Ferment bigger volume than kettle volume

[tubbsy]

Brew day tomorrow and I'm making a simple session pale ale. I want to make a bigger batch than normal (28 or 30L), but my kettle (T500 boiler) only has a capacity of 25L. Using Brewers Friend recipe builder, if I use the upper volume to calculate ingredients, can I use less water in the mash/boil then top up the fermenter with cool water after chilling? Seems like I could, but wanted to check if there could be any issues.

 

[MHB]

Mostly yes, there are issues with what is called "Over Gravity Brewing". A lot of big brewers do it to get more beer out of their equipment, but they are tending to be brewing at 30%+ over gravity, any more and there are some real problems keeping the beer tasting the way they want, mostly the way it did before they got greedy.

In your case going from 25 to 30L is only 16% bigger so there wont be too many problems flavour wise.
When it comes time to dilute your liquor (water) must be Chlorine free, Sterile and De-Aired (oxygen free).
At a home brew scale I would boil some water and no-chill it (seal it up in an airtight container) that should see you clear as far as your diluting water goes.

Remember that bigger beer needs more yeast; tends to darken faster in the kettle; is more prone to showing yeast stress... So lots of good healthy yeast, keep the ferment cool and follow good brewing practice.
Mark

 

[tubbsy]

Thanks Mark. I'm targeting a post dilution gravity of 1.041, so before diluting will only be around 1.054, so not too big.

Will boil up the water tonight and chillit down.

 

[S.E]

can I use less water in the mash/boil then top up the fermenter with cool water after chilling?

Yes you can. The water doesn’t need to be oxygen free, I think Mark may be getting confused with adding water to beer rather than to wort you are about to ferment? Same as adding water to beer kits.

If you have a chiller you could just boil up the liquor and chill it into the fermenter straight on to the wort.

 

[MHB]

You might be correct, I was referring to a post fermentation addition.
If being diluted before fermentation, then de-airing wont be necessary.
Mark