How do you know when keg is purged?

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BlackJaqueJanaviac

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How do you know when you've purged all the air out of a corny keg and there is only CO2 left?

The way my kegging setup is I have to chill and serve from 2 1/2 gallon kegs. I have 2 of these small kegs.

Right now I've got one empty 2 1/2 gallon keg, a full 5 gallon keg, and a near-empty 2 1/2 gallon keg on tap. I want to fill the empty keg from the 5 gallon corny today so that I can get it chilling before the other small corny goes completely empty. But that would leave the 5 gallon keg half empty for a few days while I'm waiting to empty the other small keg.

I learned from this forum how to properly jump from the big keg to the smaller ones. But so far the only way I've done it is to pressurize the empty keg to the same pressure as the full keg then let gravity siphon it down. I connect the two "in" posts and the air/CO2 go from the lower keg into the upper keg.

This works fine as long as I'm completely emptying the big keg. But I don't think it would be good to leave a half-full keg with a large headspace of air above it.
 

subliminalurge

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Why not let the co2 push the beer instead of gravity?

Connect the two liquid out posts with a jumper line, then connect the gas to the gas in post on the full keg. Set the pressure at just enough to move the beer and open the relief valve on the smaller keg. This way your 5 gallon keg isn't getting any air in it.

If you pressurize the small keg to even just a couple of psi before you start, by the time it's full of beer you should have nothing but co2 in the headspace of either keg.
 

944play

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BlackJaqueJanaviac said:
How do you know when you've purged all the air out of a corny keg and there is only CO2 left?
When the keg blows out the last of the StarSan (fill keg with no-rinse sanitizer and push it out with CO2).
 
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BlackJaqueJanaviac

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subliminalurge,

Thanks. Hmm. I may have to revisit this method. This is similar to what I originally tried but I would run into problems because the receiving keg would fill with foam.

Would it work to pressurize the receiving keg up to within 1psi of the full keg, then begin pushing the beer using the gas on the full keg and occasionally opening the relief valve on the receiving keg? Or would that result in too much foam?
 

944play

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Thanks. Do you recover the starsan and keep it for other use?
Usually, yes. I obviously have to have a clean vessel to put it in, and I don't always. I feel a lot better about reusing StarSan now that I prepare it with RO water and I can see that it's clear, not foggy.
 

subliminalurge

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subliminalurge,

Thanks. Hmm. I may have to revisit this method. This is similar to what I originally tried but I would run into problems because the receiving keg would fill with foam.

Would it work to pressurize the receiving keg up to within 1psi of the full keg, then begin pushing the beer using the gas on the full keg and occasionally opening the relief valve on the receiving keg? Or would that result in too much foam?
It sounds like you're transferring beer that's already carbed up. Why do that?

And how do you even know there's foam in the receiving keg? Don't you have the lid on?

In an earlier post you said you were pushing the beer into the "In" tube. That's the short tube that will have the beer falling from the top of the keg to the bottom. There's a foaming issue right there.

Use the "out" tube on the receiving keg. That tube goes all the way to the bottom so there will be less agitation of the beer.

Just pressurize the recieving keg to a few psi, connect the "out" posts of both kegs together, then gradually turn up the psi on your regulator just enough to get the beer to move. When it stops moving, vent a little from the receiving keg.

You really shouldn't be having foaming issues with this method if you're being gentle enough. Unless, of course, you're dealing with beer that's already carbed... In that case, then yes, leave the receiving keg pressurized and GENTLY AND SLOWLY vent gas just enough to let a little more beer move.
 

944play

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I would use the gravity transfer method under pressure:
Purge new keg as described. Pressurize with CO2.
Raise old keg.
Jumper both "out" ports together.
Vent new keg slightly until beer flows, then jumper "in" ports.
Allow to siphon, then remove jumpers once beer appears in gas jumper.

No foaming, no atmospheric contact, and most of the CO2 from purging the new keg gets recovered.
 
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BlackJaqueJanaviac

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944,

Yep. After I read your post that's what I envisioned. I just was wondering if I dump the 2 1/2 gallons of starsan or if it can be recovered and reused.
 
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