Purging a corny keg

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Dave T

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Doing my first kegging expedition today - air and new taps all set up, ready to go. After I fill the keg, I know I will need to purge the air, how is this done? The CO2 goes into the short tube side, definitely don’t want to purge from the other side, so do I connect the CO2, disconnect and release, and repeat a couple times?

Or should I just suck it up and rig another air line for a long tube CO2 connection?

Thanks

Dave
 
Connect the co2. Fill your keg and then turn the gas off at the regulator and vent. Do this a few times. Don't do what I just did and forget to close the pressure release. It squirted beer everywhere.
 
I fill the keg completely with starsan solution and then use CO2 to push it out into a bucket through the liquid out connection to which I have attached a hose.

If you want to sanitize two kegs you can then push the starsan solution out of the first keg into a second one with C02 by connecting both keg's liquid outs with a tube. You have to vent the gas intake connection on the second keg or if you have a pressure release valve on the second keg's lid you can use that to vent periodically.

You can then use C02 to push the starsan out of the second keg into a bucket and use it or save it.
 
Using sanitizer and pushing it out with CO2 will use up less CO2 than completely CO2 filling an empty keg and purging it several times to ensure the O2 is out. You will still need to purge the headspace couple of times if using a filled keg of sanitizer, but you will use a lot less CO2.


Rev.
 
To purge the headspace of your keg, you'd normally put a burst of CO2 into the short dip tube (the gas in post) and release/vent using the Pressure Release Valve (PRV). Some kegs don't have manual PRV's though (they look like the picture below). WIth these, you need to put in a burst of CO2, remove the CO2 disconnect, push the pin in the gas in post to vent the headspace, then repeat the whole thing a couple more times.
ulid.jpg
 
Using high pressure (30psi) to do the purge will remove more O2.

Also it is good to use 30psi to seat the lid. I have some kegs that will leak if I try to seat with serving pressure.
 
Usually can purge an empty sanitized keg with co2 just prior to filling. Don't be sold on filling, emptying, and repeating. Co2 has a higher density than the other gases found in the air, which typically makes Co2 heavier than air. So if you allow a few seconds of Co2 to fill your empty corny, while you fill it with beer, that denser layer of Co2 will remain on top of the beer as it fills up the corny. Worried about any head-space after corny is full? Just release the PRV to let out some bursts, and you'll be good to go.

Don't over think or over complicate it.
 
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wmubronco said:
Don't be sold on filling, emptying, and repeating. Co2 has a higher density than the other gases found in the air, which typically makes Co2 heavier than air. So if you allow a few seconds of Co2 to fill your empty corny, while you fill it with beer, that denser layer of Co2 will remain on top of the beer as it fills up the corny.
Click to expand...

Here we go again. This information is plain wrong. Stratification doesn't occur in seconds. If it did we would all be dead on planet Earth as all CO2 would settle to sea level and the O2 would be above and out of reach of our lungs. It doesn't work that way.


Rev.
 
Rev2010 said:
Here we go again. This information is plain wrong. Stratification doesn't occur in seconds. If it did we would all be dead on planet Earth as all CO2 would settle to sea level and the O2 would be above and out of reach of our lungs. It doesn't work that way.


Rev.
Click to expand...
Yet when you keep it in the confined space (e.g. bottom of a corny keg), you're creating a cavity for it to remain as a "layer." Am I wrong? Do a couple bursts of co2 into the corny without the lid on it, fill it with beer, then when it reaches the top, give it a good sniff.... what's the non-oxygen gas that burns as you inhale?

All you're trying to do it create a barrier of Co2 that'll remain on top of the beer as you fill the corny.... and when it's full, you can put the lid on and then add a few more "purging" bursts to clear out any remaining oxygen, while using the PRV.....

So that 5 gallons of beer you just did with the above process is indeed "oxygen-free" and don't have to worry about wasting unnecessary co2.

All I'm saying...
 
wmubronco said:
Yet when you keep it in the confined space (e.g. bottom of a corny keg), you're creating a cavity for it to remain as a "layer." Am I wrong?
Click to expand...

Yes, you are wrong. Why don't people immediately asphyxiate when entering underground caves? Gas stratification and atmospheric stratification is a rather complex science. It's not so clear cut as "one is heavier than the other" - and density is more of what we're speaking of. Gases mix and take time and pressure to separate and stratify. Do that first "burst" you quote and tell me if you get 100% clean air that doesn't also burn your nose. The gases mix.

Best way is to fill the keg with liquid so that it displaces all the gas except for the headspace. You then purge that a few times and that will leave the least amount of air in the keg and waste the least amount of CO2 in your tank.


Rev.
 
When you purge after filling a keg with beer, do you need to turn off the gas at the regulator or the tank before venting with the pressure relief value?
 
njohnsoncs said:
When you purge after filling a keg with beer, do you need to turn off the gas at the regulator or the tank before venting with the pressure relief value?
Click to expand...

Edit: posted before I finished writing.
No. You don't need to.
You can turn it off, vent, turn it on again and off again, vent, on and off again, vent, then on again to seal the lid.
Or you can just leave it on which uses a bit more gas.
 
Thank you. I noticed after I kegged that I have a couple lids with the relief - how do I open the relief, just stick something in one of the holes? Of course, I didn’t use that one so I went with the manual method at 30psi...
 
It's a minor point really. For a full keg, there's not much to purge off. Personally, I keep the gas on with a few short vent bursts.
Either way works.

EDIT: I may not be fully tracking here. I'm assuming a full keg with a PRV lid. Without a PRV, then yes turn the gas off each time.
 
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"It takes time for the gases to diffuse" I dont even sweat it this much. I just rack into a sanitized kegs and purge it 3-4 times. Maybe that uses like 1 gallon of co2 instead of 5. If you were obsessed about o2 and lodo why not ferment in a keg and do a closed transfer.
 
Rev2010 said:
Best way is to fill the keg with liquid so that it displaces all the gas except for the headspace. You then purge that a few times and that will leave the least amount of air in the keg and waste the least amount of CO2 in your tank.

Rev.
Click to expand...

This is what I was trying to convey. I do not doubt Co2 is displaced. It is mixed with the oxygen in the empty space. Yes, filling with liquid to push any gases that may be mixed with the minimal Co2 that was put in at the start, followed by leaving minimal headspace for when you seal the keg. Then do some small amounts of Co2 to purge whatever remaining oxygen may be left in there.

Problem solved.
 
TallDan said:
Yes. Stop repeating this.

Click to expand...


Really? Show me the video depicting oxygen in a cylinder (corny key) and the rate (speed at which Co2 diffuses into oxygen), proves my "layer" theory wrong.

Chlorophyll??? More like borophyll! Bromine has a way more different molecule makeup than Co2, so of course it'll diffuse at a different rate.

Would the phrase "diffused region of Co2 into oxygen above liquid (beer)" been more appropriate?
 
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Cantina De Jefe said:
"It takes time for the gases to diffuse" I dont even sweat it this much. I just rack into a sanitized kegs and purge it 3-4 times. Maybe that uses like 1 gallon of co2 instead of 5. If you were obsessed about o2 and lodo why not ferment in a keg and do a closed transfer.
Click to expand...

Been using this logic ever since I started kegging.
 
Some of you might need to start a new thread if you want to argue about gas diffusion and empty keg purging. Someone new to kegging has asked a specific question (how to vent the headspace of a keg that's already full of beer) and the off-topic discussion is dominating. Try to stick to the topic.

Dave T said:
Thank you. I noticed after I kegged that I have a couple lids with the relief - how do I open the relief, just stick something in one of the holes? Of course, I didn’t use that one so I went with the manual method at 30psi...
Click to expand...

The picture I posted in post #6 has a PRV that can't be manually released. It's only there to vent if the keg builds up too much pressure to prevent it from exploding. They are a bit of a PITA. To vent, you need to remove the gas disconnect and push in the pin in the gas post (use a small screwdriver or similar). Make sure the liquid level isn't above the end of the gas dip tube!
 
IMG_1451.JPG


In the future, it is probably better to remove O2 by filling the keg with liquid. Then remove the liquid with CO2. Then replace the CO2 with beer (close transfer). Much less CO2 will be used than purging.
 
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Gnomebrewer said:
Someone new to kegging has asked a specific question (how to vent the headspace of a keg that's already full of beer) and the off-topic discussion is dominating. Try to stick to the topic.
Click to expand...

With all due respect, his question was already answered several times. And I beg to differ the discussion has gone off topic as someone posted bad advice to our newbie kegging friend and some of us that know science better have been correcting said individual. There's nothing wrong with trying to help others follow best practices. I for one am done arguing it. I still say to the OP, fill the keg with sanitizer, purge the headspace a couple of times, and push out the liquid out with CO2 for the best oxygen purging. It's what the vast majority of us do and also uses the least amount of CO2.


Rev.
 
Gnomebrewer said:
Some of you might need to start a new thread if you want to argue about gas diffusion and empty keg purging. Someone new to kegging has asked a specific question (how to vent the headspace of a keg that's already full of beer) and the off-topic discussion is dominating. Try to stick to the topic.



The picture I posted in post #6 has a PRV that can't be manually released. It's only there to vent if the keg builds up too much pressure to prevent it from exploding. They are a bit of a PITA. To vent, you need to remove the gas disconnect and push in the pin in the gas post (use a small screwdriver or similar). Make sure the liquid level isn't above the end of the gas dip tube!
Click to expand...
Man, I wish one of my posts would ignite this much debate. WE MUST DIGRESS!!!RABBLE RABBLE!!
 
Cantina De Jefe said:
Man, I wish one of my posts would ignite this much debate. WE MUST DIGRESS!!!RABBLE RABBLE!!
Click to expand...

Apart from the side issue of the gas "layering" myth, I must admit there seems to be quite a bit of opinion regarding the simple task of purging the small bit of space in a full keg.... It's really not that complicated.
 
SEndorf said:
Apart from the side issue of the gas "layering" myth, I must admit there seems to be quite a bit of opinion regarding the simple task of purging the small bit of space in a full keg.... It's really not that complicated.
Click to expand...
It really comes down to what style, how long you intend to set it down for, and how anal or lazy/cheap you want to be. My beer always tastes best at the end of the 2nd keg anyways. If a few thousand ppm o2 was so detrimental i would be tasting skunk-a-lotta-piss-on-my-wet-cardboard ale. I mean someday i would like to do spunding and closed transfers but for now i dont want to increase my usage by 1/3. I already had 1 tank leak out this year as it is.
 
How old do you need to keep a keg before you notice a downturn due to oxygen? I haven't really worried about oxygen exposure, but maybe I should.

When I keg, I take the top completely off of the fermentation bucket during the process, so it's exposed to oxygen. I rack to a keg, which had been sprayed with Star San. When I'm done, I put on the lid, add ~30 psi of CO2, then leave it for a couple days. I purged a few kegs after adding CO2, but there have been at least a dozen kegs where I didn't purge at all. So I guess there's some oxygen in the headspace, but I haven't really noticed any skunked beers after the keg has been sitting for 1-2 months.
 
Carolina_Matt said:
How old do you need to keep a keg before you notice a downturn due to oxygen? I haven't really worried about oxygen exposure, but maybe I should.

When I keg, I take the top completely off of the fermentation bucket during the process, so it's exposed to oxygen. I rack to a keg, which had been sprayed with Star San. When I'm done, I put on the lid, add ~30 psi of CO2, then leave it for a couple days. I purged a few kegs after adding CO2, but there have been at least a dozen kegs where I didn't purge at all. So I guess there's some oxygen in the headspace, but I haven't really noticed any skunked beers after the keg has been sitting for 1-2 months.
Click to expand...
I believe skunking is caused by exposure to light, not oxygen.
 
Actually the atmosphere is stratified into two main layers; heterogeneous and homogeneous. I watched the video that was attached. Clearly there are two layers and the narrator states that "over time" and after 1/2 hour the layers have combined. So clearly layers are formed, isn't it just a question of how long the CO2 and O2 layers last and the environment that the gasses are in? For home brewing purposes let's say the time is similar for O2 and CO2 it doesn't take 1/2 to rack or transfer so isn't it possible that there are some benefits to the blanket theory?
 
ApolloSimcoe said:
Actually the atmosphere is stratified into two main layers; heterogeneous and homogeneous. I watched the video that was attached. Clearly there are two layers and the narrator states that "over time" and after 1/2 hour the layers have combined. So clearly layers are formed, isn't it just a question of how long the CO2 and O2 layers last and the environment that the gasses are in? For home brewing purposes let's say the time is similar for O2 and CO2 it doesn't take 1/2 to rack or transfer so isn't it possible that there are some benefits to the blanket theory?
Click to expand...
In the video, the layers are formed artificially, and the gasses are kept as still as possible to illustrate the point.

The amount of time is going to depend on the difference in density of the gasses and any turbulence in the air. When racking, there is going to be a fair amount of turbulence as air is being pulled into the fermenter as the beer is drained, and it's being pushed out as beer is filling the keg.

Really it's a question of "good enough". Some people don't purge their kegs at all, don't even rack carefully, and that's good enough for them. Some are very concerned with "LODO" and go to what I would consider extreme measures to avoid any possible oxygen exposure. I'm somewhere in the middle.
 
funny that keg purging is just as polarizing as politics and the Patriots NFL
 
My corny has a relief valve in the center of the cover. I fill and add co2 then pull the valve three times. Wait about a minute pull three more times. Let it sit for three days in the kegerator at 38 degrees. Plug in the beer line pull the tap three times quickly and pour away.
 

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