	6.7	7.7	8.7	9.7	10.7	11.7	12.7	13.7	14.7	15.7	16.7	17.7	18.6	19.6
	36				3.1	4.1	5.1	6.2	7.2	8.2	9.2	10.2	11.2	12.3	13.3	14.3	15.3	16.3	17.3	18.3	19.3	20.3
	37				3.5	4.5	5.6	6.6	7.6	8.7	9.7	10.7	11.8	12.8	13.8	14.9	15.9	16.9	17.9	18.9	20	21
	38				3.9	4.9	6	7	8.1	9.1	10.2	11.2	12.3	13.3	14.4	15.4	16.5	17.5	18.6	19.6	20.6	21.7
	39			3.2	4.3	5.3	6.4	7.5	8.6	9.6	10.7	11.8	12.8	13.9	15	16	17.1	18.1	19.2	20.2	21.3	22.4
	40			3.6	4.7	5.7	6.8	7.9	9	10.1	11.2	12.3	13.4	14.4	15.5	16.6	17.7	18.8	19.8	20.9	22	23
	41			3.9	5.1	6.2	7.3	8.4	9.5	10.6	11.7	12.8	13.9	15	16.1	17.2	18.3	19.4	20.5	21.6	22.6	23.7
	42		3.2	4.3	5.5	6.6	7.7	8.8	10	11.1	12.2	13.3	14.4	15.5	16.7	17.8	18.9	20	21.1	22.2	23.3	24.4
	43		3.6	4.7	5.9	7	8.1	9.3	10.4	11.6	12.7	13.8	15	16.1	17.2	18.4	19.5	20.6	21.7	22.9	24
	44		3.9	5.1	6.3	7.4	8.6	9.7	10.9	12.1	13.2	14.4	15.5	16.7	17.8	19	20.1	21.3	22.4	23.5	24.7
	45	3.1	4.3	5.5	6.7	7.8	9	10.2	11.4	12.5	13.7	14.9	16.1	17.2	18.4	19.6	20.7	21.9	23	24.2
	46	3.5	4.7	5.9	7.1	8.3	9.5	10.7	11.8	13	14.2	15.4	16.6	17.8	19	20.2	21.3	22.5	23.7	24.9
	47	3.8	5	6.3	7.5	8.7	9.9	11.1	12.3	13.5	14.7	15.9	17.2	18.4	19.6	20.8	22	23.2	24.3
	48	4.2	5.4	6.7	7.9	9.1	10.4	11.6	12.8	14	15.3	16.5	17.7	18.9	20.1	21.4	22.6	23.8
	49	4.6	5.8	7.1	8.3	9.6	10.8	12	13.3	14.5	15.8	17	18.3	19.5	20.7	22	23.2	24.4
	50	4.9	6.2	7.5	8.7	10	11.3	12.5	13.8	15	16.3	17.6	18.8	20.1	21.3	22.6	23.8

For values outside the range of this table, you can use the following formula:

P = -16.6999 - 0.0101059 * T + 0.00116512 * T² + 0.173354 * T * V + 4.24267 * V - 0.0684226 * V²

where

• P = Pressure needed (psi)
• T = Temperature of keg in °F
• V = Volumes of CO2 desired

Calculating length of beer line

Once you have established the CO2 pressure on your keg, you can determine what length of beer line you need to balance the system. The basic premise is that we need to drop nearly all the pressure between the keg and the faucet, leaving 1 psi to actually get the beer to come out. The formula for calculating the line length is:

L = P - (H * .5) - 1
     R

where

• L = length of beer line in feet
• P = pressure set on regulator gauge
• H = Total height from the center of the keg to faucet in feet
• R = Resistance of line from the following Resistance Table
• 1 = this is the residual pressure remaining at the faucet ^*

^* If you need a higher dispensing pressure to increase the dispense rate, use 2 instead of 1.

This formula determines what line size & length to use to drop all but 1 psi of pressure, leaving just enough to dispense the beer.

 

Beer Line Resistance Table
Line Type	Avg Resistance	Volume (ml per ft)
3/16" I.D. plastic beer line	2.7	4.9
1/4" I.D. plastic beer line	0.7	9.9
5/16" I.D. plastic beer line	0.17	22.2
3/8" I.D. plastic beer line	0.11	22.2
1/2" I.D. plastic beer line	0.025	39.4
1/4" O.D. Stainless Beverage Tubing	2	4.9
5/16" O.D. Stainless Beverage Tubing	0.5	9.9
3/8" O.D. Stainless Beverage Tubing	0.2	22.2

Let's figure out a few examples:

Example 1

• Faucet is 2 ft above the center of the keg
• Desired volumes of CO2 is 2.4
• Temperature of keg is 40°F
• We're using 3/16" id plastic beer line, with a pressure drop of 2.7 psi per ft.

Looking in the carbonation chart above, the regulator setting should be 11.2 psi for 2.4 volumes CO2.

The formula is:

L = P - (H * .5) - 1      R

=

11.2 - (2 * .5) - 1      2.7

=

11.2 - 2      2.7

=

9.2   2.7

=

3.41 ft.

This means that a 3/16" line of 3 feet 5 inches will drop enough pressure so that the keg will stay at the desired carbonation level, yet the dispensing pressure will be low enough (around 1 psi) such that it will not foam.

Example 2

Suppose your system is in the basement and you need to get it upstairs.

• Faucet is 12 ft above the center of the keg and a few feet to the side.
• Desired volumes of CO2 is 2.8
• Temperature of keg is 44°F
• We're using 3/16" id plastic beer line, with a pressure drop of 2.7 psi per ft.

Looking in the carbonation chart above, the regulator setting is 16.7 psi.

The formula is:

L = P - (H * .5) - 1      R

=

16.7 - (12 * .5) - 1    2.7

=

16.7 - 7  2.7

=

9.7 2.7

=

3.6 ft.

Oops! 3.6 ft of tubing won't quite stretch up to the faucets, so let's try again, but this time let's use 1/4" id tubing with a pressure drop of .7 psi / ft.

L = P - (H * .5) - 1      R

=

16.7 - (12 * .5) - 1   .7

=

16.7 - 7  .7

=

9.7  .7

=

13.85 ft.

That's better. The 1/4" line has about 1/4 th the resistance, so we need about 4 times the length.

Example 3

Suppose you want to feed two taps from the same keg. Your system is in the basement, one tap is in the basement about 10 feet away, and the other is upstairs. You will need to tee the line at the keg, and treat each line separately, as though it was the only line on the keg. Of course, if you are trying to dispense from both at the same time you may not have the desired results.

• Desired volumes of CO2 is 2.2
• Temperature of keg is 46°F
• Faucet 1 is 12 ft above the center of the keg, and a few feet to the side.
• Faucet 2 is only 1 ft above the center of the keg, but is about 10 feet away.

Looking in the chart above, the regulator setting is 11.8 psi.

The formula for faucet 1 is:

This is not long enough to reach the faucet, so we need to use some larger line. Notice that we need to drop 4.8 psi over the length of the tubing (leaving 1 psi at the faucet). We can use 5/16 ID to drop most of it, then finish with 1/4 or 3/16 ID to drop the rest. Let's say we will use 14 ft of 5/16 ID to reach the faucet, which will drop 2.38 psi, leaving 2.42 remaining. Approximately 10 1/2" of 3/16 ID will handle that (2.42 / 2.7).

The formula for faucet 2 is:

Again this is not long enough since the faucet is 10 ft from the keg. Let's first use 10 feet of 1/4 ID tubing to get to the faucet. This will drop 10 * .7 or 7 psi, leaving 8.2. So we can now step down to 3/16" ID tubing and use 3 feet to finish it (8.2 / 2.7 = 3).

So for this example, we will put a Tee at the keg, use 14 ft of 5/16" ID followed by 10 1/2" of 3/16" ID to get to the faucet upstairs, and then use 10 ft of 1/4" ID followed by 3 ft of 3/16" ID for the faucet downstairs.

Summary

It really is not too difficult to set up a draft system that is balanced. Of course, once you tune your system to a specific temperature, pressure, and volumes CO2 it will not be tuned if you change any of them. So you need to determine the combination that give satisfactory results for most of your beers. Alternatively, you could have multiple taps at the same location that are each tuned separately. This works best if you have a CO2 manifold in your cold storage that allows you to regulate pressure to different kegs.

Troubleshooting

Here are some things to check when you are having problems with your beer. They were copied from one of the web sites mentioned above for preservation. I don't know how many times I've found info on the web that I bookmarked, then went back to a year later only to get a 404 error - file not found. So I've begun taking the liberty of copying such info and presenting it on this site for preservation. This site will not die unless the HBD dies (or me). Hopefully Pat will leave the HBD site in good hands in his will.

Cloudy Beer

Causes of hazy or cloudy draft beer	Required Correction
Over chilling of the beer keg or beer lines.	Beer should be stored at 36°F. to 40°F. Excessive low temperatures may cause hazy, cloudy beer, particularly when the beer is kept cold for a long time. Make sure the beer lines are thoroughly cleaned and then raise the temperature of the beer slightly.
Faucet is not being opened quickly and fully	Be sure to open the faucet completely and quickly.
Faucet is damages or dirty and will not open for full flow due to damages or warn faucet coupling washer or shaft seals or contamination build up.	Disassemble the faucet and check seals. Scour faucet internal metal parts till they are smooth and clean.
Contaminated air source	Switch to a CO2 or other gas system. Or, always have your compressor inlet drawing fresh clean outside air. Be sure to have a hair felt filter on the inlet as well as an inline charcoal filter in the outlet line.
Defective Thomas Valves or Tongue Vents in the keg coupler.	Bacteria may grow as a result of dirty or defective check valves in the coupler. Check and replace all vents and thoroughly clean the air lines. Replace if necessary.
Yeast growth or other obstruction in the faucet.	Clean faucet with a good brush daily. Scour all internal parts at least once a week.
Moisture in the air system.	A moisture trap must be installed in the Pre-Cooler and drained daily.

Flat Beer

Flat beer is when your draft beer has a foamy head which disappears quickly or the beer lacks the usual zesty flavor of brewery fresh beer.

Foul Beer

Off-taste beer is often bitter and bitey, sometimes completely lacking in flavor and zest. The beer may also have an oily or foul order with a very unpleasant taste.

Sour Beer

The beer has a yeasty or moldy taste.

Wild Beer

Wild beer is a beer that is all or mostly foam when it is drawn.

Before all else, remember your beer system had to be set up properly for pressure and line balance. This trouble shooting page is for systems that were set up and working properly and have gone astray.