Last night I picked up a 10-gallon cooler mash tun. It was supposed to come with a 12" false bottom, but the LHBS was out of those. Instead they offered me a 10" false bottom, saying that it would work just as well but that my efficiency might be a little bit lower.

How would a smaller false bottom affect efficiency? I'm trying to picture how the smaller bottom would leave wort in the mash tun, but I'm not getting it.


The difference is so small, that I would NOT expect a change in efficiency. Efficiency with a bottom like that is more dependent upon how well your dip tube continues to pull wort off the bottom of the tun. If you are just using a tube connected to a bard on the false bottom then there should really be no noticeable change in efficiency with a false bottom that is only a couple inches smaller all the way around.

You don't even have a base line efficiency with that cooler yet, so the shop people are putting ideas in your head. Just start using it and see what you get.

  • Yep, it's a tube connected to an elbow pipe. I'll brew with it tomorrow and see what the efficiency is.
    – Hopwise
    Jun 2 '11 at 15:22
  • Keep in mind that your mash tun will have a very minor effect on your efficiency. Your grain crush is by far the largest variable, with water amounts and mash pH down the line after crush.
    – Denny Conn
    Jun 2 '11 at 17:38

If anything, I'd expect your efficiency to be a bit higher due to less dead space under the false bottom. In reality, I'd expect the difference to be virtually none.

  • Interesting idea. Probably to difficult to actually measure these changes accurately. Now if we were talking a 10 foot false bottom vs 12 foot in a huge commercial type tun... maybe we'd have something to talk about.
    – brewchez
    Jun 2 '11 at 16:43

Wouldn't the smaller false bottom allow for the outer edges of the grain bed to not be rinsed as well as a larger false bottom?

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