So, prepping for my first kegging - purging O2 confusion - question

[Rev2010]

So I've done some searching online but some questions remain.

1. First question... I can't for the life of me understand something I've been reading and that is some people saying they CO2 purge the keg *before* filling. Wait what?? I mean, don't you have to open the lid anyway and use tubing to drain from your fermenter into the keg? So why CO2 purge the keg first?? Just seems quite strange

2. After I fill my keg, seal it up, and do the pressurize with CO2 and purge with the PRV to release any O2 a couple of times... do I keep the CO2 flowing or do I need to shut off the gas between purges? From what I've seen most keep the gas on yes?

3. Lastly, I've seen videos where they say the purging causes some beer to also spray out the PRV, well that sucks. What's the best way to deal with this? Thinking of cleaning off the keg top after purging I figure there must be a better way?

Any info you guys can provide would be extremely appreciated!


Rev.

 

[baseballsmitty]

A few comments based on what I do.

1) I end up pushing star San through my beer line using CO2, so in affect I am also purging the keg before filling. I think the idea is that CO2 is heavier that the outside air, so even though you take the lid off of the keg it will still be full of CO2 (and void of oxygen). This prevents the chance of oxygenating your beer during transfer into the keg.

2) I typically fill the keg and then turn off the CO2 before purging. This way I know when all of the CO2 has been purged. I repeat this process a few times before setting the CO2 pressure and leaving it until carbonation is finished.

3) The only time I've had this happen was when I was trying to quickly force carbonate the keg by pressurized it to ~50 psi and then shaking the crap out of it. Without the shaking I've never had anything spray out of the PRV.

Hope this helps.

 

[govner1]

So I've done some searching online but some questions remain.



1. First question... I can't for the life of me understand something I've been reading and that is some people saying they CO2 purge the keg *before* filling. Wait what?? I mean, don't you have to open the lid anyway and use tubing to drain from your fermenter into the keg? So why CO2 purge the keg first?? Just seems quite strange



2. After I fill my keg, seal it up, and do the pressurize with CO2 and purge with the PRV to release any O2 a couple of times... do I keep the CO2 flowing or do I need to shut off the gas between purges? From what I've seen most keep the gas on yes?



3. Lastly, I've seen videos where they say the purging causes some beer to also spray out the PRV, well that sucks. What's the best way to deal with this? Thinking of cleaning off the keg top after purging I figure there must be a better way?



Any info you guys can provide would be extremely appreciated!





Rev.

CO2 is denser than ambient air so that purging before filling from your carboy creates a blanket of CO2 to help prevent oxidation.
Keep the gas on as you seal and purge. No need to turn it off in between.


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[Tiber_Brew]

1. Yes, I would recommend purging with CO2 prior to filling the keg. Add a few gallons of sanitizer to your keg, shake it up, drain some out of the gas post, then drain the rest out of the liquid post by pushing it out with CO2 (you could use a picnic tap for this). This will also displace most if not all air with CO2. In my setup, I use CO2 pressure to fill the keg from my fermenter via the liquid post, so the top never comes off after sanitation and CO2 purge.

2. You can do either. I let the pressure build a bit between purges to get a higher velocity discharge.

3. That's really most likely if your beer is already carbonated. CO2 solubility is a function of pressure and temperature, so if you have a carbonated beer under 24 PSI at 65 deg F then you suddenly open the valve to release the gas, the pressure will decrease, thus decreasing the solubility of CO2 and breaking the gas out of the beer (causing lots of foam). If your beer is flat, you shouldn't have any issue with foam coming out of your PRV while purging gas (I know that's never happened to me in seven years of kegging).

TB

 

[Rev2010]

Thanks for the info guys, much appreciated!

*EDIT - one additional question. I just read this on another site, "In all circumstances, do not carbonate your beer - or pressurize your keg above 10 psi - with your product line/faucet assembly attached. Keep your product line *disconnected* until you are ready to serve your beer,"

Is that really necessary or can the liquid out remain attached the entire time? I'm ok with doing that, just wondering.


Rev.

 

[GilSwillBasementBrews]

I leave mine attached and carb over 10psi. My hard rootbeer sits around 30psi with serving line hooked up


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[Rev2010]

OK, one more, if I decided to be on the safe side and carb the keg without the liquid line being connecting would it be fine to just sanitize the lines on the day I fill the keg and attach it to the gas, or would I really need to sanitize the line right before the beer is ready to flow? I'd imagine the system is closed enough that sanitizing the line those two weeks before when I keg the beer should be fine no? And would what little trace of StarSan that's in the lines after it's done running through be ok to sit for two weeks?

So sorry for the dumb questions. I just would prefer to do all the cleaning and sanitizing on one day, and since the keg will take almost two weeks to carb I want to be sure it's ok to do that all on kegging day and not have to do a split part to the day I'm ready to drink.


Rev.

 

[peterj]

To go back to your first questions, I personally think it's a waste of time and CO2 to purge the air out before you fill your keg. The beer will be exposed to air for maybe 5 minutes while you rack it. There's no way it will pick up even close to a significant amount of oxygen in that short amount of time unless you're putting the end of the siphon tube at the top of the keg and letting it fall to the bottom or something. Then after the 5 minutes or so it takes to rack it you're purging all of the air out anyway.

I always fill the headspace with CO2 at about 30 psi, turn the valve off, pull the PRV, turn the CO2 back on and repeat. I usually do this about 3 or 4 times. You could do it either way I guess, I just prefer to turn it off in between because I guess it feels more precise to me.

And like Tiber_Brew said, it shouldn't foam out of the valve unless it's already carbonated or something. Or maybe if you over fill the keg. I've never had it happen to me though.

As for your last question, I wouldn't listen to whatever source you got that from. You need to put the regulator at the correct pressure for whatever temperature the beer is at to get your desired level of carbonation. That is usually going to be 10 psi or higher. Here's a calculator to determine the psi: http://www.brewersfriend.com/keg-carbonation-calculator/.

And you can carbonate with the beer line attached, though I've noticed the CO2 doesn't diffuse as well into the line. I usually don't attach the line until I'm reasonably sure it's carbonated. It shouldn't be too hard to just fill it with starsan on the day you want to tap the keg. Or I guess you could store it full of starsan and then drain it right before hooking it up. I wouldn't leave it empty for 2 weeks and then hook it up without sanitizing it again. It might be fine, but I personally wouldn't take the chance.

 

[Rev2010]

To go back to your first questions, I personally think it's a waste of time and CO2 to purge the air out before you fill your keg.

I completely agree, I've never heard of purging air out of bottles and each of mine would sit with a cap simply sitting on top until all bottles were filled and I started crimping the caps with my bench capper. Never once had a problem. Adding to that, the idea that CO2 will just sit there in the keg while filling seems a bit of a fallacy. While CO2 is heavier than O2 we're breathing in a mix of of gases right now. We're not all standing in a several mile thick band of CO2. I would imagine CO2 in an open keg would blend and dissipate into the surrounding outside air anyway.

I always fill the headspace with CO2 at about 30 psi, turn the valve off, pull the PRV, turn the CO2 back on and repeat. I usually do this about 3 or 4 times. You could do it either way I guess, I just prefer to turn it off in between because I guess it feels more precise to me.

That's exactly what I was planning to do, 30 psi three times with shutting off the flow, just so I know it's purged before going again. I also read it's good to give it one final 30 psi charge before adjusting to your carbing psi just to ensure the lid it firmly sealed so I figured I'd do that too.

And you can carbonate with the beer line attached, though I've noticed the CO2 doesn't diffuse as well into the line. I usually don't attach the line until I'm reasonably sure it's carbonated.

It shouldn't be too hard to just fill it with starsan on the day you want to tap the keg.

Yeah I was wondering about that and since it will be my very first kegging attempt was figuring I better be safe and not connect the liquid out connect. I'll just use my hand pump cleaner bottle with some StarSan on the day of connecting it to start drinking. Thanks so much again, I think I've now worked out the curious gremlins in my brain


Rev.

 

[peterj]

I completely agree, I've never heard of purging air out of bottles and each of mine would sit with a cap simply sitting on top until all bottles were filled and I started crimping the caps with my bench capper. Never once had a problem. Adding to that, the idea that CO2 will just sit there in the keg while filling seems a bit of a fallacy. While CO2 is heavier than O2 we're breathing in a mix of of gases right now. We're not all standing in a several mile thick band of CO2. I would imagine CO2 in an open keg would blend and dissipate into the surrounding outside air anyway.



That's exactly what I was planning to do, 30 psi three times with shutting off the flow, just so I know it's purged before going again. I also read it's good to give it one final 30 psi charge before adjusting to your carbing psi just to ensure the lid it firmly sealed so I figured I'd do that too.





Yeah I was wondering about that and since it will be my very first kegging attempt was figuring I better be safe and not connect the liquid out connect. I'll just use my hand pump cleaner bottle with some StarSan on the day of connecting it to start drinking. Thanks so much again, I think I've now worked out the curious gremlins in my brain


Rev.

Yeah, the CO2 being "heavier than air" effect is somewhat of a myth. You may get some "blanketing" if your CO2 was in the fridge because the colder gas is denser than the room temp air but it still wouldn't be worth it. And if you're doing a completely closed system like Tiber_Brew described then it would work, but again I don't think it's worth it.

Glad I could help you out! Have fun kegging!