Hey everyone! This is my first post. I decided to join as i have been reading this forum for a while. I hope to turn this post into an all-revealing article on keg fermenting.
I recently obtained three free corny kegs from the brewer at my work. With a little maintenance and a new lid or two, these kegs ended up really improving my setup. Two of them are taller and thinner than the rest so they will not fit in my mini-fridge keggerator. They both still say 5 gal on the side. I think they are spartan style. This height makes them of less use for traditional kegging duties so I thought their only use to be for storing grains and/or hops sans oxygen.
Then I was looking at SS conical fermenters and also at their large prices. Somewhere I got the idea to look at using kegs for fermenters online. I thought it was brilliant. These kegs have a roughly conical shape at the bottom, minimizing surface area of beer/cake exposure. They don't have a bottom valve, but they do have the next best thing, a beverage tube! One of mine in particular goes all the way to the bottom an is bent to fit into the round divot in the bottom. Perfect for using pressure to push as much of the yeast cake as possible out through a cobra tap or similar.
I have no desire to ferment under pressure and also I have never used the tube/bucket method for air locks. My first batch in a keg was a secondary ferment. At first I tried just using an S airlock and a stopper with a hole on the gas in connector (threaded quick disconnect kind). It didn't work very well for two reasons, over time the angle of the airlock would sag threatening to fall off the connector. Also I thought I had a stuck ferment on my first primary batch using this method. It turned out that with all the poppets and springs and such somehow the co2 wasn't being allowed free passage. It was just building up in there.
So the next mod to the airlock setup was to block the metal tube connector off entirely and just shove a hole stopper into the top of the disconnect and shove the airlock into that. Of course the only way to make that work is to remove all the springs/poppets from under the post and also the disconnect so there's a straight shot from the tank to the airlock. Add a tubing clamp to the angled part and you have a great working airlock.
One of the main problems with keg fermenting is that if you are the kind that likes to throw the hydrometer in the batch it's more difficult to read. I recommend having a flashlight handy because it's dark in there. Also you have to feel around the top of the inside of the keg to make sure you get it clean.
Here's my method:
Rack from cooled pot into sanitized keg.
Top off with cool water.
Take a hydrometer reading.
Pitch yeast.
Attach airlock to poppetless post.
Primary ferment.
Being sure not to shake, attach co2 to re-poppeted gas post.
Attach cobra head with short amount of tubing to beverage post.
Remove yeast (NOTE: This does not remove all the yeast as he sides are not steep enough). extra : to remove more yeast give the keg a small shake after most of the yeast cake has been pushed out, then let sit for at least 20 mins and push more out.
Remove poppets, relieve pressure, and reattach airlock.
Continue to secondary ferment.
At this point I like to transfer into a shorter keg so that it'll fit into my fridge and also because I don't want the gunk on the sides of my serving keg (probably won't make a difference though, you could use the same keg). To do this you need two beverage connectors on the same tube. Connect the gas to the dirty fermenter keg (the full one), remove yeast once more and then connect the two beverage posts together. It's nice to have an unused gas post to pop on the receiving keg so you don't have to hold the pressure valve open. Also it's nice to purge the oxygen out of the receiving keg first. Turn on the gas and watch as the beer flows up one beverage tube and down another into an oxygen-less environment. When you hear sputtering you're done. Then cool, carbonate and serve, be sure to brag to friends about how this beer never touched oxygen after the pitch.
I've done a few batches this way, and so far I have never had a problem with head space. Then again I always use dry yeast that I sprinkle on top. Personally right now I don't know if I'll use carboys anymore unless there's some reason like I want to see what's going on or whatever. This system is a work in progress. One thing for those of you who use pure oxygen or even air to oxygenate your wort: in theory it should be really easy to connect oxygen to the bev/out port on your keg and just bubble through the liquid just like co2, then shake under pressure for added absorption. I welcome any comments, questions, suggestions, this forum has to offer. I hope that I have encouraged some of you thinking about using kegs as fermenters to give it a try. You can use a keg/lid that does not hold pressure at all. It just has to keep dust out. I think there are many advantages to doing things this way and perhaps with a little refinement and some group support this could be the standard for anyone with a keg setup.
For anyone who may be controlling temperature and want space measurements with my airlock installed, they are 27 1/2" tall and 9" diameter for the low profile kegs and 30" tall and 8 1/2" diameter for the firestone or spartan taller kegs.