Co2 fill after kegging

[IslandLizard]

@IslandLizard - After reading that, I think I'll just stick to my usual pre-fill purge then 3x post fill headspace purge.

Rev.

You only need to do one of the 2 methods. Doing both IS wasting time and gas.
If you've got 5 gallons of beer, the headspace is small (~1/2 gallon) and it easily and quickly purged (3x at 30psi) with a relatively small amount of CO2, compared to a full pre-filling purge.

 

[Rev2010]

Right. Unless you're brewing under pressure with a spundling valve I just don't see the point in getting too intense. Youre getting oxygen in when you pull a sample, throw in dry hops, rack, etc. Definitely try to minimize, but there's a certain reality you have to accept unless it's completed closed-system.

Exactly. And from what I've read most descriptions of oxidation and its affect on flavor is a wet cardboard or sherry like taste. I've never once had those tastes in my beers. Again, not saying there's no merit, just that I think as homebrewers we really need to determine our own limits as to how far we'll go for diminishing returns.


Rev.

 

[Rev2010]

You only need to do one of the 2 methods. Doing both IS wasting time and gas.
If you've got 5 gallons of beer, the headspace is small (~1/2 gallon) and it easily and quickly purged (3x at 30psi) with a relatively small amount of CO2, compared to a full pre-filling purge.

Was just referring to the pre-fill process by removing the gas in and using a tube and all that. Just seems a lot more involved than my usual process.


Rev.

 

[IslandLizard]

Was just referring to the pre-fill process by removing the gas in and using a tube and all that. Just seems a lot more involved than my usual process.

Rev.

You mean pre-fill purging? Sure it is much more work than purging after filling. But if you only have 3-4 gallons of beer for a keg, proper pre-fill purging is the way or you'd need 5-10 gallons of CO2 or more to remove 90% of the air. Remember the less beer, the more air there is to "remove."

 

[doug293cz]

Curiously enough, using @Doug's graphs, the break-even point of the amount of CO2 needed between pre-purging a whole 5 gallon keg and only purging the headspace after filling* lays at around 4 gallons of beer. That means that break-even point is already reached at 80% fill level!

So if you have 4 gallons or less beer to fill a keg, you're better off pre-purging.

*This is to achieve a residual O2 level of around 1-2% (5-10% air) in the post-filling purge. The O2 (air) level in a pre-purged keg is almost nil.

Pre-purging:
Pre-purging is done by filling the keg all the way to the very top with Starsan (~5.5 gallons), then closing it up, followed by pushing as much Starsan out as possible using CO2.

To fill the now pre-purged keg with beer, do not remove the lid, but instead remove the gas post and the (short) dip tube. Feed a 1/4" OD hose through the threaded stub all the way to the bottom leaving a few inches to a foot sticking out. Fill the racking/siphon hose with beer before attaching to the 1/4" tubing. As the keg fills with beer, the CO2 will escape between the inside of the threaded stub and the 1/4" hose.

Even filling thru the gas post hole will expose the beer to air in the fermenter, unless you back fill the vacated volume in the fermenter with CO2 (or other inert gas.) The only way to avoid air exposure is to run a fully sealed, positive pressure system once primary fermentation is complete. Some people try to do that, and it certainly won't hurt anything. The question is: do we really need to do that? I've never seen reports of oxidation in finished beer that didn't involve splashing or over stirring the beer. Can anyone provide links to reports of oxidation that occurred when the normally recommended precautions for racking and packaging were followed?

For oxidation to occur, you have to get O2 into the beer. O2 will diffuse into still beer given enough time, but the amount of diffusion in half an hour or so will be minuscule. Agitation will cause O2 to diffuse in much faster, and so is to be avoided.

Brew on

 

[Jwin]

I just put a ball lock post on my spiedel. Purge the keg once at 10 psi then transfer via pressure while the keg sits on a scale and I hold the prv open.
Go in the liquid dip tube so little movement is happening.
Then purge twice once full.

It worked great, only had to clean a keg and a hose, and never picked up more than 5g.
Was as much about being lazy as o2
Tasted good to me!

 

[IslandLizard]

Even filling thru the gas post hole will expose the beer to air in the fermenter, unless you back fill the vacated volume in the fermenter with CO2 (or other inert gas.) The only way to avoid air exposure is to run a fully sealed, positive pressure system once primary fermentation is complete. Some people try to do that, and it certainly won't hurt anything. The question is: do we really need to do that? I've never seen reports of oxidation in finished beer that didn't involve splashing or over stirring the beer. Can anyone provide links to reports of oxidation that occurred when the normally recommended precautions for racking and packaging were followed?

For oxidation to occur, you have to get O2 into the beer. O2 will diffuse into still beer given enough time, but the amount of diffusion in half an hour or so will be minuscule. Agitation will cause O2 to diffuse in much faster, and so is to be avoided.

Brew on

Don't you think that amount of air/O2 that enters through the gas post is very minimal while working with it? Only a very small volume of air will get in when removing the post, inserting the skinny tubing and removing it after filling. No it's not perfectly 100% oxygen free, but damn close. One could back stream CO2 through the liquid tube while working to limit air entry even more.

The main point I tried to make was that at 80% fill level (or lower) you'd use less CO2 by pre-purging the keg before filling it with beer. While doing so, you'd expose that beer to less air and end up with a lower % of air/O2 in the gas mix in the headspace than with post-fill purging.

I've not seen this procedure outlined anywhere else. Is it necessary? I'd say leave that up to the individual.

 

[Peruvian802]

If gasses did stratify, we'd all die in our sleep from c02 poisoning.

I sleep on the top bunk. Just in case...

 

[Yooper]

The question is: do we really need to do that? I've never seen reports of oxidation in finished beer that didn't involve splashing or over stirring the beer. Can anyone provide links to reports of oxidation that occurred when the normally recommended precautions for racking and packaging were followed?

For oxidation to occur, you have to get O2 into the beer. O2 will diffuse into still beer given enough time, but the amount of diffusion in half an hour or so will be minuscule. Agitation will cause O2 to diffuse in much faster, and so is to be avoided.

Brew on

Well, the thing is, oxidation IS in most homebrewed beer, to one degree or another and this magnifies with age.

A classic example is a barley wine that is 3-4 years old. Signs of oxidation- sherry notes, prunes, etc- are actually part of the profile. A "big" high alcohol beer can really be nice with those notes, and those come from oxidation.

Most beers aren't drunk when they are that old, as oxidation is NOT a desired part of the profile. So, in a beer that has been well taken care of, and is being drunk before a year old may not show as many signs of oxidation but there well may be some, especially if the beer is stored at room temperature as warmer temperatures accelerate aging and those flavors.

With oxidation, several more subtle flavors occur before the classic "wet cardboard". First, hops and lighter flavors are muted a bit, as the beer starts to show signs of oxidation. In beers using dark/black malt, you may begin to notice a slight metallic taste that wasn't there before, as for some reason black malt tends to get that flavor of oxidation. I'm not sure why, so I"d have to research more into that, but several other noted BJCP judges have commented on that as well.

Then, the beer will actually start to darken a bit in color, say, from a light amber to copper. At that point, the madierization (the beginning of those "sherry" notes) starts and the beer can take on the madiera flavor, or sherry, and all the way up to brandy-like flavors as it worsens. The beer may also start to show signs of staling.

I've judged a lot of competitions as a BJCP judge, and the flaws I see most often are generally related to oxidation. Still, I've never once tasted a beer I would describe as "wet cardboard" or "moldy", the terms people on this forum says.

I've heard MANY people say, "Well, my beer isn't oxidized and I splashed it, etc". That's not true. It may not taste severely oxidized (the classic wet cardboard") but I bet if it was judged by a competent judge that some of the signs mentioned above are in that beer. It's not always unpleasant, especially in the early stages, but there is a note in there that will usually change with time and worsen.

 

[kevink]

One of the major points of home brewing (to me, anyway) is to control every part of the process as tightly as possible to make the highest quality beer. I'm going to continue purging my empty kegs and purge them again at least 8 times after I fill them. I'm going to purge the headspace in my fermenter after I open it to dry hop. I'm going to purge my lines prior to racking to a keg. If I cold crash, I'm going to connect CO2 to the blowoff so it doesn't suck air in. Hell, I might even start pulling a vacuum on my kegs prior to purging. I don't understand the "good enough" attitude or the RDWHAHB thing, but I guess not everyone takes it as seriously.

 

[Rev2010]

I don't understand the "good enough" attitude or the RDWHAHB thing, but I guess not everyone takes it as seriously.

It has little to do with "good enough" and more to do with reasonability. You can go ahead and use all that CO2 for every step of the process. I'm sure your beer will be perfect and pristine. The point is as *I* am doing it now (pre-fill keg purging and post fill headspace purging) my beers are coming out perfectly fine with no detectable ills from it. It's not a matter of, "Oh yeah there's a little off taste from the oxidation but it's good enough". There IS NONE. So why should I waste so much more CO2 to purge my fermenter headspace, transfer in a completely sealed system using CO2, purge 50x in 50 different ways, etc? I only have to make one trip a year to fill up my 2 CO2 tanks (I stop brewing late spring and through summer since house temps are too warm). If I strived for zero oxygen exposure I'd have to make plenty more trips or bring many more tanks.

Again, as I am doing it I don't notice any off tastes as a result of any oxidation. I've been beer connoisseuring for about 17 years now so I know my beer pretty well I'd say. Perhaps if I did want to do a barleywine and age it for years then for that beer I'd strive to eliminate O2 exposure as best as possible, but I'm not selling beers that will be sitting on shelves and I am not making any beers currently that will be vintaged so as it stands I'm happy with my process. It's not "good enough" it just provides the outcome I am seeking and works within my realm of reasonability for requirements of effort and cost.


Rev.

 

[kevink]

It has little to do with "good enough" and more to do with reasonability. You can go ahead and use all that CO2 for every step of the process. I'm sure your beer will be perfect and pristine. The point is as *I* am doing it now (pre-fill keg purging and post fill headspace purging) my beers are coming out perfectly fine with no detectable ills from it. It's not a matter of, "Oh yeah there's a little off taste from the oxidation but it's good enough". There IS NONE. So why should I waste so much more CO2 to purge my fermenter headspace, transfer in a completely sealed system using CO2, purge 50x in 50 different ways, etc? I only have to make one trip a year to fill up my 2 CO2 tanks (I stop brewing late spring and through summer since house temps are too warm). If I strived for zero oxygen exposure I'd have to make plenty more trips or bring many more tanks.

Again, as I am doing it I don't notice any off tastes as a result of any oxidation. I've been beer connoisseuring for about 17 years now so I know my beer pretty well I'd say. Perhaps if I did want to do a barleywine and age it for years then for that beer I'd strive to eliminate O2 exposure as best as possible, but I'm not selling beers that will be sitting on shelves and I am not making any beers currently that will be vintaged so as it stands I'm happy with my process. It's not "good enough" it just provides the outcome I am seeking and works within my realm of reasonability for requirements of effort and cost.


Rev.

Your kegging process is great and it's probably more than what most people do, but to do a little more (purge lines, purge fermenter headspace) you're probably only going to use 5% more CO2 (just a guess). You would probably see more benefit from temperature controlled fermentation if you don't already do that (you mentioned not brewing in certain times of the year due to warm house temps).

 

[Rev2010]

You would probably see more benefit from temperature controlled fermentation if you don't already do that (you mentioned not brewing in certain times of the year due to warm house temps).

I definitely would! I do brew a one off here and there over the warmer months since I can use my kegerator as a fermentation chamber - the temp can be set anywhere between 32-75. But once summer is over I ferment in my non-heated hallway which typically works great for keeping fermentation temps in the mid 60's.


Rev.

 

[Yooper]

One of the major points of home brewing (to me, anyway) is to control every part of the process as tightly as possible to make the highest quality beer. I'm going to continue purging my empty kegs and purge them again at least 8 times after I fill them. I'm going to purge the headspace in my fermenter after I open it to dry hop. I'm going to purge my lines prior to racking to a keg. If I cold crash, I'm going to connect CO2 to the blowoff so it doesn't suck air in. Hell, I might even start pulling a vacuum on my kegs prior to purging. I don't understand the "good enough" attitude or the RDWHAHB thing, but I guess not everyone takes it as seriously.

I don't know about that- "good enough" really is good enough, IF it's sound practice.

I don't keep IPAs around for 6 months, so if I didn't purge 8 times, and only 3, but still used sound brewing practices, I don't think it's an issue. The beer would be long gone before any oxidation flavors or stability issues would rear their ugly heads.

Sure, there are some brewers whose "good enough" isn't good enough for me, but I'm also not overly stressing about minor issues. Oxidation is a major issue, but not in a well made beer with good technique. Then, it can be considered a minor issue.

 

[doug293cz]

Don't you think that amount of air/O2 that enters through the gas post is very minimal while working with it? Only a very small volume of air will get in when removing the post, inserting the skinny tubing and removing it after filling. No it's not perfectly 100% oxygen free, but damn close. One could back stream CO2 through the liquid tube while working to limit air entry even more.

Yes, I think the amount of air entering the gas post hole would be minimal, but that's not the point of my previous comment.

You can't drain the fermenter without backfilling the vacated volume with some gas. Most of the time it is air. The the area exposed to air in the fermenter will be several times larger than the area exposed to air in an unpurged keg. The rate of O2 uptake by the beer will be proportional to the exposed area. Unless you backfill your fermenter with CO2 as it drains, you wiil pick up more O2 in the fermenter during draining, than in the keg during filling an unpurged keg. That was my point.

The main point I tried to make was that at 80% fill level (or lower) you'd use less CO2 by pre-purging the keg before filling it with beer. While doing so, you'd expose that beer to less air and end up with a lower % of air/O2 in the gas mix in the headspace than with post-fill purging.

That sounds like it makes sense, but unfortunately it's not correct. If you purge an empty keg at 15 psi, it will contain 49.5% of the original air and O2. The O2 concentration will be 49.5% of atmospheric concentration. After the keg is filled, the headspace will still contain 49.5% of the atmospheric O2 concentration, although it contains less total O2. The amount of O2 left after filling is the same amount of O2 that it would contain after a single purge cycle after filling without pre-purging (same volume @ same concentration.) But, you've used 5+ gal of CO2 instead of 1+ gallon (for your 80% full case.) You didn't gain anything from the extra 4 gallons of CO2 used, except less O2 exposure in the keg during the fill process (the actual benefit of which is being debated, no one's debating the theoretical benefit.) Perhaps the confusion is that the original calculations for the chart and table are based on concentrations of a particular gas, not the total amount of a particular gas.

Brew on

 

[doug293cz]

I added a clarification pertaining to the chart and table in post #3:

If the purged volume remains constant during all purges, then the "% of original remaining" refers to both total amount and concentration (total amount = concentration * volume.)

If the purged volume changes between purges, for example due to pre-fill and post-fill purges, then the "% of original remaining" refers only to concentration, not total amount. However, since the concentration is the same after a given number of purges, independent of the volume during the purges, the final result will be the same as if all purges were done post-fill, only if no air gets into the keg during the filling process. Any air that gets into the keg during the filling process will reduce the effectiveness of the pre-fill purges on reducing the final O2 content of the headspace.

Brew on

 

[IslandLizard]

Actually, it IS correct when pre-purging the way I had outlined before.

Pre-purging:
Pre-purging is done by filling the keg all the way to the very top with Starsan (~5.5 gallons), then closing it up, followed by pushing as much Starsan out as possible using CO2.

That method will first replace 100% of air with 100% Starsan (or close to that) and in succession replace the Starsan with 100% CO2. This requires around 5.5 gallons of CO2.

And as you described, simply gas-purging a keg full of air just with CO2 is very inefficient. It is also quite incomplete if not done at least 3 or 4 times. The cost is around 5.5 gallons per purge cycle, for a total of 16-22 gallons of CO2 or more.

 

[doug293cz]

Actually, it IS correct when pre-purging the way I had outlined before.



That method will first replace 100% of air with 100% Starsan (or close to that) and in succession replace the Starsan with 100% CO2. This requires around 5.5 gallons of CO2.

And as you described, simply gas-purging a keg full of air just with CO2 is very inefficient. It is also quite incomplete if not done at least 3 or 4 times. The cost is around 5.5 gallons per purge cycle, for a total of 16-22 gallons of CO2 or more.

Yeah, I forgot that you had previously mentioned the prefilling with liquid procedure. That method is more efficient of CO2 use than purging an empty keg.

Brew on

 

[user 204491]

I just put a ball lock post on my spiedel. Purge the keg once at 10 psi then transfer via pressure while the keg sits on a scale and I hold the prv open.
Go in the liquid dip tube so little movement is happening.
Then purge twice once full.

It worked great, only had to clean a keg and a hose, and never picked up more than 5g.
Was as much about being lazy as o2
Tasted good to me!

Can you elaborate on how you put a ball lock post on your Spiedel? Maybe add a photo? I would like to do pressure transfers from my Spiedels to my kegs as well.

 

[Rev2010]

Yeah, I forgot that you had previously mentioned the prefilling with liquid procedure. That method is more efficient of CO2 use than purging an empty keg.

After reading this I'm considering doing that method from now on as it does indeed seem to be a more efficient use of CO2 and also would sanitize the keg and line in one action rather than addressing them separately. The question I have though is what PSI is ideal to use? Like for example is 15psi fine and wouldn't 30psi use twice as much CO2 as pushing it out with 15psi and what extra benefit would using 30psi give over 15?

**EDIT - actually just been thinking more on this. What is the general sea level equilibrium pressure of CO2 in a keg? Meaning... let me explain here... if I were to push the sanitizer out at 30psi that would leave the keg pressurized right about 30psi (or fully at 30psi if I closed the faucet and allowed the gas to keep running until it levels to an exact pressure of 30psi). Well, then I shut off the gas and have to purge to allow the lid to open due to the pressure of course, so much of that gas is blown out -ie. wasted! So what would be a good psi to use to push out the sanitizer, leaving all CO2, but not waste too much CO2 when purging to open the keg to fill with beer?


Rev.

 

[day_trippr]

fwiw, I put the Star San filled keg on a work bench, hook up a drain line from the Out post back to my Star San reservoir bucket on the floor, then push with barely a couple of PSI and let the siphon effect do much of the work...

Cheers!

 

[doug293cz]

After reading this I'm considering doing that method from now on as it does indeed seem to be a more efficient use of CO2 and also would sanitize the keg and line in one action rather than addressing them separately. The question I have though is what PSI is ideal to use? Like for example is 15psi fine and wouldn't 30psi use twice as much CO2 as pushing it out with 15psi and what extra benefit would using 30psi give over 15?

**EDIT - actually just been thinking more on this. What is the general sea level equilibrium pressure of CO2 in a keg? Meaning... let me explain here... if I were to push the sanitizer out at 30psi that would leave the keg pressurized right about 30psi (or fully at 30psi if I closed the faucet and allowed the gas to keep running until it levels to an exact pressure of 30psi). Well, then I shut off the gas and have to purge to allow the lid to open due to the pressure of course, so much of that gas is blown out -ie. wasted! So what would be a good psi to use to push out the sanitizer, leaving all CO2, but not waste too much CO2 when purging to open the keg to fill with beer?


Rev.

For pushing liquid out of the keg, use the lowest pressure that gives you an acceptable flow rate. It the keg was completely full of liquid prior to purging, then the keg would be filled with 100% CO2 once the liquid was gone. If the keg was not completely full, then there would be a very small amount of residual air/O2, but the actual amount would depend on just how much headspace there was originally.

If you pushed at 30 psi, and then vented you would be dumping about 11.2 (30*5.5/14.7) gal of CO2, and leaving about 5.5 gal in the keg. If you pushed at 1 psi, and then vented, you would be dumping about 0.375 gal (1*5.5/14.7)

Brew on

 

[Jwin]

Can you elaborate on how you put a ball lock post on your Spiedel? Maybe add a photo? I would like to do pressure transfers from my Spiedels to my kegs as well.

I just grabbed an extra post and a washer and nut that that fit it at the hardware store.
installed it into the solid cap.
I'm sure there is a more professional way of going about it.
I'll try to add a photo later.
Once I acquire another solid cap I'm thinking of adding a 3 piece valve and barb. I just don't like the stock valve. It can squirt/leak out the vent hole if it gets slightly opened.

 

[IslandLizard]

@Rev2010
I've been using this liquid pre-purge method for about a year, 'cause sometimes I split a 6-7 gallon batch into two 3-3.5 gallon ones using different yeasts, finishing hops, adjuncts, etc.

Don't dump the Starsan, it will keep almost indefinitely in a large bucket for the next time, or just leave in a keg, and push it into another one when ready to use.

I did notice when not brewing or tinkering with beer for a few weeks (yes, it happens), the lid and the headspace sides in the Starsan bucket developing small black mold dots. Probably from condensation. I never see this problem when the bucket remains open, but then dust, fruit flies, and mosquitos get in. So either sponge them down every week, before they can develop, or rack to another bucket.

@doug293cz
Your observation that when racking without filling the headspace with CO2 is exposing the beer in the fermentor to air is one of my concerns too. Now since the exposure is brief, say 5-10 minutes, and the surface isn't turbulent, O2 absorption must be quite minimal.

When I used carboys, I pushed the beer out with a very low stream of CO2 using one of those rubber orange or auburn siphon caps. Buckets, although great in many regards, don't have that provision, although I've been thinking about drilling a second hole in the lids to flush with CO2 while racking and not even lift the lid until the racking (and even yeast harvesting) is done.

I drilled a 1" stopper hole in my 3.5 gallon bucket lids, which gives me utility access without unscrewing the lids, and I like that a lot.

 

[Jwin]

Can you elaborate on how you put a ball lock post on your Spiedel? Maybe add a photo? I would like to do pressure transfers from my Spiedels to my kegs as well.

Better late than never...

Obviously I need a ss washer, but since no liquid touches it and it is b only in n place for a few minutes, no biggy.
There is a rubber washer between the metal one and the cap. It squeezes around to post connection snug.
The nut is a compression fitting nut. The threads don't 100% match, but it's enough to grab it and apply pressure. I only put about 3psi on it.
I draw from the stock spigot using the hose/barb/qd you see attached to the autosiphon. It works with that as well. Just start the siphon and it goes down the dip tube, allowing me to keep the lid in place and the keg near closed.

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