Or mash tun aspect ratio, if you like. Tall and skinny, or short and wide? I know a deeper grain bed (tall and skinny) will be better for lautering purposes, but will a flatter grain bed (short and wide) be better in any way? I've read mixed reviews online, but thought I'd solicit some opinions here.

I'm batch sparging now, but will likely move to fly sparging in the future.

  • I'm curious why you think you'll move to fly sparging.
    – Denny Conn
    Jan 25, 2012 at 22:09
  • @DennyConn Mostly to try something different to see how it fits in with my system and brewday.
    – JoeFish
    Jan 25, 2012 at 23:37

2 Answers 2


John Palmer says

Deeper grainbeds have more uniform rinsing, all else being equal.

An more uniform rinsing can mean increased yield, so then shape does have some impact. As Denny says, taller is better since there is more chance for the water to rinse the grains when fly sparging. (But, up to a point, if the grain bed is very deep then it might become compacted, which leads to stuck sparge or increased channeling further down the grain bed.)

Previously, I used a 70qt cooler for 5 and 10 gallon batches, batch sparged, and typically got 65% extraction, and usually 70% for 10 gallon batches. I'm now using a blichmann 20 gallon kettle and false bottom, and got 90%-92% on each of 10 brews so far.

I don't think the change in efficiency is entirely due to the shape, but I always felt the cooler was far too large for the batch size, making it difficult to get an even temperature. As well as the different MLT shape, the improvement in extraction is probably also due to these other changes in brewing process:

  • using a pump to recirculate the mash (more even temperature and enzyme distribution)
  • using a precisely engineered false bottom - my cooler had a hand made manifold of CPVC pipe...not quite precision engineering! (reduced channeling)
  • close monitoring and adjustment of the pH level of the mash (increased enzyme activity)
  • mashing out - more efficient lautering

I'm not adding fly sparging to this list because I really don't know if that improves efficiency - I've not done a batch sparge to directly compare. Will batch sparge the next brew and I'll update this answer with the result.

  • Thanks for a thorough answer. How do you like the 20 gallon kettle for 10 gallons batches? Too much headspace? Not enough for stirring? I'm always slopping mash outside of my cooler while stirring, because half the time it's full to meniscus levels.
    – JoeFish
    Jan 26, 2012 at 14:23
  • You're welcome. The 20 gallon kettle is fine for 10 gallon batches. For regular strength beers, mash is usually at the 8 gallon mark, so it's possibly overkill, but for big beers, or pushing 15 gallons the extra space is needed. I wen't 20/20/20 for BK/MLT/HLT and have not regretted it. The blichmann false bottom does a good job. See theelectricbrewery.com for details.
    – mdma
    Jan 26, 2012 at 15:41
  • Oh hey, that's you? I'm Nostalgia from HBT. I've been eyeballing your rig for quite some time ;) I'm all-electric too, with 25 gallon boil and HLT kettles. But I only bought 2 kettles when I started (dummy!) and now need to upgrade my little 50qt cooler. I'm doing bottom drains and a homemade false bottom.
    – JoeFish
    Jan 26, 2012 at 15:59
  • 1
    The problem with John's statement is that it totally overlooks batch sparging, where you drain, not rinse. His answer is valid for fly sparging, but not at all for batch sparging.
    – Denny Conn
    Jan 26, 2012 at 19:46
  • @joe, I'm not "Electric Kal", as we call him, just someone that followed his build with some customizations.
    – mdma
    Jan 26, 2012 at 23:17

For batch sparging, it doesn't matter. For fly sparging, taller is a bit better.

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