Adjusting final beer with water equation help

[safedude]

For various seasons (low volume turnout + too high abv) could someone shed some light on how to calculate a new abv if I were to add water to my finished beer? And the same deal with ibu?

It's an APA at 32 ibu and 6% abv at 4 gallons. I was playing around with my newish conical and got trigger happy with the ball valve. 2 too many trub dumps I'd say. I lost 2 gallons. However!.. It tastes too strong for my liking (attempted to make a light pale) and I want to see the effect 1 gallon of sterilized water has on it. It will be kegged today.

Can someone help me with calculating the new abv and ibu? Or post up the equation (if there is one) and I'll take a stab at it.

Thanks!

 

[BrewCityBaller]

I can help with ABV. For example, if you have 5 gallons to start and 6% ABV then you have (0.06)(5) gallons of ethanol, or 0.3 gallons. If you added a gallon of water, you would still have 0.3 gallons ethanol, but now your ABV would be (0.3)/6, which would be 5% ABV. You can do this with any ABV and volumes.

I am confused by your numbers though. Did you start with 6 gallons, lost two gallons, so now you have 4 gallons of beer. And now you want to add 1 gallon water to bring it up to 5?

If that's the case then the new ABV of your 5 gallons of beer is 4.8% ABV.

The formula for this is [(Original ABV)*(Original Volume)]/(New Volume)

FYI if you add a gallon of water to four gallons of finished beer I think you're going to get something very, very thin in the body department.

 

[safedude]

Thanks! This is exactly what I was looking for. I didn't realize how simple it was.


Yeah, I had 6 gallons of fermented beer, but I lost 2 gallons from messing with the valves too much.

 

[BrewCityBaller]

Thanks! This is exactly what I was looking for. I didn't realize how simple it was.


Yeah, I had 6 gallons of fermented beer, but I lost 2 gallons from messing with the valves too much.

Super simple! So your new ABV would be 4.8%