Cooling the wort

I do partial mash brews using bottled spring water. The boil is usually ~3 gallons, and then I top it off to 5.25 gallons in the primary bucket.

I have a pre-chiller and immersion chiller that I use to cool my wort, which usually takes about 15 minutes to get from boiling to 76F.

I was thinking that since I use bottled water, I could potentially refrigerate a gallon, and then add it to the wort as it's cooling to help speed up the cooling process. Maybe once the wort hits the upper 80s, I could slowly add some refrigerated bottled water to get it down to the mid-70s. Is there anything wrong with doing this?

thats what i do. I actually throw two whole gallons in the freezer the morning that i start my brew day and by the time its wort cooling time, i use my immersion chiller as well as those really cold gallons and BOOM (literally, there is an explosion) my wort is chilled to ~70.

nothing wrong with that. You can even do a little math to figure out how much cold water you need so that you don't cool the wort down too much.

JLem said:

nothing wrong with that. You can even do a little math to figure out how much cold water you need so that you don't cool the wort down too much.

Click to expand...

Do you have that formula JLem?

MisterGreen said:

Do you have that formula JLem?

Click to expand...

Sure thing - it's really just a weighted average.

Final Temp = (Volume of wort x temperature of wort) + (Volume of cool water x temp of cool water) divided by total volume

SO if you have 2 gallons of 120F wort and top off with 3.5 gallons of 40F water, you'll end up with 5.5 gallons at 69F.

Give or take a few degrees to account for some heat absorbed by the fermenter.

Sweet, I'm gonna try this today with a brew. I expect to have it chilled in under 10 mins.

JLem said:

Sure thing - it's really just a weighted average.

Final Temp = (Volume of wort x temperature of wort) + (Volume of cool water x temp of cool water) divided by total volume

SO if you have 2 gallons of 120F wort and top off with 3.5 gallons of 40F water, you'll end up with 5.5 gallons at 69F.

Give or take a few degrees to account for some heat absorbed by the fermenter.

Click to expand...

Very helpful, thanks!

I'm brewing saturday and going to do this + freeze some water after i boil it before hand to throw directly into the wort -

http://www.howtobrew.com/section1/chapter7-4.html

^That is what John Palmer has to say

edit: thanks Jlem! that is awesome.

JLem said:

Sure thing - it's really just a weighted average.

Final Temp = (Volume of wort x temperature of wort) + (Volume of cool water x temp of cool water) divided by total volume

SO if you have 2 gallons of 120F wort and top off with 3.5 gallons of 40F water, you'll end up with 5.5 gallons at 69F.

Give or take a few degrees to account for some heat absorbed by the fermenter.

Click to expand...

Thanks for this. I throw my water in the freezer too so this helps a lot.