I'm relatively new to homebrewing. I've just done my 5th batch a few days ago. I came across the term partial boil when watching a homebrew video on kettles.

I'm not quite sure if what I do is considered a partial boil, here's my all grain BIAB process. I use a 20 litre

Bring 8 litres to 74 degrees C. Add the bag of malt and the water lowers to 68 degrees C Sparge and reach the boil volume in the kettle of 14 litres Start 60 minute boil where volume lowers to 11l (the fermenter target) Add hops etc Cool Rack and pitch yeast

Is this a partial boil? My confusion is that there seems to be a lot of talk around the subject of 18-20 litre kettles not being able to do full boils.


2 Answers 2


Partial boil refers to when you boil a certain volume of wort smaller than the desired batch size, then top off the fermenter to reach the full volume. This is often done when you have smaller pot for boil than for fermentation. For instance when I started brewing I would boil about 10 liters then top off to 19. Partial boils can affect hop utilization (drops) and IMO flavor. Here’s a blog post on it. Partial boil effects

  • 1
    Cheers! Would what I'm doing be considered a full boil?
    – BarryWalsh
    Feb 22, 2018 at 9:40
  • I don’t think so. You aren’t adding extra water to the fermenter to reach your batch size.
    – uSlackr
    Feb 22, 2018 at 15:54

Partial boil is a method of boiling a concentrated version of your wort, then adding this wort and new water to the fermentor to get your desired volume.

For example it's a way to get 5 gallons of beer in a single brew with a 3 gallon pot. So you would boil 2.5 gallons wort with an OG twice what the recipe calls for then mix it with 2.5 gallons of water to get your 5 gallons of wort.

In your case if the desired end volume is 11L and doesn't call for water blending. Then your brew is full boil, not partial.

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