Ever flush your kegs with CO2 from primary?

[Ike]

Something tells me I'm WAY overthinking this, and a search didn't turn anything up, but...

The local gas distributor is pretty proud of their CO2 fills, with a recent price increase "because the gubmint made us put 'beverage grade' all over everything." Here I am, listening to the "blub blub blub" of a ginger beer batch fermenting away in all its glory, and I got to thinking...

Can I take my kegs, clean/sanitize all the interior workings, leaving maybe a couple cups of starsan in each one. Then, hook the blowoff tube from a primary fermentation to a beer-out ball lock, connect it to the keg, and remove the pressure release valve on the keg? I figure I'd give it an hour or so, come back, disconnect the line and replace the PRV. Pressure would never get over ambient, but given enough time the O2 should be pretty much gone, especially if I'm giving it a push by filling from the bottom.

This SHOULD yield me a keg that's (reasonably) flushed with CO2, with a small amount of starsan in it. Before use, give it a really good shaking to redistribute the star san and re-sanitize the interior, pump out the star san with pressure and fill from primary by any of the "no oxygen exposure" methods you all suggest here.

Anybody else do this?

OR

Anybody else pre-sanitize and pre-flush their kegs by any other means?

OR

Am I COMPLETELY over-complicating things, and I should just forget about the small savings in CO2 fill costs?

 

[Bensiff]

Seems like way too much work for me for way too little gain. If I'm that concerned about the cost of brewing that I'm trying to save a few cents on CO2 I will find other ways to reduce my costs and keep hooking up my CO2 tank to purge my kegs and leave capturing CO2 from the ferments to the Germans.

Real deal about the government getting its nose into the gas industry according to a friend who is a manager at a welding/gas supply chain. He said it has to do with concerns of terrorists getting into the food supply chain. So, while discussing the validity of that is better suited for the debate forum, it remains that increased regulation is increasing our CO2 costs.

 

[IslandLizard]

Aside from the amount of work, any bugs could flow in with the reclaimed CO2. The recovery keg may still contain a significant amount of air (and O2). Hard to measure.

If you fill a keg with Starsan, all the way to the top, liquid flush with the rim of the lid opening, then place the lid and push out all the Starsan with CO2, you will have used around 5.5-6 gallons of CO2 gas. That is the most economical way for your keg to be (nearly) 100% filled with CO2. That's not a huge expense for filling a keg with beer, even if you only fill it half or 3/4 way. It shouldn't even require purging, but if you do, it's only a small amount for the extra security. You could use priming sugar to naturally carbonate to save some gas, but again, sugar is not free either, and it takes additional time.

How large is your CO2 tank? 20# is a very economical size. I can get it filled for $24, but I paid around $28 for a swap last time, which provided me with a tank that's in-date again. Yes, there's a sticker on it that claims it to be beverage grade CO2. Never seen that before.

Smaller sized tanks tend to run more $ per pound.

 

[Ike]

How large is your CO2 tank? 20# is a very economical size. I can get it filled for $24, but I paid around $28 for a swap last time, which provided me with a tank that's in-date again. Yes, there's a sticker on it that claims it to be beverage grade CO2. Never seen that before.

Smaller sized tanks tend to run more $ per pound.

This is my real pain: the nearest fill station (a Norco) charged me $23 to fill a FIVE pound cylinder. They tried to talk up the cost effectiveness of a 20# cylinder, but IIRC the price for that was something like $80. That's just for an exchange, not a whole new cylinder.

There's another place to fill that's about a 20 minute drive. I'm going to call 'em up in the morning to see what they're charging. Around here, 20 minutes is a bit of a hike, but if it saves me much green it will be more than worth it.

Ike

 

[IslandLizard]

This is my real pain: the nearest fill station (a Norco) charged me $23 to fill a FIVE pound cylinder. They tried to talk up the cost effectiveness of a 20# cylinder, but IIRC the price for that was something like $80. That's just for an exchange, not a whole new cylinder.

There's another place to fill that's about a 20 minute drive. I'm going to call 'em up in the morning to see what they're charging. Around here, 20 minutes is a bit of a hike, but if it saves me much green it will be more than worth it.

Ike

I'd call around and find a more reasonable supplier, and probably invest in a larger tank. They make 50# ones. Just don't have a leaky keg in the keezer.

Have you tried a beverage supplier? Maybe a brewery?

A couple months ago I started calling around to get my then (barely) out of date, 20# aluminum tank exchanged rather than getting it hydrotested myself. The prices for fills and exchanges were all over the map, and it looked I had to pick up the cost for the hydrotest anyway, around $15-25, even on an exchange. The prices I mentioned in my previous post were among the most reasonable, but I got quotes as high as $40-$50 for a refill, with my LHBS taking the crown with $3.40 a pound, regardless of fill volume! Some were claiming I needed "medical" grade. Yeah right!

So when I went to the most promising outfit for the exchange, he looked at my tank and said, "Oh we'll take that, no cost to you for the hydrotest. You know, sometimes people bring tanks from the last century..." and handed me one of their full, shiny tanks in return. He's getting my business.

 

[DaWhip]

I just set this contraption up to allow me to do a pressure fermentation of full 5 gallons in a 5 gallon corny. Far right QD goes on the fermenter. A second keg will be connected to catch krausen with the two "down" lines. Once fermentation settles down a little, I should be able to purge a keg with it. All of this is theory at this point as I have not brewed with it yet. It will have it's first go this weekend if UPS ever shows up with my hops.