Purging keg with ferm CO2 anvil bucket

[rmr9]

Has anyone ever purged a keg using fermentation CO2 while using an anvil bucket fermenter?

I recently got a cold crash guardian from brewhardware and decided to run the long tube to a gas QD hooked up to a keg filled with starsan instead of to a jar of sanitizer for blowoff. My thinking was hey I can purge a keg and avoid oxygen in cold crash!

Well the bag on the cold crash guardian filled up like it should pretty quick so I closed it - good to go. Unfortunately no starsan was pushed from the keg.

I don’t think I have a leak - though it’s possible. Could it be because the anvil bucket isn’t rated for pressure? Did I hooked it all up about 36hrs into ferment did I wait too long?

 

[doogie]

I purge my kegs from my anvil bucket fermenter all the time, but I just have a hose from the anvil going into the beer port of the sanitized but empty keg and have an air lock attached to the gas port. If I'm going to cold crash, I add a bag to the air lock after a day or two of vigorous fermentation (so it's mostly if not all CO2) and let it suck that back into the keg. The anvil can only hold one or two psi, probably not enough to push out a full keg.

 

[rmr9]

Yeah, I was wondering about the one or two PSI not being able to effectively push a keg out. At this point I’m wondering if just dumping the starsan and trying to fill the keg carefully is the way to go. It’s an altbier so I’m not dealing with particularly delicate flavors.

Have you ever pushed starsan from a keg with bottled CO2? I’d like to limit the use of CO2 from my tank if I can but if its worthwhile I’d do it.

 

[Konadog]

I use a small C02 bottle to push StarSan out of my kegs all the time. I have SS BrewBuckets and have tried to use fermentation to push it out, but have the same issue. Sometimes it works to an extent, and other times it doesn't do anything. I'll stick with bottled C02 for now.

 

[doug293cz]

Your fermentation vessel needs to be able to hold about 2 psi to push out liquid (you're pushing against ~1 psi head with a full keg.) The good news is that you don't need to pre-fill the keg with liquid to get a good purge. Starting with an air filled keg, you can get down below 5 ppb (parts per billon) O2, by just routing all of the fermentation CO2 thru the keg (assuming your system is leak tight at about 0.5 psi, if it's leaky without pressure, all bets are off.) You can see the math here if interested.

Brew on

 

[rmr9]

Your fermentation vessel needs to be able to hold about 2 psi to push out liquid (you're pushing against ~1 psi head with a full keg.) The good news is that you don't need to pre-fill the keg with liquid to get a good purge. Starting with an air filled keg, you can get down below 5 ppb (parts per billon) O2, by just routing all of the fermentation CO2 thru the keg (assuming your system is leak tight at about 0.5 psi, if it's leaky without pressure, all bets are off.) You can see the math here if interested.

Brew on

Ah I saw that thread! I think in the future I’ll do the air purge method. If I used bottled CO2, would it burn through a tank fast?

 

[IslandLizard]

If I used bottled CO2, would it burn through a tank fast?

Depends on the size of the tank.

But yeah, pushing out 5.25 gallons of Starsan (or water) with your CO2 tank, leaving it at atmospheric pressure (same as the surrounding air), without any extra pressure left (0 psi on your regulator), takes 0.08 lbs (1.28 oz) of CO2.

Calcs:
1 lb of (liquid) CO2 = 8.74 cubic ft of gas at 14.7 psi (atmospheric pressure) ==> 1 cu.ft = 0.114 lb of CO2
1 keg is 5.25 gallon / 7.48 gallons/cu.ft. = 0.702 cu.ft.
0.702 * 0.114 = 0.08 lb (1.28 oz.) of CO2.

 

[rmr9]

Depends on the size of the tank.

But yeah, pushing out 5.25 gallons of Starsan (or water) with your CO2 tank, leaving it at atmospheric pressure (same as the surrounding air), without any extra pressure left (0 psi on your regulator), takes 0.08 lbs (1.28 oz) of CO2.

Calcs:
1 lb of (liquid) CO2 = 8.74 cubic ft of gas at 14.7 psi (atmospheric pressure) ==> 1 cu.ft = 0.114 lb of CO2
1 keg is 5.25 gallon / 7.48 gallons/cu.ft. = 0.702 cu.ft.
0.702 * 0.114 = 0.08 lb (1.28 oz.) of CO2.

So first and foremost thanks for the reply! I’ve never done this before so I apologize for the stupid question but…I would hook the CO2 tank up with the regular set at 0 and that would push the starsan out? While consuming only 0.08lbs of CO2?

Doesn’t sound like a big dent in a 5lb tank!

 

[IslandLizard]

I would hook the CO2 tank up with the regular set at 0 and that would push the starsan out?

No, at 0 psi you wouldn't be pushing anything out.
0 psi is the "theoretical" endpoint to use the minimum amount of CO2 needed to purge the keg.

In real life you'd push the Starsan out at 10-15 psi, and reduce the regulator pressure toward the very end so you would end up close to 0 psi (say at 2-5 psi) when you start blowing CO2 bubbles into the bucket or keg that receives the Starsan. Then pull the gas QD off the purged keg.
That way you'd waste the minimal amount of CO2.

 

[rmr9]

Well that was a “duh” moment right there! I think I’ll try the CO2 tank purge. I imagine it wouldn’t use THAT much CO2 to do, especially since I only brew 4-5 times a year.

 

[Spivey24]

I have a bunch of those anvil buckets. They are very iffy for holding any pressure. It depends how well the silicone ring is on and how tight your hooks are.

 

[rmr9]

I’ve had more and more trouble with that silicone ring as time has gone on. It’s a pain to get back in place once you remove for cleaning. That’s my only complaint about them.

 

[scrap iron]

I am purging a pre sanitized empty keg with fermentation co2 at this moment. I am using a 7.5 gal Anvil SS bucket with a co2 harvester hooked up to the outflow of fermenter. On the out side of the harvester I have a 3-piece air lock without the little cup and lid. A Evabarrier 4mm hose fits inside the air lock tube piece to keg out post and Evabarrier line from gas post to a jug with water for an end airlock. When fermenting is complete, I disconnect the lines to the keg and use the harvester to cold crash.
This is only the second time I've done this, the first keg I did it with is still carbonating so I'll see soon how it went. I add the corn sugar in the fermenter before closed transfer.
I hear you on the gasket, I had trouble too. I ordered a new set of gaskets and it took forever to get them. When I did get them I've started to use small pieces of siphon hose under the clamps to tighten the lid seal. It's been sealing pretty good now.

 

[Spivey24]

I’ve had more and more trouble with that silicone ring as time has gone on. It’s a pain to get back in place once you remove for cleaning. That’s my only complaint about them.

I have found it is much easier to replace that silicone gasket when wet. So now I starsan the lid and gasket and then put it back on right before use.

 

[rmr9]

It seems harder when the gasket is wet for me! I’ve read somewhere that apparently flipping the gasket the other way around helps if it’s not going in helps but I honestly haven’t tried yet. Not sure how that would change anything but hey if it works…