Sparge Water Volume

First Question
I've been gearing up for my first all grain and looking over a bunch of recipes. Most of the time there are no details as to the volume of sparge water to use. I'm guessing that this has to do with the fact each system/technique is different. Please tell me if the following logic is correct for calculating the sparge water volume.

Working in reverse
Desired Volume in Primary
+ Volume Lost to Trub
+ Volume Lost to Evap (time x rate)
= Total Volume to Boil Kettle

Total Volume to Boil Kettle
- 1st Runnings Volume (Dough in volume - loss to grains - loss to deadspace)
= Sparge Water Volume

Second Question
Is there a minimum volume (ratio to amount of grain) recommended for the sparge? For one particular recipe with 16lbs of grain I calculated a sparge volume of 3.8 gallons using the logic above. Should I bump this up to a 90 min boil in order to get the sparge volume up to 4.5 gallons?

Thanks for the advice.

I think you've pretty-much gotthe first question down.

jayhoz said:

Second Question
Is there is a minimum volume (ratio to amount of grain) recommended for the sparge? For one particular recipe with 16lbs of grain I calculated a sparge volume of 3.8 gallons using the logic above. Should I bump this up to a 90 min boil in order to get the sparge volume up to 4.5 gallons?

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The answer is yes, but I can't tell you what the ratio is. I think a lot of brewers kindof do this by the seat of their pants. I mostly do moderate gravity brews, and I'm usually shooting for 7.5 gals in the kettle, which ends up being about 5.5 gals in the primary.

If that ratio gets too low, then you're not getting all of the sugars out of the grains. Fly spargers can just keep sparging until a certain SG (or pH) of the runnings is reached. For batch spargers, I think it's more of a seat of the pants thing.

16 lbs is about the biggest batch I've done--I collected about 8 gallons when I did a tripel with that amount of grain.

This: http://www.brew365.com/mash_sparge_water_calculator.php

Its been working well for me, but I think I need to lower my strike temps, I think I've been mashing on the high side of where I want to be. With this site I just get my recipe together, plug in the numbers, and write down my volumes, etc. Its worked well so far. Also, I batch sparge.

I have a couple of quick formulas I use for water needs. I use 1.1 qts/lb for my mash water (so 21 pounds of grain means I need, 23.1 quarts of water in my mash tun or 5.77 gallons). For sparge water, I use 1/2 gallon per pound of grain ( so for 21 pounds I'll need 10.5 gallons). I fly sparge and stop my runnings when I hit my preboil volume which for a 11 gallon batch, means I need a little over 13 gallons in the kettle. Using these numbers I have very little water left over in the MLT or HLT and hit my pre-boil volume without a problem.

If I do a step mash or decoction, I'll change the mash ratio to 1.4qts/lb.

Promash also has a handy water calculator that takes into account water losses in MLT deadspace, hoses, pumps, etc.

If you want decent efficiency and rinse most of the sugars out of the grain, you will need about 1/2 gallon per pound of grain. For 16 pounds of grain that's 8 gallons. add that to the 5 gallons or so for the mash and you end up with about 11 1/2 gallons in the brew pot. For a 5 gallon batch that equates to a LOT of boiling. If you are doing 10 gallons it is just about right.

RichBrewer said:

For 16 pounds of grain that's 8 gallons. add that to the 5 gallons or so for the mash and you end up with about 11 1/2 gallons in the brew pot. For a 5 gallon batch that equates to a LOT of boiling. If you are doing 10 gallons it is just about right.

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Aren't you going to get WAY different OG's by boiling the 11 1/2 gallons down to 5 gallons vs. 10 gallons? Am I missing something? The recipe would obviously be double from 5gal to 10gal. I'm probably missing something obvious, but I had to ask.