Underletting w/ a false bottom question

[mongoose33]

I finally have my RIMS system up and plan to do a run this weekend. I have a false bottom drawing off into the ball valve, into the pump, into the RIMS and then back to a distribution manifold on top of the mash.

But...I've been underletting, and wondering how people do that. Do you just pour the grist in on the false bottom, knowing some's going through, and it'll eventually filter out?

I do have a BIAB bag I probably could line the kettle with before pouring in the grist.

I've never used a false bottom before, so unclear how this will work with doing underletting.

 

[Gnomebrewer]

I underlet with a false bottom. I accept that some smaller stuff will come through and filter out.

 

[day_trippr]

I have the Blichmann FB. Dust might get through it but that's pretty much it. I used to subscribe to the "foundation water" practice but realized I didn't need that extra step, so now I just dump the grist into the dry mlt and start the underletting...

Cheers!

 

[schematix]

Crushed malt goes in the top. Water goes in through the bottom. Gets a good stir then i recirculate.

Blichmann FB never lets me down with barley grist but anything flaked plugs it in an instant. YMMV.

 

[Murphys_Law]

I just started underletting with a false bottom and a bag. I don’t recirculate though. Seems to work just fine.

@mongoose33, are you doing full volume mash? I’m doing full volume / no sparge and am struggling a little with water volumes in the boil kettle since I’m not hanging (dripping) my bag. Grain absorption is high and I feel like I’m leaving a lot of “wort goodness” in the mash tun.

 

[mongoose33]

I just started underletting with a false bottom and a bag. I don’t recirculate though. Seems to work just fine.

@mongoose33, are you doing full volume mash? I’m doing full volume / no sparge and am struggling a little with water volumes in the boil kettle since I’m not hanging (dripping) my bag. Grain absorption is high and I feel like I’m leaving a lot of “wort goodness” in the mash tun.

Yeah, full-volume mash, no sparge. Not unlike BIAB, though I leave more wort behind in the mash tun this way.

I'm trying to implement as much of the LODO approach as I can. Before my recirc setup, I was simply doing full volume in a cooler mash tun, which sat up above the boil kettle on a couple milk crates. I could thus drain/rack that wort right into the kettle.

The recirc system I'm hoping will do a couple things. One is to control the mash temp better. Another is to reduce the need to stir, which can contribute to O2 entering the mash. I'm also hoping it might contribute to greater efficiency, which would somewhat offset what you note above--leaving behind "wort goodness" in the mash tun.

I brewed yesterday for the first time using this approach. Success? Yeah, partially. Didn't quite get the efficiency I was hoping for, but there are a lot of moving parts here and I don't have a complete handle on them yet.

As far as the mash, I have a sight glass to monitor the wort coming out of the mash tun. Early on, particles, but those went away and I had clear wort. I did do a sort of partial stir a couple times; not completely confident I am not getting some kind of channeling, but then again, I have no prior experience with this.

A few pics showing what I'm doing; not sure the return manifold is in the right position; it's an inch or two under the surface of the mash, which I take as good as it allows me to use a mash cap.

 

[FunkedOut]

I do the exact same; grist on the dry false bottom and underlet the strike water.

Using the Ss Brewtech InfuSsion Mash Tun and false bottom, I was very disappointed at the amount of stuff that gets through.
I started BIAB and went to a separate mash tun to get clearer wort by filtering through the grain bed rather than pulling the bad and watching all the flour get through the bag.
Huge disappointment the first couple brews with the size and amount of stuff that needed to get recirculated to the get filtered.
The biggest downside is that when the mash runs dry, all the extra filtering created by the recirculation is wasted, as the last bit of water brings with it all sorts of solids.

You can add more water to the mix to keep the grain bed wet to avoid this.
I chose a different path.
I got my hands on some 304 stainless #80 mesh, which has holes ~240 microns big (BIAB material is ~210 microns). I "sewed" it to my false bottom with some stainless safety wire.
With this set up, I get a worst case kettle clarity of BIAB.
I still add a little extra sparge water to keep the cloudiness away from the kettle at the end of sparging.

 

[Murphys_Law]

@mongoose33 - would you mind sharing your eff. target and actual? Any thoughts on where you missed the #’s?

My current set up is similar to your previous one. I use a round 10g cooler but move the wort back and forth with a small pump instead of gravity. I have a false bottom and bag in my cooler and underlet.

I moved in this direction to try and incorporate some LODO practices into my brew day.

I’d be curious to hear your experience or thoughts on bag vs no bag and a false bottom. I’m always looking for small changes which produce better results!

 

[mongoose33]

I couldn't tell you my target--I'm always targeting a specific OG, not a specific efficiency. A couple years ago I was hitting 80 percent, but with this new system I'm not sure.

The issue is in part the no-sparge. I'm trying to account for losses in the system--deadspace in the fermenter, losses in the hoses, pump, and CF chiller, trub losses at the end--and mostly at this point I was trying to get a good beer, which I think I have done.

I cut back the grain bill by a pound from a previous batch--that undoubtedly accounted for a few gravity points. Part of this was being uncertain whether I could get all that grain *and* the water in the mash tun. Another pound of grain would have been fine.

I ended up with just about 6.5 gallons in the BK, and started with 8.25 gallons of strike water. Grain Bill was just shy of 14# (10# Maris Otter, 3# Rye Malt, 8 oz Choc Wheat, 4 oz flaked Rye).

I didn't boil off as much as usual, which also was worth a few points in the OG. I need to go and do a little calculation and see what those changes would have wrought. Normally a 6.5-gallon batch would boil off to 5.5 gallons, but I only had maybe a 1/2-gallon boiloff.

My major motivation was to get the system to work, now I'll tweak it a bit. I'd never used a false-bottom before, and was interested in seeing how that worked. I did a couple of minor stirs, I suspect if I'd shut off the pump and stirred it might have helped. I have no idea if I had any channeling. I ran the pump pretty slowly, trying not to compact the grain bed.

 

[day_trippr]

fwiw, it was noted by the LoDO folks that there actually is a compelling need to give the mash a stir (gently!) after the underlet process is complete. I found the same truth in practice, otherwise there's a decent delta-T from bottom to top of the mash that takes significant time to even out from recirculation...

Cheers!

 

[ba-brewer]

On the topic of temperature, are people doing anything to preheat the mash tun before adding the grain and underletting or do you just up the temp of the strike water to compensate for the heat loss?

Also how fast or what kind of flow do people use when underletting.

 

[Murphys_Law]

On the topic of temperature, are people doing anything to preheat the mash tun before adding the grain and underletting or do you just up the temp of the strike water to compensate for the heat loss?

Also how fast or what kind of flow do people use when underletting.

For my last batch I heated about 1g or so of water on the stove and put that in my cooler for about 20 mins, dumped the water, milled directly into the cooler, and then began the underletting.

I think I lost any benefit of preheating with the time it took to mill, etc. I came out a little low on my target mash temp.

I use one of those cheap, small brown pumps and I just let it go wide open. The pump isn’t that powerful so I don’t feel I’m having any issue with flow rate.

And I usually start to give a gentle stir once I have enough water to do so. I’ll stir one more time when the water is fully transferred. I desperately want to stir about every 15 or 20 mins and am trying to break that habit.

 

[day_trippr]

I use BeerSmith with my well-tuned equipment model, an IR temperature gun to take the MLT temperature, and a 24" stemmed digital thermometer to get the temperature at the middle of a crushed grain bucket, and let it calculate the strike water temperature. I rarely miss my mash temperature by more than a few tenths °F, it's one of the things BS is good at

Cheers!

 

[FunkedOut]

That sounds great!
I found the BS calculations for strike temp to be perfect when not accounting for equipment temp.
If I try to model my insulated mash tun, it’s not right.
For now, I preheat the mash tun, uncheck the box and all is right.

 

[mongoose33]

On the topic of temperature, are people doing anything to preheat the mash tun before adding the grain and underletting or do you just up the temp of the strike water to compensate for the heat loss?

Also how fast or what kind of flow do people use when underletting.

When I used a cooler mash tun, typically I would pour 1 gallon of boiling water into it to preheat it.

On my maiden voyage Saturday I just had the cold mash tun kettle. Didn't occur to me to preheat it, in retrospect I probably should have done that. I was counting on the RIMS to maintain temps, but there was a couple degree drop or more in the BK. I need to add some reflectix insulation to the BK to help account for that. I'll also probably use some 1" foamboard insulation to set it on.

As far as flow, I'm at around 3/4 gallon per minute.

 

[ba-brewer]

thanks everyone.

I went from a cooler to a RIMS setup about a year ago and have not had to really worry about mash in temp. I suppose with a RIMS or HERMS might be best/OK to be a bit on the low side vs too hot.

 

[jcav]

If you have grains falling through your false bottom and you want to mitigate this, I would recommend this little bad boy:

https://www.norcalbrewingsolutions.com/store/Level-3_15-Inch_FB_Stand.html

I use this under my false bottom and it surrounds the dip tube and I can mash high percentages of wheat and starchy adjuncts and this thing just flat out works. I do mash in a keg though and it fits under my false bottom perfectly. Also boosts the stability of the false bottom as it is very robust and holds the weight of the grain very well. I do not know if it will work for your system but I never get a stuck mash with this. I do use a pound of rice hulls with it too. Something to think about, it has made my brew days very smooth and I recirculate the mash at full bore with no restrictions on my pump. Good luck!

John

 

[MSK_Chess]

I finally have my RIMS system up and plan to do a run this weekend. I have a false bottom drawing off into the ball valve, into the pump, into the RIMS and then back to a distribution manifold on top of the mash.

But...I've been underletting, and wondering how people do that. Do you just pour the grist in on the false bottom, knowing some's going through, and it'll eventually filter out?

I do have a BIAB bag I probably could line the kettle with before pouring in the grist.

I've never used a false bottom before, so unclear how this will work with doing underletting.

I fill just above the false bottom then add grain. It seems to prevent any from falling through.

 

[day_trippr]

Right, that's the old-school "foundation water" technique. I used that with my 10g Rubbermaid with a perforated FB because that style is far less resistant to clogging up or passing grain chunks than the stamped Blichmann FB, and it seemed to help avoid issues...

Cheers!

 

[MSK_Chess]

Right, that's the old-school "foundation water" technique. I used that with my 10g Rubbermaid with a perforated FB because that style is far less resistant to clogging up or passing grain chunks than the stamped Blichmann FB, and it seemed to help avoid issues...

Cheers!

Lol old school, awesome, i had no idea that such a technique had a name, I was forced by the slings and arrows of outrageous fortune to do something after suffering too much dust during one batch.

 

[MSK_Chess]

I like the little inline sight glass, that's pretty cool.