When pitching on a yeast cake is it necessary to clean the fermenter Or can I just rack the finished beer out and dump thef new batch right in?
I’ve done it both ways, and haven’t had a problem with either method. Unless you have a massively high OG on the second batch, a whole yeast cake is probably a significant over-pitch. Not a huge issue, but beware of exploding fermenters… Ask me how I know…
The first time I did it, I cleaned the fermenter.
After that initial time, being somewhat lazy, I just wipe off the ring of gunk at the top with a paper towel soaked in starsan, scoop out part of the yeast cake, and dump the new batch in.
There are those that will say just dumping your fresh wort on a yeast cake won’t make the question if you get and infection, it will make it when. That said, it is about the only way I have ever done it other than saving some yeast in a mason jar then stepping it up in a starter.
Keep everything very clean on the first batch then dump the new wort in immediately after racking off the last batch.