Sanity Check - Profile for BrewZilla 65L w/Extensions

[Nagorg]

Hello,

I have a BrewZilla 65L with a boiler extension and the extended malt pipe. I'd like some input on what I "think" the equipment profile should look like.

First, I have downloaded the add-on profile for the 65L. The first thing I'm questioning about this is the numbers used for Mash Tun Volume and Recoverable Mash Deadspace. I'm not sure the numbers are truly correct based on what I've come up with for the extended version and this is causing me some confusion, hence the ask for a sanity check.
The volume of the standard malt pipe is less than the volume of the BrewZilla kettle. There is additional volume between the bottom of the malt pipe and around the sides (between the malt pipe and the kettle) where water cannot be in contact with the grain.

Moving on to my extended example...

The extended boiler volume is 23.72 gallons (28.125" tall x 15.75" diameter), That's the pure volume if it were full with nothing inside of it.

The extended malt pipe has a volume of 14.833 gallons (23.5" tall x 13.625" diameter). This is the only volume that has any chance of being in contact with the grain during the mash.

If you subtract the two, this should be the "Recoverable Mash Deadspace" at it's maximum. And that number is 8.887 gallons!

So, am I correct that I should use 23.72 gallons for Mash Tun Volume and set Recoverable Mash Deadspace at 8.89 gallons?

 

[Nagorg]

No input? I know it's Labor Day weekend. lol Seems like a legitimate question I have here. Just trying to make sense of these things that, frankly don't seem to add up.

Maybe nobody knows the answer...

 

[Nagorg]

FWIW, I'm not seeing any change in mash volumes when setting "Recoverable Mash Deadspace" to different volumes.

It appears to me that this setting does absolutely nothing. Is this a bug in the software? It's driving me crazy! lol

 

[BeerSmith]

Recoverable mash deadspace is used in some systems that have a significant volume below the mash screen but that volume can be recovered after the mash and put in the boiler. It will not significantly change your overall mash volumes as that deadspace is not lost, but it is used in the mash thickness calculations to get the water/grain right.

The tun deadspace is the volume that is not recoverable - i.e. it is actually lost when you do the transfer from the mash tun to the boiler. This will drive mash volumes directly as it is lost.

 

[Nagorg]

Okay, thanks for that. A couple more related questions then.

Recycling from my post:

The extended boiler volume is 23.72 gallons (28.125" tall x 15.75" diameter), That's the pure volume if it were full with nothing inside of it.

The extended malt pipe has a volume of 14.833 gallons (23.5" tall x 13.625" diameter). This is the only volume that has any chance of being in contact with the grain during the mash.

If you subtract the two, this should be the "Recoverable Mash Deadspace" at it's maximum. And that number is 8.887 gallons! This includes the volume beneath the malt pipe and around the sides.

So, am I correct that I should use 23.72 gallons for Mash Tun Volume and set Recoverable Mash Deadspace at 8.89 gallons?

@BeerSmith

 

[Nagorg]

Well, this topic has been driving me crazy. Crazy enough that I finally consulted with AI for my sanity check. Turns out that I've been on point with my assumptions, according to AI anyway. At least its feedback is the "Sanity Check" I've been looking for.

Sorry for being a "Meat Proxy", but it's relevant to my question posted here:
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Let me verify the actual BrewZilla Gen 4.1 dimensions to make sure I pair diameter and height correctly, since that materially affects the volume math.Good news — your numbers line up well with the published KegLand specs for the Gen 4 extended malt pipe (350mm dia × 600mm high ≈ 13.78" × 23.6", matching your 13.625" × 23.5" almost exactly), which confirms your dimension order is height × diameter for both vessels. That's important because it changes the volume math significantly, so I used that pairing throughout.

The physical picture​

RMD here isn't just the gap under the malt pipe — it's everywhere water can sit in the kettle but outside the malt pipe's grain-holding cylinder. That has two components:

1. Bottom gap — the malt pipe (23.5" tall) is shorter than the kettle (28.125" tall) and sits flush at the top, so there's a 4.625" tall slab of water below the pipe, spanning the full kettle diameter (15.75").
2. Annular sleeve — the malt pipe (13.625" dia) is narrower than the kettle (15.75" dia), so there's a ring of water surrounding the pipe for its entire 23.5" height.

Neither of these is in contact with the grain bed inside the pipe, but both stay in the kettle and get folded back in at boil — hence "recoverable."

The math​

Bottom gap:

• Kettle cross-sectional area: π × (15.75/2)² = π × 7.875² = 194.83 in²
• Height gap: 28.125" − 23.5" = 4.625"
• Volume: 194.83 × 4.625 = 901.1 in³ → 3.90 gal (14.77 L)

Annular sleeve:

• Malt pipe cross-sectional area: π × (13.625/2)² = π × 6.8125² = 145.80 in²
• Annulus area: 194.83 − 145.80 = 49.03 in²
• Height (malt pipe height): 23.5"
• Volume: 49.03 × 23.5 = 1152.1 in³ → 4.99 gal (18.88 L)

Total RMD:

Component	Gallons	Liters
Bottom gap	3.90	14.77
Annular sleeve	4.99	18.88
Total RMD	8.89 gal	33.66 L

This is identical to just computing (full kettle volume) − (full malt pipe volume) directly — I broke it into the two pieces mainly so you can see why it's a lot bigger than you might intuitively expect. The annular sleeve is actually the bigger contributor here, not the bottom gap, because even a modest 1.06" radius difference multiplied by 23.5" of height and the full circumference adds up fast.

Sanity check on magnitude​

• Full kettle volume (to the rim, with extension): 23.72 gal (89.8 L)
• Full malt pipe volume: 14.83 gal (56.15 L)
• Difference: 8.89 gal — consistent

That means roughly 37% of the kettle's total capacity sits outside the grain-contact zone in this configuration. That's a large fraction, but it matches what people report anecdotally about the extended malt pipe setup specifically — the homebrewtalk thread I found describing this exact BrewZilla 65L Gen 4.1 + boiler extension + extended malt pipe combo flags this as a bigger-than-expected deadspace, consistent with what the geometry predicts here.

Caveats before you lock this into BeerSmith​

• This treats both vessels as perfect cylinders. BrewZilla's Gen 4 base has a sloped/dished bottom for full drainage (per their marketing copy), not a flat bottom, so actual liquid volume in that bottom region will be somewhat less than the flat-cylinder math assumes — meaning your true RMD is probably slightly less than 8.89 gal, not more.
• Malt pipe wall thickness and the false-bottom screen height aren't accounted for; both are minor but nonzero.
• The gold-standard fix: do an empirical calibration. Fill the bare kettle (no malt pipe) to a known volume, mark the waterline, then insert the empty malt pipe and note how much the level rises — that rise tells you the malt pipe's displaced volume at that fill height directly, sidestepping any bottom-shape uncertainty. Do this once and you can true up the RMD value with actual data rather than idealized geometry.

For an initial BeerSmith equipment profile, I'd set RMD ≈ 8.7–8.9 gal (33–33.7 L), use it for your first calibration run, and correct it after that with the real measured value from that batch.