Why are my batches so small?

I'm relatively new to all grain, and I'm having this problem where I'm expecting a post-boil amount of somewhere around 5.25 gallons of wort , but I end up with around 3.5 -- tops. What am I doing wrong?

The wort I do end up with is always within a few degrees of OG of what the recipe tells me to expect, and my mash efficiency is always around 80-85%. I'm writing this because a couple weeks ago this happened and, like a fool, I topped it off to what I was expecting; predictably, I ended up with a stout you could see clear through!

What can I do to squeeze out those extra 14 bottles?

That is a huge difference. Are you using electric? Electric for some reason boils off more water. Are you sure that you have the proper amount of preboil wort (i.e. 6.25-7 gallons)? Are you boiling longer than 60-90 minutes?

What are your preboil volumes. How much are you boiling at the start? Volume of strike water? Volume of sparge water?

For my see-thru stout, I mashed 10.75 lbs. of grains in 3 gallons, and I sparged with 3.25. Boil time was 90 minutes (my burners are two gas jets on top of my kitchen stove). I tested my burners / pot this morning, and I found it boiled off .75 gallons of water in 60 minutes.

I don't measure my pre-boil wort; I just drain the mash tun until I can't possibly get any more out. Do you think I need to use more sparge water?

Should I always collect about 6.5 to 7 gallons of wort if I wish to ferment 5.25 gallons? If so, wouldn't that screw up my OG?

According to beer smith, you should be mashing in with about 3.36 gallons and sparging with about 4.6 gallons. Doing the ol' 1.5qt per Lb. of grain math, says to mash in with 4 gallons and sparge with about 4 as well.

How were you coming up with the water volumes? You have to account for the grains sucking up a pretty good amount of water during the mash and sparge.

Well for 10.75 lbs of grain you will lose about 1 1/4 gallons due to grain absorbtion. Then figure whatever losses due to mash tun design... mine is 1/2 gallon. Yes, you should measure what you are getting out of mash so you know what to sparge with (here you will usually get out what you put in).

EDIT: And if you are losing approximately .75 per hour to evaporation, after 90 minutes you would have lost about 1 gallon... so at the very least you should have 6.25 gallons total pre-boil.

Albondigo said:

For my see-thru stout, I mashed 10.75 lbs. of grains in 3 gallons, and I sparged with 3.25. Boil time was 90 minutes (my burners are two gas jets on top of my kitchen stove). I tested my burners / pot this morning, and I found it boiled off .75 gallons of water in 60 minutes.

I don't measure my pre-boil wort; I just drain the mash tun until I can't possibly get any more out. Do you think I need to use more sparge water?

Should I always collect about 6.5 to 7 gallons of wort if I wish to ferment 5.25 gallons? If so, wouldn't that screw up my OG?

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I would really suggest investing in something like Beersmith to help you out with the water volumes. I'm finding that for a 5.5 gallon post-boil volume so I get a little over 5 gallons of relatively clean wort into the fermenter I am at close to 8 gallons pre-boil if I am looking at a 90 minute boil.

Bottom line is that you need a lot more volume of water if you want to end up with 5 gallons of beer. It's not the end of the world if you have to top up your fermenter a bit, but I really would suggest some software to help out.

I'd say that your sparge volume is definitely too low. If I make a generic recipe in Beersmith with 10 lbs of base grain, 75% efficiency, single infusion medium body mash, 11% boil-off per hour, 5.25 target volume, here is what the mash schedule looks like:

12.50 qt strike water
Round 1 batch: 1.56 gallons @ 168F
Round 2 batch: 3.48 gallons @ 168F

Your infusion is close to 1.25 qt per lb (about the same as BS), your sparge is 1.79 gallons less than what BS calls for.

How did you calculate your efficiency? It seems like if you had that high efficiency, regardless of amount of boil-off, topping off back to 5.25 would result in a reasonable OG.

Also, the important boil-off parameter is %/hour. When you measured 0.75 gallons, how much did you start with?

Albondigo said:

If so, wouldn't that screw up my OG?

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No, your OG is what is expected post boil. Now if you are getting close to the OG and you only have 3.5 gallons of a 5 gallon batch, that tells me your efficiency is way low. As you boil the gravity increases because as the water is being boiled off, the remaining wort is more concentrated.

+1 to getting Beersmith or similar program. I should mention that my numbers are based on my mash tun with dead space of 0.25 gallons.

Are you sure your efficiency is that high? If you are expecting 1.07 with 6.5g of wort but you are getting 1.07 and only 4g, then your efficiency is not accurate. I agree with what the others are saying as well though that you should be using more water.

This thread will help you: https://www.homebrewtalk.com/f36/how-much-water-does-grain-absorb-42932/

You need to use the right amount of strike water, calculate how much water you will lose to grain absorption, and then calculate the right amount of sparge water. Plan on your efficiency going down with the extra water.

Thanks for all the amazing tips, everybody.

The general consensus seems to be that I'm not using enough sparge water. Most of the recipes I've done recently have come from this book... which is funny, because I just read its reviews on Amazon, and several of them criticize the amount of water it recommends for mashing and sparging.

I'll definitely use more water next time.

It all comes down to tuning your system. It took me a few tries but I came up with water amounts that work well for the brews I do in my system. I mash in with 3.5 gallons of water, and do 2 batch sparges of 3 gallons. This gives me near 8 gallons pre-boil. Boil for an hour, let how-trub settle out, and I get between 5.5 and 5 gallons of wort. Play around a little, and measure the liquid coming out. I marked a piece of CPVC with a line per gallon in my brew pot. This helped alot.