Effect of Diluting on OG

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

wort_up

Member
Joined
Dec 17, 2009
Messages
11
Reaction score
0
Location
Santa Barbara, CA
I only have a 5 gallon stockpot and wish to make a 5 gallon batch. How much will it affect my OG by boiling with 4 1/2, then diluting with a couple gallons after the boil?

What if I boiled a couple gallons on the side, adding proportional amounts of hops to both? Thanks!
 

Pappers_

Moderator
Staff member
Mod
Lifetime Supporter
Joined
Jan 31, 2009
Messages
17,527
Reaction score
3,978
Location
Chicago
Hi Wort -

What you are describing is a common technique for brewers using malt extract. Do a 3.5 gal or so boil and top off with water in the fermenter. Lots of brewers do this.

Compared with doing a "full" boil, you will get lower hops utilization and have a greater chance of carmelizing the wort.

Cheers!
 

mrfocus

Well-Known Member
Joined
Oct 3, 2007
Messages
573
Reaction score
3
Location
Montreal, Canada
Remember, typically you want 1.5 what your boiling as a boil kettle. So if you have a 5 gallon BK, you can only do about 3.5 gallons comfortably.

Your best bet is to have 2 boil kettles, even if not the same size.
 

HotbreakHotel

Well-Known Member
Joined
Nov 14, 2007
Messages
351
Reaction score
3
Location
Grand Rapids, MI
If your post boil volume is 4 gallons, and you add another gallon after, your new gravity will be .8 of what it was before.

For example, if your 4 gallons has gravity 1.050, and you add a gallon of water your gravity will become 1.040, because 50*.8=40. If your 4 gallons has gravity 1.070, it will become 70*.8=56, or 1.056 after adding another gallon.

For other dilution ratios, the multiplier is (volume before diluting)/(volume after diluting).

As far as the way you're describing doing the hops, it seems like the hop utilization would even out. I think it's a good idea!
 
OP
wort_up

wort_up

Member
Joined
Dec 17, 2009
Messages
11
Reaction score
0
Location
Santa Barbara, CA
Pappers - This is my AG batch, hence the reason I'm using the technique. Seems to make a bit more sense with extract.

Hotbreak - Thanks for the numbers. I understand the math, I was just wondering about how much it would affect the OG not having the last couple gallons of sparge water (which would be pretty dilute anyway). The gravity of the boil would be higher than expected, compensating some for the dilution.

I think I will try the 2 pot method and do my best to have equally concentrated wort in each pot. Wish me luck. Thanks everyone for your help!
 

ArizonaDB

Well-Known Member
Joined
Feb 22, 2009
Messages
134
Reaction score
1
Location
Flagstaff
Wort Up,

I have always done just what you described in your OP. I have a 5gal stock pot that I use to mash and sparge (using the brew-in-a-bag/stovetop brewing method). I've found that my limit is about 10lbs of grain to comfortably mash and sparge in my 5gal pot. And even though this wont allow you to do some of the bigger beer styles out there, you can still manage many different types of styles. I use this website to calculate if I have enough room to mash a certain amount of grain:

http://www.rackers.org/calcs.shtml

I've done up to 11.5lbs of grain but with much spillage, unfortunately. So I decided I would stick to a max of 10lbs and top off my gravity with DME if needed. I can easily make a low ABV blond or wheat ale with under 10lbs of grain.

I've thought about using more water and splitting the runnings into two equal amounts and boiling them separately but it seemed like too much trouble when I was already getting good results. Keep in mind, you will get less efficiency by using less water, so keep some DME on hand, just in case.

Good luck. After a few batches you will have your system down and be making some great beers, if you aren't already.
 

homebrewpey

Active Member
Joined
Dec 7, 2009
Messages
36
Reaction score
1
Location
Seattle
I agree with ArizonaDB on the last post.

However, just to eliminate undue headache and make things easier on yourself, I suggest you buy a larger pot, such as a ten or 12 gallon pot for your batches. You can find one reasonably cheap on craigslist and it will allow you to make larger batches in the future and prevent boilovers.

I found two large kegs with spigots and false bottoms on craigslist for $200, but you could likely find one for under $100 or even less if you're willing to go without the false bottom.

Just my $0.02.
 
OP
wort_up

wort_up

Member
Joined
Dec 17, 2009
Messages
11
Reaction score
0
Location
Santa Barbara, CA
Thanks for the input. After a bit of time searching, I found a cheap 32 quart tamale steamer for $20. Not the best brew kettle but its a start.

Now on to conquer the next issue... water :eek:
 

ArizonaDB

Well-Known Member
Joined
Feb 22, 2009
Messages
134
Reaction score
1
Location
Flagstaff
Wort,

Care to share where you found said tamale steamer? I have been searching for a cheap 30+qt pot for brewing and haven't found anything for cheaper than about $48.
 
Top