I just did my 4th brew, my OG was lower than expected, and I'm looking for help with process improvements. I'm doing an all grain process. I have an 8gal kettle, a 2gal kettle, and a 0.5gal kettle. For the mash tun I have a 10gal home depot converted cooler with ball valve control spigot.

My process is as such:

  1. Day before - fill the kettles with water, let them sit 24 hours with a Campden tablet shared between the pots.

  2. Heat 6.5gal of water in the 8-gal kettle to 160F. Warm the mash tun, check the water is still 160F.

  3. Dump the grain into the mash tun,
  4. Tip the 6.5gal of 160F water into the mash tun. Actually this starts out by moving it 1 quart at a time as I'm unable to safely dump the entire 6.5 gal of hot water in one shot anyway, and I heard it was better to add it slowly to the dry grain.
  5. Stir with my giant 24" spoon to check no air pockets (just at the start)
  6. Then leave for an hour. (temp remains constant for the hour within 150-155F - typically around 152F)
  7. Recirculate until the flow of wort is relatively clear
  8. Drain until empty back into the 8 gallon kettle - this typically yields about 4.2 gal.

  9. Meanwhile I've heated the 2 gal kettle and 1/2 gal kettle to 170F

  10. Dump 2.5gal of 170F water into the mash tun to sparge
  11. Stir briefly
  12. Wait 15 minutes
  13. Recirculate until flow of wort is relatively clear
  14. Add this to the kettle until the kettle is back up to the 6.5gal mark

  15. Boil for an hour adding hops and Irish moss as prescribed

  16. 45 minutes into the boil add the wort chiller to sanitize it (no water flow connected).
  17. Transfer to the sink, connect the water flow to the chiller, also add blocks of ice into the sink
  18. Stir the wort with the chiller and drop the temperature down to 70-75F
  19. Siphon to 6.5 gal better bottle
  20. Test OG - this is usually done with the final, rather trubby, bit of the wort.
  21. Pitch yeast
  22. Wait until airlock starts to bubble, then chill to prescribed fermentation temp in a temp controlled modified-freezer.

My recipe involved 11 lbs of grain for a pilsner, with an expected OG of 1.049 mine measured 1.044, so a little lower than expected. My previous brew called for an expected OG of 1.062 but my process only yielded 1.051 so lower still.

I'm wondering - are my OG's lower because I'm using a higher volume (6.5gal for the boil) than a typical recipe expects?

Specifically, with a 5gal recipe - what exactly is supposed to be 5gal? The pre boil volume, the post boil including trub volume, the volume initially put into the fermenter without the trub, or the bottled volume? I've been trying to target 5gals into the bottles, my last round yielded 4.66gal. But perhaps this is my misunderstanding and might completely explain my OG delta?

MANY thanks for reading this long one!


3 Answers 3


Change that batch sparge to a fly sparge if you can. Use a good false bottom with little dead space (something like this works great: http://morebeer.com/products/stainless-steel-false-bottom-12-diameter.html). Also remember that the sparge needs even, unidirectional flow to get the sugars away from the grain. Never stir it if you don't absolutely have to. By stirring you're pushing sugarless, slightly tannic water from the top of the grain bed closer to the drain, making the wort weaker and more bitter.

  • Well, one easy switch in process would be rather than fully draining until empty, and then adding another 2.5gal of water. I could drain it until the water level is just below the grain level and then add a quart at a time, while continuing the sparge. However, this would mean that the sparge water isn't spending as much time on the grain - would this be better?
    – Roland
    Dec 13, 2014 at 3:27
  • I have a bazooka strainer attached to the inside of the mash tun (in lieu of a false bottom).
    – Roland
    Dec 13, 2014 at 3:28
  • I find that the speed of the sparge doesn't make a huge difference for me, but I think mine takes 30 at a minimum.
    – Pepi
    Dec 13, 2014 at 3:38
  • And it looks like bazooka filters come in different sizes... Since the sparge flow is driven by gravity, and takes advantage of the higher density of sweet wort, it helps to access to as much of the bottom of the grain bed as possible. OTOH if the filter is short you could tilt the pot toward the outlet during the sparge, that should eliminate 'dead spots' at bottom.
    – Pepi
    Dec 13, 2014 at 3:43
  • My bazooka filter is about 12 inches long, it spans the entire width of the bottom of the cooler. Your comment of 30 minutes to sparge is interesting, that's MUCH longer than I'm taking, perhaps that's something to change. I would say I'm draining the first 4 gallons in 10 minutes, then doing a batch sparge, waiting 15 minutes and then draining that in about 5 minutes. I have a very nice controllable ball valve on the mash tun so I could easily slow the flow rate down and then do a fly sparge that took significantly longer. I'll try that. Thanks for the advice.
    – Roland
    Dec 13, 2014 at 15:46

I, too, was always coming up a few points short on my OG. My epiphany was an article in BYO magazine (I think) that explained the need to adjust recipes for one's own equipment and efficiency. My experience lead me to believe that recipes generally use a 72-75% efficiency value, which could explain why those are the defaults in brewing software.

I scaled my recipes using a 68% efficiency and now I almost always hit my target OG, without any equipment changes! It just costs me a little more base malt, but that's all.

I'll enter a recipe into brew software like Beersmith, Brew Toad or Brew Target (free). I'll set the efficiency at 75% and then add all of the ingredients in the recipe. I'll adjust the efficiency slightly until it matches the recipe's OG (usually 72-75%). This represents the "originally published" recipe.

Next, I'll change the efficiency to 68% (for my equipment) and adjust the malts (usually only the base) until I match the original OG of the recipe. Most software has an option to automatically scale the ingredients when you make efficiency or volume changes.

Published recipes make assumptions and should only be used as a base. Every brewer would need to make tweaks to account for his/her own process, equipment, efficiency, etc. I'm a novice brewer that switched to all-grain after my first batch. My first two all-grains were disaster-ish: drinkable but very disappointing. So now I just throw a little more grain into it. A pro brewer with crazy efficiency would probably use less grain than what most recipes state.


First, when a recipe says 5 gallons that generally refers to post-boil volume into the fermenter. This is how kits do it and I think public recipes in like BYO or zymurgy follow the convention.

That said, I'm curious about your numbers. Could you give more detail about the recipe you were brewing for those example volumes? Is this for the mentioned 11 pounds of grain, because if it is you're using far too much mash water.

Pardon me if this is a different recipe and you know this already...Your target should be 1.3-1.5 quarts of water per pound of grain. Numbers vary a lot online, but you should expect grain to absorb ~.5 quarts per pound of grain. If your mash is too runny it won't convert as well as you want it to, which might be responsible for your low gravity. If it seems like your grain isn't absorbing as much as it should, you might still have some dough balls in your mash that aren't getting wet. I add grain to my water so that I can stir constantly with something slotted, seems to get me less dough issues.

But double check that math, also it might be helpful to check your post-boil volume as well as your pre-boil, I don't see that in your writeup. Also marking your kettle and measuring your boil-off per hour would be useful in tweaking your pre-boil target volume to make sure you get as much wort out as you want.

  • I'm heating about 9gals total water that goes into the mash tun, 6.5 to start and 2.5 to sparge. However, I'm only taking 6.5 out into the boil kettle. I'm perhaps putting 0.5gal too much as there's about that much left after I get the first 6.5gal out. However the 11 lbs of grain seems to be absorbing 2 gallons. Which is considerably higher than your estimate.
    – Roland
    Dec 20, 2014 at 6:25
  • Then I boil the 6.5gal, frankly I think my boil isn't particularly vigorous as there's nearly as much left at the end of the boil. Then I'm putting all of that, excluding the trub into the fermenter
    – Roland
    Dec 20, 2014 at 6:40

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