[Robert]

An alternative to knifing the top dough (that's English for Oberteig) is to just take your spoon and gently stir up the top inch or so of the grain bed into the liquid.   It will settle with the protein sludge more dispersed through the material instead of as a solid cap.

[mabrungard]

As Rob just pointed out, cutting the top dough, oberteig, or schmutzedecke is not the way to go. It violates every principal of flow through granular media to just "cut" the layer. What good is cutting a thin groove in the layer going to do in comparison to dispersing and trapping that doughy material within the upper portion of the grain bed?

A manometer is only needed below the false bottom or at the bottom of the tun. Two manometers are not needed. The most important thing that I've found in the almost 20 years of brewing with a manometer-equipped tun, is to NOT allow too much drawdown to EVER be applied to the grainbed. In my experience, you don't want to draw down the head level at the bottom of the bed any lower that the bottom of the bed. When using a pump, you can impose a suction on the bottom of the bed that is several feet below the bottom of the bed. That is way too much suction and that will compact the bed. Monitoring and limiting the drawdown is the best way to avoid compacting the bed.

Regarding the "grain pulling away from the walls", what sort of false bottom is in that tun? It sounds like the center of the false bottom is collapsing. 

[tommymorris]

Why does my wife’s manometer read zero around me?

[mabrungard]

Why does my wife’s manometer read zero around me?

Ha! I didn't even think of that.

[Joe T]

As Rob just pointed out, cutting the top dough, oberteig, or schmutzedecke is not the way to go. It violates every principal of flow through granular media to just "cut" the layer. What good is cutting a thin groove in the layer going to do in comparison to dispersing and trapping that doughy material within the upper portion of the grain bed?

A manometer is only needed below the false bottom or at the bottom of the tun. Two manometers are not needed. The most important thing that I've found in the almost 20 years of brewing with a manometer-equipped tun, is to NOT allow too much drawdown to EVER be applied to the grainbed. In my experience, you don't want to draw down the head level at the bottom of the bed any lower that the bottom of the bed. When using a pump, you can impose a suction on the bottom of the bed that is several feet below the bottom of the bed. That is way too much suction and that will compact the bed. Monitoring and limiting the drawdown is the best way to avoid compacting the bed.

Regarding the "grain pulling away from the walls", what sort of false bottom is in that tun? It sounds like the center of the false bottom is collapsing.

It's a flat, slotted false bottom that sits on a 5 x 3 tic tac toe type of grid. It's extremely sturdy. I could easily stand on it when it's installed in the tun. Sorry, I can't seem to attach a link or picture.
So if I install a single manometer below the false bottom, what will it look like during optimal flow vs. excessive flow?

[ynotbrusum]

I experienced compaction on recirc (Herms) so I simply crushed a bit coarser and run off a bit slower, until the problem was solved.  My system works with a mill gap of .030” and the outlet valve on the pump at half way open initially, then after the first mash step (Hochkurz), I run wide open.  I can run it half open for the whole mash, but my ramp times suffer, especially getting to mash out.

[BrewBama]

I experienced compaction on recirc (Herms) so I simply crushed a bit coarser and run off a bit slower, until the problem was solved.  My system works with a mill gap of .030” and the outlet valve on the pump at half way open initially, then after the first mash step (Hochkurz), I run wide open.  I can run it half open for the whole mash, but my ramp times suffer, especially getting to mash out.

That’s interesting. I mill at what would probably be considered course grits (I don’t have sieves to measure) and recirculate throughout a Hochkurz mash (RIMS). But if at any point during the mash or lauter I set the pump output valve wide open the suction will compact the grain bed, flow will stop and I’ll cavitate the pump. 

In lieu of a manometer, over several brews through some educated guesswork, I found a sweet spot for my system which includes a grist mill, water to grist ratio (1.75 qts/lb) and setting for the MLT pump output linear flow valve.  I measured the valve gap and now set the pump to it each time I brew. These combined constants allow good flow across the element but not so strong as to compact the grain bed. 

There were several points of frustration (one ‘interesting’ 8 hr brew day comes to mind) until I came to this particular combination. The frustration made me dig in to the available information to determine why I was having trouble. Basically, I had to understand my system. I decided I can’t control variability of agricultural products but what I can control I will.  My results lately have been pleasurably consistent.

Edit: the pump output valve is set at 5/16” which I measured at .7 gpm.

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[Joe T]

I experienced compaction on recirc (Herms) so I simply crushed a bit coarser and run off a bit slower, until the problem was solved.  My system works with a mill gap of .030” and the outlet valve on the pump at half way open initially, then after the first mash step (Hochkurz), I run wide open.  I can run it half open for the whole mash, but my ramp times suffer, especially getting to mash out.

That’s interesting. I mill at what would probably be considered course grits (I don’t have sieves to measure) and recirculate throughout a Hochkurz mash (RIMS). But if at any point during the mash or lauter I set the pump output valve wide open the suction will compact the grain bed, flow will stop and I’ll cavitate the pump. 

In lieu of a manometer, over several brews through some educated guesswork, I found a sweet spot for my system which includes a grist mill, water to grist ratio (1.75 qts/lb) and setting for the MLT pump output linear flow valve.  I measured the valve gap and now set the pump to it each time I brew. These combined constants allow good flow across the element but not so strong as to compact the grain bed. 

There were several points of frustration (one ‘interesting’ 8 hr brew day comes to mind) until I came to this particular combination. The frustration made me dig in to the available information to determine why I was having trouble. Basically, I had to understand my system. I decided I can’t control variability of agricultural products but what I can control I will.  My results lately have been pleasurably consistent.


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I definitely can't run wide open. I control my mash pump output with a ball valve. Maybe I need to look at a linear flow valve for better control.
Doing a full volume mash, I'm at almost 3 quarts per pound.

[goose]

Also, if the grain bed is compacting and somewhat collapsing towards the center so that the wort is going around the grain bed instead of through it, then my efficiency takes a big hit, which is frustrating to me.

Not to further the debate about the utility of a long vorlauf, but a long vorlauf is the culprit behind the teig--and therefore it's ultimately behind the grain compaction and low efficiency you're experiencing. You're taking the very fine particles that get through the false bottom and depositing them on top of the bed, where they accumulate. Longer vorlauf = more accumulation. So cutting the teig becomes more important with a long vorlauf.

Do you also do protein rests? They cause a ton of teig. But we'll save protein rests for another thread ;-)

For cutting the teig, I would just dip in a long spoon until you feel a little resistance, then go a tiny bit deeper and start gently raking. No visual necessary. But a coarser crush alone might fully solve your problem.

I always knife my grain bed during runoff, I use the flat handle of my stainless steel spoon.  I learned that during my pro gig at Hoppin' Frog.  It does seem to improve lautering efficiency.  I usually go about 2 inches into the grain bed (for a 10 gallon mash) and 1 inch for a 5 gallon mash and I always have an inch or two of liquid on top of the grain bed.  You will feel the resistance when you get into the grain bed as has already been posted.

[mabrungard]

So if I install a single manometer below the false bottom, what will it look like during optimal flow vs. excessive flow?

Well I'm sure you recognize that with no pumping, the level in the manometer will be coincident with the level in the tun. What I've found to be a 'safe' pumping flow rate is when the level in the manometer is pulled down almost to the level where your manometer plumbs into the tun. If the manometer level gets much lower, you'll pull air into the mash...and that's not good.

Now it might be safe to pump harder than what I've described, but that would require that you set up your manometer with a U-tube section than descends lower than the bottom of the tun. Since I don't want to deal with having something like that on my tun, I live with drawing down my 'straight' manometer level about to the bottom of the tun.

Another thing that many brewers don't know, is that the permeability (ability to pass flow) of the mash bed changes during the course of the mashing period. It can be quite low initially and it does rise. A manometer enables the brewer to properly throttle the flow to the permeability that the mash bed is currently delivering. You'll just keep adjusting the wort valve through the mash with the aim of keeping the manometer level near the bottom of the tun.

[majorvices]

Why does my wife’s manometer read zero around me?

Bwahahahaha!

[majorvices]

A manometer is only needed below the false bottom or at the bottom of the tun. Two manometers are not needed.

It helps to have to have two though because you can see if you are pulling too fast with two. If the one above the false bottom starts to fall you can adjust your pump speed or valve flow and if you bring them close to alignment you know you aren't running too fast. That said though you can fix a lot with adjusting your grind. When I have had the grain pull away from the sides it has usually been when the grain has been ground too fine.

I'll add: This is certainly a "first world" home brewing problem from a guy who "grew up" Zap papping and Denny Conn batch sparging. 

[Joe T]

Thank you everyone. This discussion has been very informative and helpful for me to take the next step down the rabbit hole in refining my process. 

[mabrungard]

It helps to have to have two though because you can see if you are pulling too fast with two. If the one above the false bottom starts to fall you can adjust your pump speed or valve flow and if you bring them close to alignment you know you aren't running too fast.

Keith, you still only need one. The head drop observed under the false bottom still signals that you're pulling too much. A manometer that is higher in the tun doesn't provide you additional information. For the granular media that is the grist, the headloss is proportional to the depth through the bed. If you're blinding your false bottom, then you long ago exceeded the flow rate that you should have operated at.

[majorvices]

I see what you are saying Martin and maybe on a system where you can see the top easily you are correct. But if you can't easily or accurately judge your water level (say a closed system or a system that you have to access the top via cat walk) two helps.