Calculating Runoff

I've been here a while lurking around and did my first PM a few weeks ago. One thing I can't Fully grasp before doing my next PM and moving on to AG this summer, is how do you calculate how much wert you should be able to collect from a grain bill? I am only doing 5 gallon batches right now and was confused during my first PM. I just did two runnings. I had 3 lbs of grain. Ran 2 batches of 1.125 gallons of sparge water. using teh 1.375quarts/lb thinking. is this correct? If so does this mean you need to need to plan your grain bill to match your grain water ratio for what size boil you want to do? I think I may be finally realizing this as I'm typing it. Or am I wrong.

Experience, a.k.a., "trial and error" often is the best educator here, and preparation for the unplanned is the best planner.

ProMash and my own experience give me a pretty good idea as to how much water I need and how much wort I will get from my mash and sparge. However, I never quite know how it will work out. Plan your mash according to your desired grain/water ratio and just see what your runoff is.

I batch sparge, so I just measure the volume of my first runnings and figure out hpw much I need for my sparge. However, since I want to start heating and treating my sparge water well before my first runnings are collected, I always prepare extra water for sparging. The plants don't mind if they get a little extra drink at the end of the day.


TL

This is pretty easy if you're batch sparging, once you dial in a few variables. Basically, you need to know how much dead space you have in your mash tun and how much water your grain will absorb (for me, about 0.2 gallons per pound). BeerSmith tells me how much water I need to infuse to hit my mash temp. Starting with that, I subtract dead space, subtract how much the grain is going to absorb, and I know how much total sparge water I need to run through to add up to my desired boil volume. I'll then split the sparge additions up so that the total volume I'm collecting from each sparge is just about the same.

Pounds of Grain 12.00
Quarts per Pound 1.25
Total Strike Water 15.00

Desired Boil Volume 30.00

Strike Water 15.00
Less: Dead Space 0.00
Less: Grain Absorption (0.2 gallons/lb)(9.60)
Water Collected From Mash 5.40
Needed From Sparge 24.60

Added Before Taking First Runnings 9.60
Collected From First Runnings 15.00
Collected From Second Runnings 15.00

Here's how I guestimate it. I figure out the gravity I'm looking for at a given volume. Then I work backwards based on my system efficiency (based on experience/experimentation) and grain bill's extract potential to get the amount of grains.

For example, if I'm trying to hit 1.050 at 5 gals, I'm shooting for 50pts*5gals = 250pts of sugars total. 1 lb of sugar has 46pts of potential. Since I usually get around 70% efficiency and my grain has an extract potential of say 80%. I have:

W*46*80%*70%=250pts, where W is the amount of grains I need in lbs

Solve for W= (250/46)/(80%*70%) gives me 9.7lbs of grain.

Then I sparge to collect enough run off to make my target volume plus estimated boil off volume and grain absorption.


Using the example above, I figure for .12 gals/lbs of grain of grain retention and about 1 gal of boil off during the boil so I'd have a combined mash and sparge water volume of 5+.12*9.7+1=7.2 gals.

This usually works out to around to 2.5-3 qts per pound of grain for normal gravity beers. Hopefully, if my efficiency is consistent with what I predicted, I end up hitting my target gravity at target volume. Otherwise I have to boil off a little more or less to get to my target gravity (I try to hit target gravity by varying volume if necessary, rather than vice versa). In practice, it's a much more inexact science, but it's nice to be able to get a ball park idea through the equations.

Tex Law's looks the least confusing. probably because he's using the software. I've noticed a lot more people on here mention ProMash than BeerSmith. Is it that much better? I definitely plan on using one or the other. I've played with the BeerSmith trial. Is there a ProMash Trial?

Mine's just a spreadsheet that I put together in two minutes because the numbers from BeerSmith were whack. It's really not very complicated. You start with a couple of known items - how much water you're adding to the grain, and how much you want to boil. The only other variables are how much water the grain absorbs, and how much you can't get out of the mash tun. I can email you a quick-and-dirty spreasheet if you would like.

IrregularPulse said:

Tex Law's looks the least confusing. probably because he's using the software. I've noticed a lot more people on here mention ProMash than BeerSmith. Is it that much better? I definitely plan on using one or the other. I've played with the BeerSmith trial. Is there a ProMash Trial?

Click to expand...

While I do use ProMash and look at the "water needed," I really do not need it. I have been brewing a lot longer than I have been using ProMash, but it takes only takes a little experience to figure out how much water you need for brewing once you see how your system works and how much water you leave behind. Just keep in mind that you will lose water that is retained in your mash, you will lose water to evaporation, and you will lose water to deadspace.

Deadspace and evaporation vary wildly from system to system and brewer to brewer, so you just have to find out where you are on that from your own experience. I lose about 1.5 gallons/hour to evaporation, but others lose much less and some lose more. Deadspace depends entirely on your system and your procedure, but it usually comes in at less than or around a gallon for most 5-10 gallon systems.

Your grainbed will hold onto about a pint of water per pound of grain in your mash, and you can pretty much count on that. If you add a total of five gallons of water to 10 pounds of grain for a mash, your runoff will come in right around 3.75 gallons. However, remember that you only account for that loss once. When you sparge, whatever volume you put in also should come at, as your grainbed already is saturated.

Using software or a spreadsheet is nice for figuring out how much water you need. However, after you get a few AG batches behind you, you will find that you use such a tool more to confirm your prediction rather than to make it.

As far as I know, there is no trial for ProMash. That has always irked me a bit, but I still like ProMash.


TL

IIRC, ProMash has a short trial. BeerTools Pro is the other, newer program to check out, and supposedly the latest version of that will include a trial.

You are correct, Bird. You can try out a limited version (i.e., only so many recipes and sessions, or something like that, and you don't get all the functions). Thanks for reminding me.


TL

I use this Excel Spread sheet called BatchSparge.xls and it has worked very well.

Thanks to everyone. Yesterday as I was reading I think it finally just "clicked" and I said to myself, "OH Yeah!", but that may change when I go to do my first AG session. I hate to think where'd I'd be without this forum. Probably in the basement clearing out all my brewing equipment for goodwill. Thanks again

Let me try an even simpler explanation if you batch sparge.

1. Figure out how much preboil volume you want to (or are capable of dealing with). For a 6 gallon finished batch, I start with 7.5.

2. Mash in with ABOUT 1.25qt/lb but don't obsess about it. Anything from 1 to 1.5 is fine.

3. Mash, vorlauf, drain the wort from the tun and MEASURE the volume. Now subtract this from the preboil volume you wanted. That number is how much you need to sparge with. I like to break this volume into two distinct infusions/drainings.

That sounds mighty familiar


TL

Reinforcement!

When I said it clicked earlier, That is exactly what popped into my head Bobby. Thanx for confirming my simple thinking. AG here I come!!! If I can ever find a friggin Keg to convert. What size Pot would be needed to boil 10 gallon batches? 12-13G?

15! Don't forget, to boil down to 10, you have to start at about 12. You can't boil 12 in a 13g pot; boilover city.

thanx all, Got all my peices and hope to assemble my MLT tonight

I'm also thinking of going AG, but I had another question along these lines:

When do you take a gravity reading? I would assume this would be pre-boil so you could see if you need to add any DME to reach your desired OG. Is this correct, or do you need to wait until you've boiled your wort?

Both- preboil and post boil. Actually, since I've been doing this for a while now, I don't take the preboil. My efficiency is not good (72-73%), but it is always in that range, so I know what to expect. But intially, a preboil reading (cool it down before reading- those adjusments are terribly inaccurate) is a good way to know if you're "in the ballpark" for your recipe. If you're just slightly off, you can just adjust your boil time some to boil off a little more. You can figure your efficiency going into the boiler, and then figure your brewhouse efficiency from the post boil SG.