I've recently tried extract brewing after all grain brewing. Strange I know, but I wanted to eliminate the mash part of the process to see if it help get rid of a off flavour (it did but that will be another question).

I did a small batch so I boiled the whole batch, but I see in most recipes they tell you to do a small amount then add cold water before fermenting.

This baffles me. Everything I read about brewing stresses the importance of sanitation, including not getting anything unsanitised into contact with the post-boil brew, including cold water. The existence of no-rinse sanitiser shows how important this is.

So how is it that I am now being asked to add a whole load of cold water to the post-boil wort?

  • can anyone help me?? i messed up the instructions on my malt extract home brew, and didn't add enough water. the set up should be 9 liters iv only got 4 liters in the brew i forgot to add the last 5 liters of cold water before adding the yeast. it been brewing now for about 12 hrs. can i just open the fermentation lid and pour the rest of the water in now or is it to late? May 13, 2020 at 23:26
  • Please start a new question if you have a question to ask May 14, 2020 at 21:28

2 Answers 2


Sanitation is paramount. That said, these are normal instructions for most early brewers. Mostly its because when people get started its assumed they don't make an investment in 8 gallon pots (probably because most stovetops will never boil a full 5 gallons).

Most municipal water supplies have very low microbial contamination. When coupled with an adequate yeast pitch most of the time it all works out.

So while it makes most of us "experienced brewing know-it-alls" cringe... it works for most new brewers. I know I never had a problem with topping off straight from the sink. Otherwise, most new brewers wouldn't get past the first batch in the hobby. If it concerns you and you have the equipment for it then boil and chill some tap water the day before.


While they say to add cold water, this is water that han been boiled and chilled.

The dilution method does two things, allows a larger batch size than your boil pot capacity and helps cool the wort for pitching.

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