how much water to boil?

[KevStL]

I'm about a week away from brewing batch #2, which will be another kit (not sure which one yet - we'll see what mood I'm in when I go to the LHBS). The directions say to use 2.5 gallons to disolve the extract and boil the hops, but I've seen other places give the suggestions of anywhere from 1 gallon to as much water as your pot can hold.

I'm looking for reasons behind all the suggestions so I can determine which is the best option for me.

 

[ArcaneXor]

As much water as your pot can hold. Just compensate your bittering hop additions accordingly (reduce their amount by ~10% or add them a little later in the boil).

 

[FensterBos]

If you are doing extract, I would stick with 2.5 gallons. That should give you enough volume for your extract additions and hops.
There is no need to boil the full 5 gallons since it would be harder to chill after flame out. What I used to do is boil the 2.5 gallons and then put another 2.5 gallons in the freezer. When the boil was finished I would then add the icy cold water to the fermenter and the hot wort as my own way to chill the wort fast. Of course, you need to remember that you'll lose about 10% of the wort to evaporation, so you might need 2.75 gallons of water to reach the full 5 gallons.

 

[justinakajuice]

What works well for me is when I do those kits, I use 3 gallons of water for the boil, dump it over about 8 lbs of ice and fill with my sink hose squirter thingie until my temp and volume are right. Doing it this way, I can get an extract done in two hours flat. You are really busy in those two hours, but it's worth getting done faster. The ice lets you hit your cooldown temps immediately and without using an expensive wort chiller. 2 1/2 gallons always seems like it's just not enough water to me. I like the fact I can steep with more water volume, makes me feel like I'm getting more flavor out of the batch when I use 3 gallons to start.

 

[TheSeether]

Your method will be specific to your equipment.

My pot will boil 3.25gal (total 4gal) but for comfort's sake I keep it at 3gal throughout the boil.

My method is to boil 2gal and dump into my fermenter and let that sit in a cold water bath throughout the boil to bring it to room temps.

Then I figure out how many =<3lb DME additions I will be making. Let's say 8lbs of DE?M are going into this batch. This makes a total of 3X =>3lb DME additions (3lb, 3lb, 2lb). I stagger my DME additions to facilitate hop utilization and lessen the final color. So, for this example I am going to add 3 DME additions and I boil each addition individually in a separate pot using 1 quart of water so that it is fully dissolved and does not disrupt the boil when added to the boil kettle.

I also know through experience that my boil kettle will lose almost exactly 3 quarts of water over the course of a 60 minute boil.

So, if my target boil volume is 3gal and I am adding a total of 3qts with my DME additions but I will lose 3qts to evaporation then I will make my initial boil volume 3 gallons.

In this way, once the boil is complete there are 3 gallons in the kettle and 2 cooled gallons in the fermenter. I can get my kettle down to 80F in 15 minutes using a circulating ice water bath in the sink. Dumping the kettle into the fermenter gets the whole 5 gallons down to room temps and aerates the wort (although I whip it with a whisk, too).

I keep an eye on my boil kettle because I know where the 3gal line is (you can scratch it in if you need to) and adjust additions as needed to keep a 3 gal volume. At any rate I always nail exactly 5 gallons into the fermenter unless I'm specifically shooting for a different volume.

As you can see, your equipment and your method will dictate exactly how you go about hitting target fermenter volume.