Caleb MorganBy Caleb Morgan

Updated November 2026

The best time to dump yeast from a conical fermenter is after primary fermentation has finished, gravity has held steady for at least two days, and the trub has settled into the cone. Dumping at that point gives you a clear beer with less off-flavor risk, and it keeps your yeast from sitting on the cake longer than it should. This guide walks through how to read your fermenter, pick the right window, and make the dump without losing good beer.

Confirm Fermentation Is Actually Finished

Dumping too early leaves fermentable sugar behind, and dumping too late can let the yeast autolyze and add harsh, meaty flavors. Start by taking a gravity reading with a hydrometer or refractometer (with a correction for alcohol if you use a refractometer). Wait 48 hours and take a second reading. If both readings match, fermentation is done.

Shopping for one? See our guide: FastFerment Conical Fermenter 7.9 Gallon Review (2026).

Also look at the krausen and airlock. A quiet airlock is a useful hint, but it is not proof on its own, since temperature swings and CO2 pressure can fool you. Trust the gravity readings first.

Give the Yeast Time to Clean Up Diacetyl

For ales, a short diacetyl rest often helps. Raise the fermenter to about 66 to 68°F for 24 to 48 hours once gravity is near final, and let the yeast reabsorb diacetyl before you cool and dump. Lagers usually benefit from a diacetyl rest as well, but follow the strain’s guidance on temperature. This step is worth doing on the same day you confirm stable gravity.

Cold Crash, Then Dump

Cold crashing drops the temperature so yeast and trub compact in the cone. Chill the fermenter to near freezing over 12 to 24 hours, then hold it there for 24 to 48 hours. A colder cone means a tighter, easier-to-release trub layer. Keep the vessel sealed and under gentle positive pressure to avoid oxygen pickup while it is cold.

How to Make the Dump Step by Step

Once the beer is cold and clear at the bottom, follow this sequence:

  1. Purge the valve and tubing with sanitizer, then flush with fresh water.
  2. Connect a clean hose to the bottom valve and place the other end in a sanitized collection vessel or drain.
  3. Open the valve slowly and let the first few ounces of yeast and trub run out. Close the valve as soon as you see clear beer.
  4. If you plan to harvest yeast, collect the slurry into sanitized jars before you dump the trub.
  5. Transfer the beer to your keg or bottling bucket with a closed transfer, avoiding splashing.

If you are unsure how much yeast to keep, the process for capturing a usable slurry is covered in detail in How to Harvest Yeast from Fermenter: A Step-by-Step Guide for Homebrewers. For the mechanics of the valve and cone, Conical Fermenter Yeast Dump: A Step-by-Step Guide for Homebrewers goes deeper.

Timing Checklist

  • Gravity stable for 48 hours
  • Diacetyl rest completed (ales and many lagers)
  • Cold crash held 24 to 48 hours
  • Sanitized hose, valve and collection vessel ready
  • Oxygen exposure kept minimal during transfer

Common Mistakes

  • Dumping before gravity has stabilized, which leaves residual sugar and risks bottle bombs.
  • Skipping the cold crash, so trub stays loose and the dump pulls more yeast into the beer.
  • Letting the yeast sit for weeks past completion, which can add autolysis flavors.
  • Opening the valve too fast and sending a rush of trub into your keg.
  • Forgetting to sanitize the valve before the dump, which invites infection.

A clear sanitized hose and a sturdy valve make the dump cleaner and easier to control. Look for a food-grade silicone or braided tubing sized to fit your fermenter’s outlet. A refractometer also helps you confirm stable gravity without opening the vessel.

  • Food-grade silicone tubing for fermenter dumps: flexible, easy to sanitize, and fits most conical outlets. View on Amazon
  • Refractometer for brewing: lets you check gravity with only a drop of sample, reducing oxygen exposure. View on Amazon
  • Sanitizer spray bottle for valves and fittings: useful for quick sanitizing before every dump. View on Amazon

FAQ

How long should I wait after cold crashing before dumping yeast?

Most homebrewers hold the cold crash for 24 to 48 hours before dumping. That window is usually enough for the trub to compact without over-chilling the beer.

Can I dump yeast while the beer is still fermenting?

No. Dumping during active fermentation removes the yeast needed to finish the job and can leave the beer sweet or unstable. Wait until gravity is stable.

Is it safe to leave yeast in the cone for a few extra days?

A few extra days on the cake is usually fine, especially for ales. Several weeks is a different story, since autolysis can add off-flavors. If you are unsure, consult an experienced local homebrew club or a professional brewer for advice.

Conclusion

Dump your yeast once gravity has held steady, any diacetyl rest is complete, and the beer has been cold crashed long enough for the trub to compact. Use a clean, sanitized hose and open the valve slowly so you keep the beer clear. Follow those steps and your beer will reach the keg or bottling bucket in better shape.

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Caleb Morgan

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our home brewing guides, checking product details against manufacturer specifications and owner feedback.