CO2 bubbles in serving line

[henchman24]

I have been having this issue for a couple months and I'm now at a complete loss.

Lately with my kegerator, every time I pour a glass the CO2 comes out of suspension and forms bubbles in the lines (little bubbles form immediately and eventually gather into bigger bubbles). I'm at high altitude (over 6,000') so I have to have the pressures ~3 psi over what you'd normally see at sea level. I normally have the kegerator set for 34 degrees (though I have toyed with that temperature trying to find a solution, but it is back at that temp and has been for weeks). I have ~3-4 taps (depending on what I've brewed lately) shooting for 3.4 volumes (~21 psi at my altitude) and another ~3-4 taps shooting for 2.5 volumes (~13psi at my altitude). I always use the set it and forget it method of carbonating my beer. There was a point where some might have gotten over carbonated (don't know what happened, but both sides went 3-4 psi high for a couple weeks), but a newly force carbonated beer is having the same issue and there was no pressure rise (held steady at 21 psi).

The issues has been happening on both pressures.

Solutions that I have tried:

1. new 3/16 lines at various lengths (8-14' on the low pressure 14-19 at the high pressure)
2. installed a fan and new insulation to make sure the taps were roughly the same temperature (poured beer temperature is almost always <35)
3. re routed all lines to have a gradual upslope to push the bubbles towards the shank (only moderately successful)
4. new o-rings in all the kegs and all are using keg lube (I can't find any leaks)
5. re-carbonating (3x)... released all pressure for 4 days and re-carbed (newest beer hasn't had this happen)
6. lowered temperature to 33 and 32 degrees (this was early and the kegs have been re-carbed since)

I can also pour as much beer as I want out in one continuous pour and the bubbles never go away.

Ideas? I might try re-carbing again, but I don't really know what good that will do.

 

[GilSwillBasementBrews]

Usually what you describe is due to gas leaking from the headspace of keg into the liquid line. I know you replaced o-rings and used lube so unlikely but it's usually caused by a bad oring under the liquid out diptube. Could also be caused by pinhole in the diptube itself. That's where I'd start but sounds like you already got that covered so I'm at a loss.

 

[henchman24]

Thanks! I haven't checked the diptubes (didn't even think of that), but I can't see 6 of them all developing holes suddenly. It can't hurt to check though.

 

[opercularia]

Why are you carbing 3 psi more? The regulator is referenced to atmospheric pressure (regardless of altitude). You are pouring to atmospheric pressure. Go with standard pressures. You're probably over-carbing.

 

[mongoose33]

Why are you carbing 3 psi more? The regulator is referenced to atmospheric pressure (regardless of altitude). You are pouring to atmospheric pressure. Go with standard pressures. You're probably over-carbing.

I had that problem, tried several things to deal with it (including 3/16 tubing), and in the end, I was overcarbing.

 

[laredo7mm]

Why are you carbing 3 psi more? The regulator is referenced to atmospheric pressure (regardless of altitude). You are pouring to atmospheric pressure. Go with standard pressures. You're probably over-carbing.

At sea level atmospheric pressure is 14.7 psi. At 6000 feet it is 11.8 psi. Since the gauge is measuring the difference between the keg and atmosphere then the keg at 6000 feet would need to be set about 3 psi higher than the keg at sea level for the beers to have the same carbonation volumes.

 

[doug293cz]

At sea level atmospheric pressure is 14.7 psi. At 6000 feet it is 11.8 psi. Since the gauge is measuring the difference between the keg and atmosphere then the keg at 6000 feet would need to be set about 3 psi higher than the keg at sea level for the beers to have the same carbonation volumes.

Correct, but you left out the reason why.

Carbonation depends on the total (or absolute) pressure of the CO2, which is equal to gauge pressure plus atmospheric pressure. So, at sea level and 38&#730;F, it takes 11.2 psi of gauge pressure to get 2.5 volumes of carb. This is the same as 11.2 + 14.7 = 25.9 psi of absolute pressure. So, it takes 25.9 psi of absolute pressure to get 2.5 volumes at 38&#730;F. If you are at high altitude, and atmospheric pressure is only 11.8 psi, then to get your 2.5 volumes you need 25.9 - 11.8 = 14.1 psi of gauge pressure

 

[henchman24]

Yep atmospheric pressure is lower at high altitude, so higher pressures are needed to compensate.

Over the weekend I built a pressure gauge to check for variance between kegs and what their actual pressures were. I think I solved most of the issue. On the higher volume side the pressures varied from 22-25 psi and on the lower volume side were 15-17 psi. I did the sticky thread trick for getting rid of over carbonated kegs, and most are working well now (and at the ~13 and ~21 psi). I think there might be some sort of regulator issue as the pressures keep wanting to creep up.

 

[opercularia]

Correct, but you left out the reason why.

Carbonation depends on the total (or absolute) pressure of the CO2, which is equal to gauge pressure plus atmospheric pressure. So, at sea level and 38&#730;F, it takes 11.2 psi of gauge pressure to get 2.5 volumes of carb. This is the same as 11.2 + 14.7 = 25.9 psi of absolute pressure. So, it takes 25.9 psi of absolute pressure to get 2.5 volumes at 38&#730;F. If you are at high altitude, and atmospheric pressure is only 11.8 psi, then to get your 2.5 volumes you need 25.9 - 11.8 = 14.1 psi of gauge pressure

Don't know the science behind it, but my gut feeling is that if you carb to the number of volumes appropriate for sea level, you will be over-carbed at a higher altitude. With exposure to the lesser pressure at higher altitude, the CO2 will try to escape faster i.e. be over-carbed. Am I completely out to lunch?

 

[doug293cz]

Don't know the science behind it, but my gut feeling is that if you carb to the number of volumes appropriate for sea level, you will be over-carbed at a higher altitude. With exposure to the lesser pressure at higher altitude, the CO2 will try to escape faster i.e. be over-carbed. Am I completely out to lunch?

Yeah, you're out to lunch. I understand why your gut feeling seems reasonable, but I do know the science, and your gut is incorrect. The rate of CO2 absorption or desorption ("escape") is dependent on the difference between the partial pressure of CO2 in the surrounding atmosphere and the equilibrium partial pressure for the carb level of the beer, and the temperature (which determines the equilibrium partial pressure.) At equilibrium, the amount of CO2 entering solution is equal to the amount of CO2 leaving solution, so there is no change in the amount of CO2 in solution.

As stated in a previous post, CO2 partial pressures (not gauge pressures) for typical carbonation, at typical serving temps, are around 25 psi.

The CO2 percentage in the open atmosphere is about 0.04%, so at sea level, the partial pressure of CO2 is 14.7 * 0.0004 = 0.006 psi. If at high elevation where the atmospheric pressure is 11.8 psi, then the CO2 partial pressure is 11.8 * 0.0004 = 0.0047 psi. Now the rate of CO2 desorption (escape) is equal to the equilibrium partial pressure (25 psi or so if the beer is cold) and the atmospheric CO2 partial pressure. The difference between (25 - 0.006) and (25 - 0.0047) is insignificant. The uncertainties of the carb level and beer temp are orders of magnitude more than the difference in partial pressure deltas.

Thus, altitude makes no significant difference in the rate of CO2 loss from served beer.

Brew on

 

[opercularia]

Thanks. Guess I'd better save my gut for ingestion, not thinking.

 

[CamG]

Usually what you describe is due to gas leaking from the headspace of keg into the liquid line. I know you replaced o-rings and used lube so unlikely but it's usually caused by a bad oring under the liquid out diptube. Could also be caused by pinhole in the diptube itself. That's where I'd start but sounds like you already got that covered so I'm at a loss.

Thank you !
I had the same problem as the OP for three weeks.
I thought I did everything. I de-carbed, changed the O-rings on gas in and beer out posts, de-carbed again, changed the serving line, de-carbed again, I was ready to give up. Did I mention how many times I de-carbed this poor beer ?

I figured it was an infection and was so fed up i was ready to dump 3/4 of a keg.
I thought I would ask here before dumping so I took pictures of the beer line and was about to ask for some advice and low and behold I found this thread.

I pulled the dip tube and replaced it with another from a clean keg and it's flowing perfectly. I will pick up some dip tube O-rings tomorrow to have on hand.

Thank you again GilSwillBasementBrews!

Sorry henchman24 I didn't mean to hi-jack your thread... just really needed to say Thank You to GilSwillBasementBrews and also hope that someone else benefits from this solution by reading this in the future.
I really hope you get your CO2 problem solved... Good Luck

 

[BeardedBrews]

Oh man! I've been fighting against bubble accumulation in my serving lines (and a big slug of foam in the first pint of a pour) for MONTHS. I figured it was just my messy tubing storage, and had just been dumping the foam. It never occurred to me that I could possibly fix this problem with an O-Ring change.

<Fingers Crossed>

 

[CamG]

Oh man! I've been fighting against bubble accumulation in my serving lines (and a big slug of foam in the first pint of a pour) for MONTHS. I figured it was just my messy tubing storage, and had just been dumping the foam. It never occurred to me that I could possibly fix this problem with an O-Ring change.

<Fingers Crossed>

Hi BeardedBrews,
Make sure you check the O-ring on the dip tube as well and not just the quick connect post. This was what my problem was.

 

[henchman24]

No worries CamG. Glad your's got solved!

My issues were/are based on the regulator from what I can tell. This most recent de-carb and rebuilding regulators (I think this was my main issue) has solved mine so far. Fingers crossed.