German Brewing

As we all know, purging cornies can be tricky. Filling with Co2 and releasing the valve a few times doesn't eliminate oxygen; it simply dilutes it. A better method is to fill an empty corny completely with sanitiser and push it out using an inert gas. This is a good idea but won't work for me as I have cut all of my dip tubes short to allow me to ferment in cornies and also to leave behind settled material during transfers.

So, I have been playing around with some ideas and came up with the following technique. I don't own a DO meter so can't verify if it actually works. Any feedback from someone with a meter would be much appreciated.

Using the gas from fermentation to purge a corny
Once your beer shows signs of fermentation activity, sanitise a corny keg and use a jumper line to divert the gas from your fermentation vessel to the liquid out post on the corny. Attach a gas disconnect and blow off tube to the out post of the corny and submerge the end of the blow off tube in some sanitiser (or whatever).

This will force Co2 down through the dip tube of the corny and push the oxygen up and out through the gas out post. Over the course of a day or two I assume this would more or less completely purge the keg of oxygen (not just dilute the oxygen). In addition, the gas from fermentation is likely to contain sulphur, which will assist in scavaging oxygen once the beer is transferred to the corny for conditioning/lagering.

Here's a pic of one way to carry out the above procedure (I ferment in cornies but you could use just about any fermentation vessel as long as you can rig a jumper line between the fermentation vessel and corny and attach a blow off tube to the gas out post):

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Do you reckon this would work? I've tried it a few times and the beer seems to benefit but without evidence from a DO meter I can't be sure.

If you do this and then rack when there is enough gravity to carbonate your beer, I can't see any oxygen being an issue. Someone correct me if I'm wrong, of course

I've been using this technique for about two years (viewtopic.php?f=15&t=321). It doesn't purge all of the oxygen out of the keg, and I measured a pickup of about 0.3-0.4 mg/l when racking to a keg purged this way. I still do it, but I rack the beer with 1% remaining fermentable extract so that the yeast soak up that 0.3-0.4 mg/l while they finish fermenting and carbonating the beer.

Thanks for the replies. I'm racking the beer with a couple of gravity points to go too so it looks like I'm ok to continue with that technique.

I also have shortened my keg dip tubes however there is still a easy way to purge the kegs by displacing a fill of sanitizer solution. The trick is to also shorten the gas dip tube so that it does not extend into the keg. What you do is push out as much sanitizer as possible through your liquid post then disconnect that adapter and connect your CO2 tank to the gas post. Then pressurize the keg to ~50 lbs and invert the keg to where the gas post is at its lowest point and let your keg rest in this position for a little while to drain most of the liquid at this low point. Then using a spare gas post adapter, without a hose attached, connect it and the remaining solution in the keg will get blasted out. I do this outside and in small shots to get every last drop of sanitizer out. Remember to stop venting before the keg is completely empty of CO2 to keep a positive pressure for storage.

Normally I do this purge process with several kegs at a time by starting with approximately 7 gallons of hot starsan in one of my 8 gallon kettles with ball valve. I connect the kettle port via tubing to a liquid post connector, then via gravity fill the keg to overflowing from the gas port with the aforementioned gas post connector attached. When full of solution you tip the keg so the gas post is the highest point and verify complete fill by the absence of bubbles in the flow. Next step is to replace the spare gas post with your CO2 tank fill line and with a few pounds of positive pressure force the starsan solution back up into the kettle for reuse. The process is a bit messy because you lose a little solution with each keg overflow but that's the reason for starting with extra.

I usually do 4 to 6 kegs at a time this way to conserve sanitizer and leave the kegs in storage until I'm ready to fill.

That's clever. I'll definitely use that process on those occasions where I need a purged corny but I have nothing actively fermenting.

I do basically the same as Bilsch, but I use saniclean for its low foaming properties.


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Yea I guess I should think about trying saniclean instead so there would be less time waiting for the foam to collapse and drain from the kegs. On the other hand there isn't any shaking or turbulence when purging via gas pressure so I would assume there is little to no foaming going on in there.

I am using 20l kegs with A-Type spears.

When going into secondary it is not necessary to purge the vessel since the remaining fermentables and active yeast act as sufficient anti-oxidant.

Such precautions are only necessary Post-Filtration or when racking it off the yeast after conditioning.

My spears are not shortened btw. It's not necessary and makes it possible to 'dump' yeast by pushing it out through the spear.

Not having to deal with 7/16 fittings is bliss!

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How much space lies between the spear and the bottom of the keg? From what I remember the sanke's the brewery I worked at used had like 1/4 inch spacing, so if there was any sedimentation it would get trapped there and come off slowly through the serving of the keg.