I am about to set about my first pressure fermented lager, and will be using a Fermzilla V3.

This has a large valve at the base of the conical pressure vessel leading into a small jar that can be shut off and removed.

When initially filling and starting the fermentation should I have this valve open or shut? (i.e. should the bottom chamber be full and open during fermentation)

2 Answers 2


I have never used one, but based on videos online like this one, you leave the valve to the collection jar open during fermentation.

This makes sense to me, since the purpose of the jar seems to be to collect the trub and remove it easily. Leaving it closed over an empty jar would just mean there is a bunch of oxygen ready to be introduced to your batch at the worst time.


I have never used one but on the basis of what I see online I would definitely leave it closed. The valve is apparently intended to dump the settled trub into the jar. When the fermenter is pressurized the pressure will help transfer the trub to the jar when the valve is opened. If you leave the valve open the jar is likely to fill with wort before the trub has settled. Also, a valve is better suited to retain pressure than a jar which I assume is removable so it can be emptied.

  • I've also seen people using the jar for dry-hopping without any oxygen exposure. So definitely keep it closed at first. Jun 18, 2023 at 9:42
  • I'm in 2 minds... the jar can of course be purged with CO2 before anything is done but the problem with both trub dumping and dry hopping in this way is when you open the valve a massive bubble farts up through the fermenter unsettling the trub and or top-floaters. I bought a top mounted dry hop-bong, great bit of kit. Jun 22, 2023 at 7:23

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