Temps of wort/cold water mix

I do 2 gallon boils w/LME. Room temperature water is around 75 deg (tap water the same) so I've drawn 5 gal of RO water and put 3 gal in the fridge. They are at 40 deg. Question: is there any kind of calculation about what temp to bring the wort down to mix with 3 gal 40 deg water to get around 70 deg in the fermenter?

Tw = ((Mt *Tf) - Mc * Tc)/ Mw

Where:
Tw = temperature of wort
Mt = Total volume/ mass (works the same either way) - 5 gal
Tf = Final desired temperature - 70^F
Mc = Volume/mass of cold water - 3 gal
Tc = temperature of cold water - 40^F
Mw = Volume of wort - 2 gal

Tw = ((5 gal * 70^F) - 3 gal * 40^F) / 2 gal

Tw = 115^F

Are you trying to pour the super hot wort into extra cold water?
I suggest you read up on Hot Side Aeration, and decide if you still want to pour hot wort around.

malkore said:

Are you trying to pour the super hot wort into extra cold water?
I suggest you read up on Hot Side Aeration, and decide if you still want to pour hot wort around.

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The question was: to what temp to cool the wort to to hit 70 deg when poured into 40 deg water. Bill's brew gave a formula which yielded 115 deg. Is this still super hot wort?

since you didn't search about hot side aeration....

any time you splash the wort and its warmer than 85-90 degrees, you're running the risk of oxidizing your precious beer before its even beer.

cold water baths, or wort chillers are the proper way to cool the wort prior to pouring it into the fermenter.

malkore said:

since you didn't search about hot side aeration....
any time you splash the wort and its warmer than 85-90 degrees, you're running the risk of oxidizing your precious beer before its even beer.
cold water baths, or wort chillers are the proper way to cool the wort prior to pouring it into the fermenter.

Click to expand...

Gotcha malkore. the chilled water was, I thought, a bright idea contrary to my practice for the 10-12 batches I've brewed. I have my mix water and cooled wort temps recorded someplace but recall that I generally cool the wort to around 90 deg to hit my 70 deg or so. I thought I'd make my cooling job easier. I have taken my chilled water out of fridge and is now on the way to room temp. I'll be brewing a "Mild" the next day or 2 and then a corriander wheat.

I don't agree with some of the HSA comments.

I've been pouring my hot wort through a nylon net for EVERY BATCH over the past 14 years. I don't recall experiencing hot side aeration problems when pouring hot wort.

I will admit that I did have problems/bad brews when I tried cooling the brew some, like between 90 and 140 then into the net. Lessons learned...

I don't do that anymore. It's straight from the boil pot to the primary through the net for me.