Repitching onto yeast in Speidel

[JohnK93]

I've got my first batch, a bohemian pilsner with Wyeast Bohemian Lager, fermenting in my new 30L Speidel with the spigot on the lower port. Once this batch is done and into the keg, I'm planning on brewing a dunkel and tossing it onto the yeast cake.

I've never re-used yeast this way, I've always washed, so I have a couple questions. Do I leave all of the yeast in the fermenter, or will this result in over pitching? How do I know how much of the cake to leave/remove?

Second, if I drain from the spigot (no dip tube) into my keg, will this leave the yeast cake behind or does it drain pretty completely? Lastly, do I need to worry about contamination in the spigot? Should I remove and sanitize before my second batch?

Thanks,
John

 

[IslandLizard]

Yeast cell count typically multiplies 4-5 fold during a fermentation, so yeah pitching on a whole yeast cake will likely result in overpitching.
So you'd only use about 1/4 of the cake.
Use a yeast calculator such as HomebrewDad's to estimate the amount of yeast cells needed for a certain gravity batch.

Yeast washing is really not needed, you can save and store slurries with trub, and pitch those.
Read around this forum for different techniques and processes of harvesting and storing (used) yeast slurries.

If you don't tilt your 30 liter Speidel, about half a gallon (2 liters) of yeast/trub/beer will be left behind.

You should always clean and sanitize everything that comes in contact with your (chilled) wort and beer. So yes, clean that spigot and spray Starsan into it, until you're sure it's properly sanitized, before transferring your beer through it.

Beware of splashing beer when transferring, it will incorporate air (oxygen) and oxidize your beer. So either fill your keg through the lid opening with a racking hose from the spigot going all the way to the bottom of the keg. Or even better, read up on filling a 100% liquid pre-purged keg through the liquid out post, leaving the lid in place. That way no air will touch your beer. Extending that with some ingenuity, 100% closed transfers are possible. Very important for hoppy beers.

I would save/harvest the yeast slurry by pouring it into a large sanitized jar/jug/small bucket/etc. If you only want to save some yeast, stir the yeast cake up first, so you get a good representative mix of that colony, not just the top or bottom. Or scoop a cup or 2 out.
Then clean and sanitize the (Speidel) fermenter thoroughly, including the spigot assembly (remove and take apart), before putting a new batch into it. It's mostly the headspace krausen area I would be most concerned about as that has not been kept sanitized under beer. Also by emptying out the fermenter, air gets in. Air may contain contaminants, unless pre-filtered.