Conical fermenter

brewfun said:

JohnB said:

by opening the valve and lowering the volume of the liquid (without the above mentioned airlock) don't you also allow oxygen to enter the fermenter?

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In a very general way, yes. But that is far from the whole story. If you feel the need to stop the possibility, you can just run some low pressure CO2 through the same opening to maintain positive pressure.

When you're removing yeast from a conical, you're only concerned with the spent yeast. This is the thickest portion of the the yeast cake, which is the very bottom of the cone. You'll stop when you see a slight color change to creamy, fresh looking yeast. You don't just open the valve and let it just flow, you try to maintain a slow flow to prevent making a hole in the yeast cake. The center of the yeast cake will fall faster than the sides, in the same way that you see when milling grain.

So, the amount of yeast that's dropped will be pretty small compared to the whole. You do this a little at a time over 4 or 5 days and you'll start to see very thin runnings, which means most of the yeast is gone.

I like the setups where a piece of 1.5" stainless pipe is attached to the come valve and allows the yeast to settle into it. A couple of days past primary, just close up the valve, remove the piping and a large portion of the yeast is removed. Repeat and you have both a clear beer and a nearly aseptic method for repitching. [Pro Tip: one foot of 1.5" holds almost 12 ounces]

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