Is anyone using fermentation CO2 to purge their kegs?

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J2W2

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Hi,

I've been trying to reduce my oxygen exposure over the past year or so. Stopped using a secondary, added a CO2 collector to pull CO2 back in during cold crash, went to a closed loop transfer, and purging my kegs by forcing liquid out with CO2 before filling the keg. I'm not sure how much CO2 a purge uses; I set my regulator just high enough to force the liquid out, but I'm still using CO2. I started wondering if there was another way to accomplish this, and I started thinking about using the CO2 lost during fermentation.

I just kegged my latest beer, so it will be another couple of months before my next brew, but I've been playing with the idea in my head. There are several issues I'd need to work out for my setup. I ferment in my old kegerator, which has four bolt holes in the top where the tap tower was mounted. I use one of them to feed the probe for my Inkbird controller. I'd probably try to use one of the holes to thread tubing from my fermenter's blow-off out of the kegerator. From there I think I'd need some kind of initial collector, in case of blow-off. I have a couple of one-gallon Big Mouth bubblers, so I was thinking one of those with son Star San in it. From there the tubing would run to a gas connector for my keg. One concern would be building it air tight, so that it generates enough pressure to purge the keg. I'd also have to let everything run for a while before I started purging the keg, to make sure the entire setup was full of CO2.

Is anyone doing this already? Any thoughts/pointers? Thanks for your help!
 

day_trippr

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Last year I started doing what I think is what you're thinking of doing. I outfitted two of my fermentation fridges with bulkheads to run fermentation gas out and over to where I could park two to four kegs for purging. And, concerned with potential blow-off issues, I ran 1/2" pvc tubing from the carboy caps into tight lidded 1/2 gallon size plastic jugs and ran 5mm ID EVABarrier tubing out of the jugs and through the bulkheads to the kegs....

1643407918400.jpeg



Ferm-gas lines are labeled for the respective fridges...

1643408094083.jpeg



Cheers!
 
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J2W2

J2W2

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Last year I started doing what I think is what you're thinking of doing. I outfitted two of my fermentation fridges with bulkheads to run fermentation gas out and over to where I could park two to four kegs for purging. And, concerned with potential blow-off issues, I ran 1/2" pvc tubing from the carboy caps into tight lidded 1/2 gallon size plastic jugs and ran 5mm ID EVABarrier tubing out of the jugs and through the bulkheads to the kegs....

This is pretty much exactly what I was thinking. One issue with my plan would be tubing size. I believe the bolt holes in my kegerator are 1/4", which would only allow very small tubing to pass through. I think that may cause issues during very active fermentation (getting a lot of CO2 through a tube that small) and possibly not generating enough pressure to purge a keg. I don't want to mess up the bolt holes by drilling one out, as I do repurpose the kegerator back to a kegerator on rare occasions. My other, and probably better option, would be to bring a larger tube through the plastic cap that plugs the top of the kegerator where the beer lines enter the tower. I think I could install a bulkhead in that, which would allow for larger tubing throughout.

Another thought I had, that isn't really practical for the way I cycle kegs, would be to use the keg that just ran out to purge the new keg. I'm guessing there's enough CO2 in one fully pressurized empty to purge a number of kegs. I'm thinking just a gas-to-gas connection between the kegs.
 

day_trippr

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Pretty sure it takes a dozen or more "flush cycles" to actually bring the residual oxygen density down where we'd like it to be, so I'm not very confident one keg pressurized to say 12 psi contains enough CO2 to do the job. It'd be a start, for sure, and I've often considered using kicked kegs for that purpose. But then I remember a fermentation produces prodigious amounts of CO2 in excess of that needed, so I don't bother :)

Cheers!
 
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J2W2

J2W2

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Pretty sure it takes a dozen or more "flush cycles" to actually bring the residual oxygen density down where we'd like it to be, so I'm not very confident one keg pressurized to say 12 psi contains enough CO2 to do the job. It'd be a start, for sure, and I've often considered using kicked kegs for that purpose. But then I remember a fermentation produces prodigious amounts of CO2 in excess of that needed, so I don't bother :)
I was talking about kicked kegs (just didn't word it quite right). They should be pure CO2 at serving psi, or close to. But as I said, that process wouldn't really work for me. I cycle six kegs for my five keg keezer, and by the time I pull a kicked keg, I've already got the replacement filled and on CO2 for a couple of days.

I think I'll definitely try the fermentation CO2 purge next time. Thanks for the info on your setup!
 

Knightshade

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Last year I started doing what I think is what you're thinking of doing. I outfitted two of my fermentation fridges with bulkheads to run fermentation gas out and over to where I could park two to four kegs for purging. And, concerned with potential blow-off issues, I ran 1/2" pvc tubing from the carboy caps into tight lidded 1/2 gallon size plastic jugs and ran 5mm ID EVABarrier tubing out of the jugs and through the bulkheads to the kegs....

View attachment 757262


Ferm-gas lines are labeled for the respective fridges...

View attachment 757263


Cheers!

This seems like something that should have been completely obvious to me, but seeing it in practice has been the 'light bulb...' thing that I needed.

I manage to squeeze my 6G torpedo fermenter, 1 5G corny filled with Star San, its receiving empty counterpart also a 5G corny, which is then connected to a small mason jar of Star San as final blow off. I've definitely had some muck get into the tubing and possibly (most likely) into the 1st Star San filled keg from the Torpedo as a result of high krausen.

Using an intermediary container (that looks like a peanut jar w/nylon barb fittings in the lid, and a duo tight bulkhead one?) seems like it would totally take care of that issue. My wife is about to finish off a container of Costco mixed nuts that kind of looks like that container you're using..
 

Dland

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I know some people use fermentation gas to displace starsan, I use it to displace the air in previously sanitized kegs, is easier and just as effective.

Below is an earlier thread on topic:

 

day_trippr

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The containers were bought empty from Amazon, and indeed have nylon 1/2" barbs screwed into pvc 1/2" half-couplers (an actual 1/2" coupler I sawed in half) , and with JohnGuest 1/2" mpt to 5/16" OD bulkheads. A wrap of electrical tape is sealing insurance in case the lid insert isn't evenly engaged by the container rim...

Cheers!
 
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J2W2

J2W2

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day_trippr, do you purge your 1/2 gallon blow-off jugs somehow before you start the process? Or maybe let the very first fermentation CO2 purge it before connecting it to your kegs? Seems like there would be some O2 getting in if you didn't; unless the continuous CO2 from fermentation eventually purges it as well.
 

Brooothru

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Pretty sure it takes a dozen or more "flush cycles" to actually bring the residual oxygen density down where we'd like it to be, so I'm not very confident one keg pressurized to say 12 psi contains enough CO2 to do the job. It'd be a start, for sure, and I've often considered using kicked kegs for that purpose. But then I remember a fermentation produces prodigious amounts of CO2 in excess of that needed, so I don't bother :)

Cheers!
I clean my kegs, then soak them filled to the brim with Star San. After soaking, I dump the Star San, add ¼ tsp NaMeta to the keg and fill with warm water (to make sure the Meta dissolves). Then I hook up the blow out line of my fermenter to a Gas In quick disconnect and hook that up to the gas in post on the keg. I have a discharge line on the Beer Out post that forces the NaMeta solution into a discharge bucket.

After a hour or so, the CO2 discharge from the fermenter blow off line has pretty much displaced all the NaMeta solution from the cleaned and sanitized keg, leaving it fully cleaned and purged of oxygen. There's always a little NaMeta solution left in the keg which didn't get pushed out by the CO2. For that problem, I shortened my Gas In dip tubes on my kegs so that they are essentially flush with the inside port of the keg post. I shoot a few PSI of bottled CO2 into the keg, turn it upside down in a laundry sink, and then depress the poppet to eliminate any residual liquid.

Now I have a cleaned, sanitized, sealed, CO2 purged keg, ready for a closed transfer of finished beer from a fermenter. But I usually add one final step. It's said that bottled CO2 isn't totally free of gaseous oxygen. Probably true, but to what extent it affects home brew in a keg is open for debate. So I figure as long as I've got an active fermentation going on, pumping out an estimated 25 volumes of "pure" CO2, why not just hook the fermenter back up to the Gas In port on the keg and attach a spunding valve with a black QD set at ~2 psi to the Beer Out post and do another keg purge with "pure" CO2.

Two birds, one stone. If early in the fermentation and the beer is a lager or some other low ester brew, having 2 psi can help suppress undesired flavors. If late in the fermentation when the process has slowed, I dial up the spund to around 15 psi to naturally carbonate the beer and also prevent suck back when I cold crash. At the same time it provides some initial head pressure when I start the closed transfer to a previously purged keg. I started doing this process nearly three years ago when I upgraded my SS conical to a unitank. It's simple, easy and effective. I can also daisy-chain multiple kegs to sanitize and purge with a single batch of Star San and NaMeta, though sometimes it's hard to keep an even flow of liquid moving without elevating one or more vessels for a gravity assist. For gas purging of empty kegs, however, it's a no brainer.
 

marc1

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I ferment in a Kegmenter. I jumper that to my 2 serving kegs for the batch in series, and put a spunding valve on the gas connect of the second one, set to a low PSI to ensure the lids stay seated.
 

day_trippr

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day_trippr, do you purge your 1/2 gallon blow-off jugs somehow before you start the process? Or maybe let the very first fermentation CO2 purge it before connecting it to your kegs? Seems like there would be some O2 getting in if you didn't; unless the continuous CO2 from fermentation eventually purges it as well.

I hook everything up as soon as I've pitched and oxygenated the wort. And I have it on good authority that fermenting 10 gallons of beer produces more than enough CO2 to fully purge a pair of kegs plus those two half gallon vessels. No need to pre-purge or partially purge anything...

Cheers!
 

_BullDog_

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I keep 1 keg with starsan and then when I need a purged keg i just hook the gas line to the in post and run the out to the clean empty keg.

this leaves me with a clean sanitized and purged keg.

move gotten a couple kegs purged per fermentation when I stay on top of swapping them out.
 

jerrylotto

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I have a gas post on the top of my conical fermentation setup. I clean my keg and then fill it with about a 1/2 gal of sanitizer solution, connect the liquid out post on the keg to the gas out on the fermenter. When i start out, the gas in on the keg has a bubbler attached. When things slow down, I switch to a spunding valve set to about 5 psi.. Never tried to daisy chain multiple kegs but now I plan to try it.

PS - the idea of daisy chaining kegs appealed to me enough that I added a few inline to my current lager fermentation which is just started.
 
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I am trying this for the first time right now, but I set up a Blow-tie spunding valve on the purging keg (it was emptied of StarSan dregs by holding upside down and opening the PRV). I expected some level of pressure to build up which I would then adjust, but so far it's as if the Blow-tie isn't holding any pressure. It is probably pilot error, as I have never used one before, but I will check it again later today and see if there is any change. I figure I should also be getting aromatics from the primary ferment through the keg and out the Blow-tie, but so far nothing. I may need to check the parts drawer and see if I can put together a daisy chain between all cleaned and empty kegs, too.
 

marc1

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I am trying this for the first time right now, but I set up a Blow-tie spunding valve on the purging keg (it was emptied of StarSan dregs by holding upside down and opening the PRV). I expected some level of pressure to build up which I would then adjust, but so far it's as if the Blow-tie isn't holding any pressure. It is probably pilot error, as I have never used one before, but I will check it again later today and see if there is any change. I figure I should also be getting aromatics from the primary ferment through the keg and out the Blow-tie, but so far nothing. I may need to check the parts drawer and see if I can put together a daisy chain between all cleaned and empty kegs, too.

I hit the kegs to ~5PSI or so with my CO2 tank, so there's a little pressure in there to begin with. I start the valve screwed all the way in and then loosen it until I can just start to hear the gas escape.
 

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I hook everything up as soon as I've pitched and oxygenated the wort. And I have it on good authority that fermenting 10 gallons of beer produces more than enough CO2 to fully purge a pair of kegs plus those two half gallon vessels. No need to pre-purge or partially purge anything...

Cheers!
This is correct. The analysis I did assumed that the keg and fermenter headspace started with air (i.e. no pre-purge or liquid fill.) The result was that a mid OG beer could reduce the residual O2 in the purged keg to ~5 ppb (parts per Billion). The analysis itself was done for worst case air and CO2 mixing, and ignored the effect of the CO2 flow sweeping out some of the O2. Thus the actual results are even better than the analysis predicts, and this has been confirmed by people with the required instrumentation, but the data is behind a paywall, and I don't have a link.

So, there is no need to over complicate things. Just hook up a sanitized keg (beer post) to the blow-off of the fermenter, and add an airlock or spunding valve to the gas post of the keg. For best results, you should use O2 permeation resistant tubing (EVA Barrier). Silicone tubing is the worst choice for O2 permeation. If you are worried about krausen blow-over, put a "slobber box" between the fermenter and keg, and put a little water with Fermcap in the bottom of the slobber box.

Finally, I never understood the desire to daisy chain multiple kegs (more than needed for the batch being fermented) for purging. Before you can fill a keg, you have to ferment something to put in it. Why not just purge when you ferment the future contents of the keg?

Brew on :mug:
 
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DuncB

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@doug293cz
I'd say the only reason to purge and pressurise multiple kegs with CO2 from ferment is to use the harvested and pressured CO2 to drive your transfer if you can't get a decent height to run the closed transfer loop in a timely fashion. Or for serving beer if you can't get a CO2 cylinder or want to be a bit more eco.
 

doug293cz

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@doug293cz
I'd say the only reason to purge and pressurise multiple kegs with CO2 from ferment is to use the harvested and pressured CO2 to drive your transfer if you can't get a decent height to run the closed transfer loop in a timely fashion. Or for serving beer if you can't get a CO2 cylinder or want to be a bit more eco.
The residual O2 analysis is only valid for the first keg in the chain, and assumes atmospheric pressure. If you collect at significant pressure, you get fewer gas "turn-overs", so the residual O2 will be higher. If purging daisy chained kegs, the residual O2 will be higher in each successive keg. Purging multiple kegs with larger batches (2 for 10 gal batch, 3 for 15 gal, etc.) should not create any issues. Results for any specific system may be good enough, but you should do your own analysis or testing to be confident.

Brew on :mug:
 

Brooothru

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Finally, I never understood the desire to daisy chain multiple kegs (more than needed for the batch being fermented) for purging. Before you can fill a keg, you have to ferment something to put in it. Why not just purge when you ferment the future contents of the keg?

Brew on :mug:

This does present a few complications and complexities, but if you have multiple kegs that have been cleaned, sanitized and sealed, it's a good way to at least accomplish a CO2 purge of the daisy-chained kegs. I've got an assortment of 12 kegs and occasionally find myself emptying more than one between brew sessions. At any given time I might have many as 6 kegs in rotation: two in the kegerator on tap and four in the beer fridge lagering or conditioning. If I kick a keg or two between brew sessions, like right now for instance (I haven't brewed since October) the number of empty cleaned kegs in need of purging mounts up.

Since I likely won't be brewing before mid-March, I'd have to do quite a few batches in quick succession to purge 6 or more kegs @ one keg per fermentation, so daisy chaining gives me multiple purged kegs on hand for closed transfers when needed. I also have a large kegmenter that I use for conditioning and spunding that I store cleaned and purged with ~5 psi head pressure like my kegs, and like to store my empty conical and unitank cleaned and purged as well. Sure saves on CO2 tank refills.
 

doug293cz

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This does present a few complications and complexities, but if you have multiple kegs that have been cleaned, sanitized and sealed, it's a good way to at least accomplish a CO2 purge of the daisy-chained kegs. I've got an assortment of 12 kegs and occasionally find myself emptying more than one between brew sessions. At any given time I might have many as 6 kegs in rotation: two in the kegerator on tap and four in the beer fridge lagering or conditioning. If I kick a keg or two between brew sessions, like right now for instance (I haven't brewed since October) the number of empty cleaned kegs in need of purging mounts up.

Since I likely won't be brewing before mid-March, I'd have to do quite a few batches in quick succession to purge 6 or more kegs @ one keg per fermentation, so daisy chaining gives me multiple purged kegs on hand for closed transfers when needed. I also have a large kegmenter that I use for conditioning and spunding that I store cleaned and purged with ~5 psi head pressure like my kegs, and like to store my empty conical and unitank cleaned and purged as well. Sure saves on CO2 tank refills.
Why do they need to be purged soon after they are emptied? I can see the benefit of cleaning quickly, but that's about it.

Brew on :mug:
 

DuncB

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The residual O2 analysis is only valid for the first keg in the chain, and assumes atmospheric pressure. If you collect at significant pressure, you get fewer gas "turn-overs", so the residual O2 will be higher. If purging daisy chained kegs, the residual O2 will be higher in each successive keg. Purging multiple kegs with larger batches (2 for 10 gal batch, 3 for 15 gal, etc.) should not create any issues. Results for any specific system may be good enough, but you should do your own analysis or testing to be confident.

Brew on :mug:
If I remember your comprehensive analysis it applied to " air " filled kegs. In my case each keg is filled with starsan and purged with ferment CO2, this can be done as a daisy chain process. You did acknowledge that this would reduce the O2 level further. The oxygen that is inevitably dissolved in the starsan might have less effect with this technique. I agree a DO meter to check this out would be ideal.
Everyone wants a CO2 meter at the moment to check airflow in rooms is high enough to reduce covid transmission.
 

doug293cz

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If I remember your comprehensive analysis it applied to " air " filled kegs. In my case each keg is filled with starsan and purged with ferment CO2, this can be done as a daisy chain process. You did acknowledge that this would reduce the O2 level further. The oxygen that is inevitably dissolved in the starsan might have less effect with this technique. I agree a DO meter to check this out would be ideal.
Everyone wants a CO2 meter at the moment to check airflow in rooms is high enough to reduce covid transmission.
O2 meters that are accurate in the ppb range are extremely expensive. If a meter can't measure ppb levels, it's pretty much useless for DO testing. If you stick to the simple process, you don't need one.

If you are going to purge liquid filled kegs with fermentation gas, you should let the fermentation proceed a bit to clear the air out of the fermenter headspace. Otherwise, it will just get pushed into the kegs, defeating the purpose of the liquid fill. Figuring out when to connect the fermenter to the liquid filled kegs is left as an exercise for the reader.

Brew on :mug:
 

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I do wait until fermentation is well under way before starting " the purge ".
As we know the beer is cheap, just supporting the hobby is the expensive part.
 

Brooothru

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Why do they need to be purged soon after they are emptied? I can see the benefit of cleaning quickly, but that's about it.

Brew on :mug:
What I do is clean, sanitize with Star San, dump the Star San, then treat with NaMeta and hot water, then displace with CO2, either bottled or preferably with fermentation gas. If I've got a fermentation going, I'll use that to purge the keg while displacing the Meta and end up with a cleaned, sanitized 'pure' CO2 purged keg. If I don't have an active batch fermenting, I'll clean and sanitize the kicked keg(s) and leave them empty but sealed. Then when I have a fermentation going, I'll hit the keg with NaMeta and hot water and use discharged CO2 for the displacement purge.

If I have multiple empty (but cleaned and sanitized) kegs, I'll fill one with NaMeta solution and then displace it into a daisy-chained keg (or kegs). Because of the difficulty maintaining a consistent rate of flow from one to the next keg, I seldom daisy chain more than two kegs together at any one time. It's a pain to keep the flow going with three, and an exponentially frustrating chore to keep four kegs purging simultaneously. I've only done four a couple of times, and the experience convinced me to plan better between purging and brew sessions.
 
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My first keg purge from fermentation is under way. Discovered why there was no pressure in the Blow-Tie spunding attachment-it was leaking out of the duo-tight parts. I keep seeing people extolling their virtues, but every time I got one to seal another opened up, and by the time I got through the last, the first was leaking again. Makes me nervous about hooking up a CO2 or liquid system. I opted to just attach a hose in a bucket of Starsan to the keg post and put the spunding valve on the shelf for now. It's bubbling away, so that's positive.
 

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I do wait until fermentation is well under way before starting " the purge ".
As we know the beer is cheap, just supporting the hobby is the expensive part.
If you are purging air (or gas) filled kegs, hook up at the start of fermentation. If you are purging liquid filled kegs, see here.

Brew on :mug:
 

doug293cz

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My first keg purge from fermentation is under way. Discovered why there was no pressure in the Blow-Tie spunding attachment-it was leaking out of the duo-tight parts. I keep seeing people extolling their virtues, but every time I got one to seal another opened up, and by the time I got through the last, the first was leaking again. Makes me nervous about hooking up a CO2 or liquid system. I opted to just attach a hose in a bucket of Starsan to the keg post and put the spunding valve on the shelf for now. It's bubbling away, so that's positive.
Did you make sure to seat the tubing all the way to the stop in the fittings? Leaks are common in those types of fittings if the tubing is not inserted far enough.

Brew on :mug:
 

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I’ve been doing this with great success for over a year because of the analysis shared. If I do any
Sounding it is on the fermenter as there
Is less chance for leaks that way. I have had hoppy beers in kegs for a couple months that still tasted great. I also close
Transfer and use ascorbic in mash for combatting O2.
 

marc1

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I’ve been doing this with great success for over a year because of the analysis shared. If I do any
Sounding it is on the fermenter as there
Is less chance for leaks that way. I have had hoppy beers in kegs for a couple months that still tasted great. I also close
Transfer and use ascorbic in mash for combatting O2.

How are you purging the kegs if you have the spunding valve on the fermenter?
 

Smudgey

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How are you purging the kegs if you have the spunding valve on the fermenter?
I put a T-join in before the spunding valve and a couple of duofit 1/0 valves, but you could as easily use the CO2 on exit from the valve.

I hate wasting anything and watching 25 volumes of free CO2 bubbling away peeved my scottish ancestors everytime I go to the garage for a sample. Which is admittedly quite often because of said ancestors. So I bought a few small items and now use the fermenter for purging kegs and lines, conditioning a brew in the kegerator and serving as well. It's an easy change if you already pressure ferment and have a spare keg. It's a tiny fraction of a saving - but its satisfying and filling a bottle is a 3 hour round trip for me.

After pitching I let it blowoff for a day or until its fermenting happily, then I use the T-join line from the fermenter (with the spunding valve closed/ set high) to starsan-purge a keg, then add another in series to purge that over a day or 2 as well. This all runs into a third corny and bubbles through that. Maybe the slight back-pressure keeps the krausen down, - I've never had krousen trouble anyway.

When the yeast's had a good start and the kegs are purged I attach a cheap inline regulator set at 12psi to the last keg in series. This will go to the kegerator. The inline regulator keeps the pressure backwards in the system set by the spunding valve ( now 15psi) and sets the serving pressure (12psi) forwards from there to the kegerator. When it all gets to pressure I plug it into the kegerator and leave it for most of the fermentation. This finishes conditioning a new beer/ keeps a keg at serving pressure in the kegerator for the ferment time.

At least a few volumes from the end of fermentation I remove one of the kegs sitting at 15psi to close transfer to later and up the blowtie to 30psi (bluetooth hydrometre helps to guess when). This carbonates the beer at ~18° in the fermenter to 2.5 volumes and also charges the remaining purged keg to 30psi. I find that's enough CO2 stored to keep a keg [email protected] 12psi until it kicks (P1xV1=P2xV2 30psi x 20L = 12psi x 40L + 20% extra), with the bit extra for thermal contraction and for some hissing moments. Its not an exact science for me but seems to work. I plan to get an old 50L keg as a dedicated CO2 tank - it would give more flexibility around brewing times and serving multiple kegs.
 

Bassman2003

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I clean my kegs, then soak them filled to the brim with Star San. After soaking, I dump the Star San, add ¼ tsp NaMeta to the keg and fill with warm water (to make sure the Meta dissolves).
Thanks to everybody for sharing their process. Broo, just wondering - why the sulfite addition when you just blow it out? Isn't there a risk of flavor impact if some is left behind? Also, if nothing is in the keg, what is the meta scavenging? Maybe the small amount of liquid that stays in the keg?
 

ba-brewer

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Brooothru

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Thanks to everybody for sharing their process. Broo, just wondering - why the sulfite addition when you just blow it out? Isn't there a risk of flavor impact if some is left behind? Also, if nothing is in the keg, what is the meta scavenging? Maybe the small amount of liquid that stays in the keg?
It's a three step process. First, clean. Second, sanitize with StarSan. Third, scavenge O2 with Meta. The keg remains sealed after adding the Meta. What little O2 that's in the keg gets bound with sulphur and discharged with the sodium when CO2 from the fermenter displaces the liquid and gases in the keg (at least that's how I understand the chemistry operates; caveat: it's been more than 50 years since I struggled through Freshman Chem 101).

There always seems to be some liquid left in the keg after the bulk of the NaMeta solution is displaced by the discharge CO2, so the keg ends up basically filled with "pure" CO2 and an ounce or two of NaMeta solution. I've shortened all my Gas-In dip tubes so that they're essentially flush with the inside of the keg. I shoot a couple psi of bottled CO2 into the keg, hold the keg upside down in a laundry sink, and then depress the keg post poppet just long enough to flush the last of the Meta solution. Ideally, the keg is now sealed from outside sources, cleaned and sanitized, and purged of oxygen displaced by CO2, ready for storage. Any residual O2 from the bottled CO2 should chemically react with any residual Meta in the keg (forming SO2?) and be vented out when the keg eventually gets filled.

In theory this should be similar to wine production where sulfites are added to the wine just before bottling. The sulfites bind with any oxygen in the wine or in the ulege (headspace between the cork and the wine). When the wine is uncorked you often get a small whiff of sulfur. The process of decanting and swirling a freshly poured glass is to let it "breathe" to dissipate that faint sulfurous smell. I'm fairly sensitive to the smell of sulphur compounds, but I can't say that I've ever noticed it in any of my beers handled this way. It could be that any sulphur gets vented out of the keg when it first gets tapped, however it's not noticeable in the glass.
 

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