# Amount of Water to Boil for Wort

If I'm making a 5 gallon batch of beer, how much water should I use for my wort? Papazian's book says to use 1.5g and add it to 3.5g of room temperature water already in the carboy. I see how this would be helpful because it would help to cool the wort down quicker to pitch, and I wouldn't have to worry necessarily about the glass breaking. I've also seen other resources (including something, I think, through this site) recommending that for a 5g batch you boil all 5g in your wort. What are the pros and cons of the latter method? Thanks in advance

-

Okay, well there are a few things to consider.

1. How big is your pot? If you don't have the headroom to handle the inevitable foam, you will have a mess.

2. Can you easily chill five gallons of wort without using a cold water additive? If you don't have a wort chiller, this can be a big issue.

3. The amount of wort you boil, the specific gravity of that wort, and when you add hops will greatly vary the bitterness you obtain.

A simple beer with 6lbs of light DME, 1.5oz of Norther Brewer hops @60min and .5oz of Saaz at 1min in a three gallon boil gives us 34.4 IBU.

If you change ONLY the boil size, to five gallons, the IBUs go up to 47.3. Fermentables, boil size and hop AA can all effect the final bitterness. I recommend using software or something like Beer Calculus (free, online) to adjust your recipe to the boil size you want. So in short, it does matter how much you boil and you have to adjust your recipe to account for it. Or you will miss your IBU targets.

-
Got a 5g pot and no wort chiller. I might do a 3g boil and see how that goes. Thanks for the info on Beer Calculus! – WhatsBillDoing Dec 27 '09 at 21:53

Doing a full-wort boil (all 5 gallons) offers a few technical advantages over partial-wort boils. There are a number of reactions that depend on the concentration of wort.

First, the wort-darkening reactions are more pronounced at a smaller volume meaning your wort will come out a little darker than you expect.

Second and more importantly, the rate of hop utilization is diminished in a partial-wort boil. You may have to use more hops to get the desired bitterness level. Most brewing software takes boil volume into account when calculating IBUs. In rare cases of high bitterness, small wort boils the wort can become saturated with iso-acids, putting a cap on IBUs.

The biggest drawback to this method is the extra equipment you need. A good heat source and a chiller are important.

Partial-wort boils are convenient, and for the most part, you will make fine beer without a full boil. I recommend you sterilize the added water by boiling and cooling (maybe overnight).

-
Is it really necessary to sterilize the room temp water not included in the boil? I have never done this and have not had issues in the past. – Jordan Dec 27 '09 at 17:20
I hate to throw out 5 gallons of beer. City water is probably pretty full of chlorine or chlorimate, but boiling is the best way to kill the nasties. Your water may be clean but the pipes could harbor microorganisms. – Dean Brundage Dec 27 '09 at 17:27
What if I use bottled drinking water? – Jordan Dec 28 '09 at 4:51
Even then, I recommend boiling. – Dean Brundage Dec 29 '09 at 0:27

If you have a wort chiller, boiling the entire batch is easier. If not, adding cold water is easier. That's about the biggest difference.

-
Yeah, without the wort chiller a full boil just seems silly. Is it better to buy or build one? – Jordan Dec 27 '09 at 17:22
I just did an all grain batch over the weekend and used a tote filled with 30lbs of ice and a few gallons of water with added salt. My kettle was about 3/4 submerged and I got it to go from boil to 95*F in about 10 minutes. This method has worked wonderfully for me, and I have never used a wort chiller that can be bought from the home brewing supply store. For larger batches (I have a 10gal kettle) I could see this being problematic, though. – jsmith Aug 6 '12 at 19:16