Brewing a double batch & diluting prior to fermentation

[Chris112]

Wondering if anyone has done this or if it's advisable or not but I am wanting to brew a double batch of a pale ale to do some testing with my keg system (hear me out) and if it works out then I could have a process for making a double batch of anything that's not a super high gravity beer. I basically want to test two separate kegs with an identical beer and rather than mash and boil two separate times (which would be an almost 8 hour day), I thought I could try to mash and boil a very high OG beer, then dilute and split into two fermenters. I've got a 3v 5 gallon system and have only done one very high OG beer and I added DME to boost the gravity.

Thoughts?

 

[T Murph]

It can definitely be done. Just make sure your calculations are good or you may end up with budlite. I have done second runnings off a big beer mash and added DME to get the OG up to where I needed it. That works well but can easily turn into a ten hour brew day.

 

[AlexKay]

High gravity brewing followed by dilution is how (many of) the pros do it (though usually dilution occurs right before packaging, not before fermentation.) Efficiency and hop utilization may suffer a little bit, but you should be fine. Since I'm not exactly sure what you're doing ... why not make a standard batch, ferment in a single fermenter, and then half-fill two kegs?

 

[CascadesBrewer]

Thoughts?

After recently upgrading my 10 gallon kettle to a 15 gallon one, I have been debating about something like this, or about trying to get a full 5 gallon batch out of my normal 2.5 gallon batch system.

The calculated gravity needed is a straightforward linear equation. Say you want 10 gallons of a 1.050 beer you need 500 gravity point (10 x 50 = 500). Divide those gravity points by the volume of undiluted wort to figure your target gravity:

• 8 gals = 1.063 (500 / 8 = 62.5)
• 6 gals = 1.083 (500 / 6 = 83.3)
• 5 gals = 1.100 (500 / 5 = 100)

The larger batch you can produce, the lower gravity needed, and the better efficiency you will get.

There might be some impact on hop utilization with the more concentrated boil.

 

[Joshua Hughes]

I used to do it a lot. I just upped my IBUs and it turned out fine. Kettle space was my issue

 

[SanPancho]

theres definitely a change in hop utilization, but any decent calculator should be able to get you the right dose for your desired IBUs.

the biggest issue is when you plan to dilute. if you do it at pitching time, then its alot easier. if done post ferment, you've got other issues. namely, trying to get the same/desired yeast profile out of a high OG beer vs a normal OG beer. you've also got to make sure you're adding deoxygenated water or else you've just dumped a bunch of dissolved o2 into your beer.

if you dilute the wort before yeast pitch you're in a better position. in that case an argument could be made for not using deoxygenated water, although i would personally only do that once my yeast were active and would uptake that dissolved oxygen asap. but worst case, you oxidize and lose some of your kettle hops, but can still "cover it up" with dry hops.

as always in brewing, there's tradeoffs.

 

[Joshua Hughes]

To follow up I even did it as a parti-gyle cheat. I split into 2 small car boys and added water to one to get an ordinary bitter in one and stronger bitter in the other.

 

[BrewnWKopperKat]

I used to do it a lot. I just upped my IBUs and it turned out fine. Kettle space was my issue

What OG did you target going into the kettle?

 

[Joshua Hughes]

Can’t remember been 2 years when I was working with a small kettle. I think I aimed for 1.050 in carboy 1 and added water to hit about 1.035 in the other or something like that. A 5% and 3.5% if I remember correctly

 

[Chris112]

High gravity brewing followed by dilution is how (many of) the pros do it (though usually dilution occurs right before packaging, not before fermentation.) Efficiency and hop utilization may suffer a little bit, but you should be fine. Since I'm not exactly sure what you're doing ... why not make a standard batch, ferment in a single fermenter, and then half-fill two kegs?

Thats a good idea and I might try it. My issue I am trying to fix is that I have two brand new torpedo kegs that start out pouring fine, and then about halfway through the keg (after about 2 weeks) I get surging foamy pours. It will pour clear for a second, then foamy, then clear and then all foam. I've been working through the issue and I think I have isolated it to just those two kegs. I've changed pressures, swapped lines, cleaned all the lines, cleaned the faucets, checked the chiller system, etc. I have two other used 5 gallon kegs that lasted a month+ without any pouring issues.

The split batch would be with one of those kegs and another one just so i can have the same exact beer, carbed to the same level so I can compare just the kegs.

 

[CascadesBrewer]

To follow up I even did it as a parti-gyle cheat. I split into 2 small car boys and added water to one to get an ordinary bitter in one and stronger bitter in the other.

This has been a thought of mine as well. It would be cool to get a Pale Ale + IPA, or Single + Trippel, or Strong Bitter + Ordinary Bitter. Did you find that the hop bitterness and hop flavor/aroma was on par between the different gravity beers?

 

[doug293cz]

Wondering if anyone has done this or if it's advisable or not but I am wanting to brew a double batch of a pale ale to do some testing with my keg system (hear me out) and if it works out then I could have a process for making a double batch of anything that's not a super high gravity beer. I basically want to test two separate kegs with an identical beer and rather than mash and boil two separate times (which would be an almost 8 hour day), I thought I could try to mash and boil a very high OG beer, then dilute and split into two fermenters. I've got a 3v 5 gallon system and have only done one very high OG beer and I added DME to boost the gravity.

Thoughts?

You will take an efficiency hit going the dilution route. The hit comes from lower lauter efficiency. I have run simulations (using my spreadsheet), that quantifies this lauter efficiency loss.

Here are the parameters:

OG target to fermenter​	1.040​
Mash thickness​	1.5 qt/lb​
Weighted average grain potential​	1.037​
Sparge​	Triple batch or fair quality fly sparge​
Conversion efficiency​	100%​
Total boil off​	1.0 gal​
Target fermenter volume​	5.5 gal​
Kettle trub​	0.5 gal​
Post boil volume target​	6.0 gal​

In the case of the diluted batch we need to put 2.25 gal of 1.080 wort in each fermenter, and dilute with 2.25 gal of water.

For the non-diluted case, it requires 7.0 lb of grain for each batch (14 lb total), and results in a lauter efficiency of 97%. For the diluted case, the lauter efficiency drops to 81.8%, and total grain required grows to 16.6 lb.

If we want an OG of 1.050 then the numbers change to: Undiluted case - 17.8 lb of grain and 94.8% lauter efficiency, and diluted case - 23.8 lb of grain and 71.5% lauter efficiency.

So, the efficiency hit of brewing a bigger beer and diluting is not so bad for low OG beers, but gets much worse with increasing target OG.

If your conversion efficiency is less than 100%, then the loss of loss of lauter efficiency between the 2X undiluted vs 1X diluted cases is even more than above.

Brew on

 

[Joshua Hughes]

This has been a thought of mine as well. It would be cool to get a Pale Ale + IPA, or Single + Trippel, or Strong Bitter + Ordinary Bitter. Did you find that the hop bitterness and hop flavor/aroma was on par between the different gravity beers?

The weaker beer was less bitter but was in line with what I figured

 

[Red over White]

High gravity brewing and diluting in the fermenters works fantastic. For all grain brews only consider diluting up to 40% without taking a hit in the flavor department. I add all salts to the strike water and dilute with chilled distilled water in the fermenter for the final water profile. If you calculate hop IBU's for the end kettle volume high gravity and diluted volumes separately, they will be very similar amounts of hops on lower IBU beers and be quite smooth for bittering addition only beers.

With the OP's system you would need to boil in 2 separate kettles and adjust the combined boil off rate with shorter boils or less vigorous boils, either works.

 

[Chris112]

You will take an efficiency hit going the dilution route. The hit comes from lower lauter efficiency. I have run simulations (using my spreadsheet), that quantifies this lauter efficiency loss.

Here are the parameters:

OG target to fermenter​	1.040​
Mash thickness​	1.5 qt/lb​
Weighted average grain potential​	1.037​
Sparge​	Triple batch or fair quality fly sparge​
Conversion efficiency​	100%​
Total boil off​	1.0 gal​
Target fermenter volume​	5.5 gal​
Kettle trub​	0.5 gal​
Post boil volume target​	6.0 gal​

In the case of the diluted batch we need to put 2.25 gal of 1.080 wort in each fermenter, and dilute with 2.25 gal of water.

For the non-diluted case, it requires 7.0 lb of grain for each batch (14 lb total), and results in a lauter efficiency of 97%. For the diluted case, the lauter efficiency drops to 81.8%, and total grain required grows to 16.6 lb.

If we want an OG of 1.050 then the numbers change to: Undiluted case - 17.8 lb of grain and 94.8% lauter efficiency, and diluted case - 23.8 lb of grain and 71.5% lauter efficiency.

So, the efficiency hit of brewing a bigger beer and diluting is not so bad for low OG beers, but gets much worse with increasing target OG.

If your conversion efficiency is less than 100%, then the loss of loss of lauter efficiency between the 2X undiluted vs 1X diluted cases is even more than above.

Brew on

Good info, thanks!