False bottom tun - strike water volumes?

[timw]

Morning all...

I've upgraded my old coolbox/copper tube manifold mash tun to a thermo-pot with a false bottom and had a couple of questions.

The drain is in the base of the thermopot, not the sidewall. The false bottom is a circle of stainless steel mesh, with some bolts that create little legs to elevate it off the bottom.

This creates around 1" or 3cm of void beneath it, above the base of the pot and drain.

Question 1: Is there an ideal depth to that void? The overall diameter of thermopot must be around 45cm so the grain bed is spread to a thinner depth over a wider area than in my old small rectangular coolbox so not sure how this will change the mash efficiency... time will tell.

Question 2: As it stands, that void creates quite a bit of dead space beneath the mesh, and therefore beneath the grain bed.

With my coolbox mashtun, when calculating my volume of strike water I had no dead space (aside from the negligible volume taken up by the copper tube manifold). I would just calculate my mash volumes on the general ratio of 1.5lts per kilo of grain (give or take).

With this false-bottom tun, I havent measured that dead space beneath the bottom, but it must a good few litres of water beneath it, meaning when I come to mash in, that liquid isn't "available" and I guess would lead to a very stiff mash above the false bottom.

Therefore - do I just work out that volume and increase my mash liquid volume accordingly?

 

[timw]

Having measured that dead space beneath the false bottom, it is 2lts of volume.

When calculating my mash strike volumes - if the grain/water ratio to my given recipe requires say 14litres - do I put in 14 as, or do I need to add an extra 2lts on for that deadspace under the bottom - bumping it up to 16litres?

 

[Dads_Ale]

Pretty sure that is what I used to do when I was using my mash tun with a false bottom, otherwise ,as you say, the mash would be stiffer than expected. I don't think I actually measured the dead space but rather just added the water until it reached the false bottom and then added the correct strike volume.
One thing you may find with a bottom drain is that you do get some bits come out which would have sat on the bottom of the tun with a side drain, this does depend on how fine your filter is and how tight a fit it is.

 

[grahameys]

You need to add that 2L onto your strike volume so in your example 16litres is correct. If you use brewing software, you can setup your equipment profile with the 2L dead space and it will calculate for you accordingly.