"Sinkhole" when batch sparging

Hey all, I'm having a problem when batch sparging, and hope to get a little advice from you batch sparge vets. Here's my setup:
Converted keg with 15 inch jaybird false bottom.
Standard ball valve/diptube pickup from dead center of screen.
I mash in, let sit for 20 minutes, stir.
20 minutes later, I start vourlof/recirc with pump very slow
When wort clears I've tried two methods: cranking the pump all the way (still recirculating) for 20 seconds, then transferring to BK. OR transferring to BK and running off at 1/2 throttle on pump. Both these methods give the same resulting problem, which is:
Big "sinkhole" forms about 4 inches in diameter where grainbed is a few inches below the rest. The wort channels to this spot, I can see it when wort level gets low enough. A little right and down from dead center (where the diptube would be).
After this first running, I add my second sparge water addition, stir, and repeat. I get the same dang hole in the same spot.
Has anyone had this happen? Jaybird sent me his level 1 screen, thinking that the FB might have been bowing and causing or contributing to the problem, but sadly, I used it yesterday and got the same result as before.
Finally, my efficiency isn't terrible considering it's channeling so badly. I'm getting between 67% and 74%, but I know I'm leaving sugars behind and want to get them!

could it be from your recirc line making direct contact with the same portion of the grain bed?? Interesting... and wierd. I've never had a channelling issue with my setup, which is very similar to yours (direct fired keggle with recirc, FB, and diptube).

I also sparge slow though. maybe about 1/4 turn of a ball valve. It takes me about 5-7 minutes to collect 2 gallons of runnings

Now that you mention it, I do have my recirc line above the spot where the hole forms...... For this brew I had a 2 qt/lb water to grain ratio, so with 23 lbs of grain the mash was nearly to the top of the keg. I would wonder if slowly vourlof/recirculating (about a gallon/minute) would actually penetrate straight down to the bottom forming the hole. I wouldn't think so, but definitely a possibility. Thanks for the thoughts.

I think channeling is generally only an efficiency issue when flysparging, as you are going to have liquid moving to that area, and not flowing through/dissolving sugars in other areas of the mash. If you're batch sparging and stirring before running off, you're dissolving the sugars into the liquid regardless.

+1 to a slow drain of the sparge. It should help prevent any channeling like you are having here.

one-L said:

I think channeling is generally only an efficiency issue when flysparging, as you are going to have liquid moving to that area, and not flowing through/dissolving sugars in other areas of the mash. If you're batch sparging and stirring before running off, you're dissolving the sugars into the liquid regardless.

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Right. Channeling isn't a factor at all for batch sparging so I wouldn't worry about it.

I assume your technique is to mash in, stir like crazy, and then recirculate later? Then, to draw off your first runnings, add the sparge water and stir like crazy, then draw off the second runnings? I assumed so, but your post wasn't clear and I wanted to make sure I understood your process.

one-L said:

I think channeling is generally only an efficiency issue when flysparging

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Exactly. When batch sparging you mix the hell out of everything before you drain, so channeling isn't a concern.

Yooper, yes I do it just as you describe. I always thought that you want the grainbed to drain uniformly whether batch or fly sparging. I'll try running off slower and dispersing the wort return on my pump line, to see if that eliminates the hole. Do you all crank the pump all the way to "set the grainbed" and then back down to whatever flow you like? Or do you recirculate until clear and then just run off at your preferred speed?

I recirculate and sparge at the same flow-rate, regardless of gristload, water ratios, or temperature...

Bdigs said:

Yooper, yes I do it just as you describe. I always thought that you want the grainbed to drain uniformly whether batch or fly sparging. I'll try running off slower and dispersing the wort return on my pump line, to see if that eliminates the hole. Do you all crank the pump all the way to "set the grainbed" and then back down to whatever flow you like? Or do you recirculate until clear and then just run off at your preferred speed?

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No, you don't need the grainbed to drain uniformly, and you don't want to drain slowly.

I'm simplifying the basics here, but when you batch sparge you're not getting sugars out of the grain from the process of diffusion, as you are in a fly (continous) sparge.

You stir in the "batch" of sparge water and stir like you mean it. Stir well and thoroughly, then immediately vorlauf and drain. You don't want the sugars to "settle" back on the grain- you want the sugars that were "knocked off" of the grain to be in the liquid and so you'll drain the liquid. The shape/size/consistency of the grainbed is immaterial and a slow drain may inhibit the sugars from being in solution rather than help your efficiency.

I know lots of batch spargers let the grain bed settle for 10 minutes, or drain slowly, and swear it works for them. I can't argue with success, but there is no scientific reason it would be better than a quick run off and no waiting period. Just the reverse would be more likely.

Yooper, you never mentioned how fast you run off, although I assume it's in the neighborhood of "fast." Does that mean full-bore? I understand the mechanics of draining the sugars with batch sparging, as opposed to rinsing them in fly sparging. So if my "sinkhole" is not a problem as you've said, I'm wondering how others claim to be getting much better efficiency using the same or similar techniques. I know that this is a well discussed topic, but when I get 67% using a fine crush, 2.0 qt/lb of grain in the mash, and sparge at 170 degrees, I wonder what the problem is.

Bdigs said:

Yooper, you never mentioned how fast you run off, although I assume it's in the neighborhood of "fast." Does that mean full-bore? I understand the mechanics of draining the sugars with batch sparging, as opposed to rinsing them in fly sparging. So if my "sinkhole" is not a problem as you've said, I'm wondering how others claim to be getting much better efficiency using the same or similar techniques. I know that this is a well discussed topic, but when I get 67% using a fine crush, 2.0 qt/lb of grain in the mash, and sparge at 170 degrees, I wonder what the problem is.

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Fast, as in fully open with the pump running full blast.

67% isn't a bad efficiency, but if you want to improve that you could try using 1.25-1.5 quarts of water per pound of grain, and increase the sparge water. It could be a pH issue- a pH of over 5.7ish can have less conversion.

I'd suggest seeing if the low efficiency is a mash issue or a brewhouse issue.

To check if it's a mash issue, check the SG after the mash. You should have near complete conversion. If not, then you know that's the problem. Then, to see if it's a lautering issue you could check the SG of the runnings. If the extraction efficiency is good, you could then look at brewhouse efficiency. That would entail seeing how much finished wort you're getting into the fermenter, as leaving a gallon of wort in the BK under a false bottom for example would lower the brewhouse efficiency. Also, double check your volumes to make sure that your volumes are correct.

Yooper said:

Right. Channeling isn't a factor at all for batch sparging so I wouldn't worry about it.

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Huh. You learn something every day! Thanks for clearing that up, I was draining my mash super slow for over a year now!

bknifefight said:

Huh. You learn something every day! Thanks for clearing that up, I was draining my mash super slow for over a year now!

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Take a look at www.dennybrew.com.

I do a single batch sparge with my system,I add all my sparge water, stir like hell, set my controller to 168 degrees and recirculate for 10 minutes.I drain at the same rate I recirculate and I get 80% efficiency.

Yooper - It's a mash issue, I'm checking the gravity and according to beersmith I'm never getting over %75 efficiency into the BK. Although, I'm eyeballing the volume, it's pretty close because I boil about 14 gallons in a converted sanke and there's only so much space left. Also, from what I've read on the subject, a thinner mash tends to improve efficiency.

Denny - thanks, I've seen your site and read it carefully many times. Also read a lot of your posts in other threads on similar issues.

Fat B - Are you getting 80% into the BK? You only stir once during the mash? I'm thinking I may need to stir more often and may not be converting fully.

Next brew I'm going to try doughing in at 140 degrees to eliminate any chance of dough balls, stirring 3-4 times over the course of an hour mash, and making sure my pump return line doesn't make a hole/indentation in my grainbed. Also from reading what Denny and others are doing, I'm going to calculate the ideal water/grain ratio that leaves me with near-equal runnings into the BK. For my system, that's 1.6 qt./lb which gives me about 7 gallons after running off the mash and 7 gallons from batch-sparging. After recirculating, I'll "let er rip" at full bore into the BK. That sound like a good plan? Thanks again everyone for the ideas.

Man, if you do all that, you're working too hard IMO! I mash in at mash temps, stir thoroughly then to eliminate doughballs and equilibrate the temp, then close the cooler and don't stir again til I add the sparge water. I get about 83-85% efficiency. If you're having efficiency issues, it's related to crush 90% of the time.

Ok, well maybe the repeated stirring won't help me. I am crushing pretty fine, and have experimented with conditioning with water and dry. I haven't seen much of a difference. On a side note, I have a barley crusher, and when I set it too fine, it won't crush at all. It doesn't pick up the grains to the rollers, or it will starting crushing, and then "miss" and spin without crushing. I'm getting pretty frustrated with it. I tried taking it apart and cleaning the rollers and ports that they fit in, but no help. I contacted the company for ideas, but no one got back to me.

I use a 52 quart cooler for the mash, stir the mash bed every 20 minutes, and collect first runnings at about half throttle.
To get 13 gallons into my BK I usually end up batch sparging twice (repeated checks of the third runnings have always ended up ~1.015). For each batch sparge I stir, let sit for 10 minutes, and collect at the same rate.
I get about 75% efficiency.
From what I am reading here, I don't need to stir the mash or let the sparge rest and I should collect runnings wide open?

northernlad said:

I use a 52 quart cooler for the mash, stir the mash bed every 20 minutes, and collect first runnings at about half throttle.
To get 13 gallons into my BK I usually end up batch sparging twice (repeated checks of the third runnings have always ended up ~1.015). For each batch sparge I stir, let sit for 10 minutes, and collect at the same rate.
I get about 75% efficiency.
From what I am reading here, I don't need to stir the mash or let the sparge rest and I should collect runnings wide open?

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yep, with a caveat on the last. I start my runoff pretty slowly while I vorlauf a qt. or so. Once the grain bed is set, I open it up full. It's not so much that you "should" as that you can go as fast as your system will allow. I have found no benefit to stirring as the mash is resting (all it did was make me lose heat) and after lots of experimentation I've found no benefit in letting sparge water sit before beginning the vorlauf.

Thanks for the reply Denny. I guess i thought it would be beneficial to stir at least some during the mash as i have seen many a commercial tun being stirred. I am happy to shave 20 minutes off my sparge time.

Denny said:

Take a look at www.dennybrew.com.

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We need to find a way to have every new all grain brewer read this page, very helpful, all questions answered, thanks again Denny.

I double batch sparge, and get between 78% and 85% efficiency depending on OG. On lower OG beers I often single batch sparge to save time, and still get well over 80% efficiency. As mentioned, channeling is a non-issue when batch sparging.

Bdigs said:

So if my "sinkhole" is not a problem as you've said, I'm wondering how others claim to be getting much better efficiency using the same or similar techniques. I know that this is a well discussed topic, but when I get 67% using a fine crush, 2.0 qt/lb of grain in the mash, and sparge at 170 degrees, I wonder what the problem is.

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Most likely the crush, or inaccurate measurements. Other possible causes are not breaking up the dough balls thoroughly enough at mash in, and not stirring well enough after adding each sparge addition. And 2 qts/lb is a bit thin for most grain bills, leaving you with very little sparge water. For batch sparging lauter efficiency is highest when the run-off volumes are close to equal. For most systems that works out to ~1.5 qts/lb for an average gravity beer, and a little thicker for higher gravity or thinner for lower gravity. And FWIW sparge temp has no effect on lauter efficiency when batch sparging.

Bdigs said:

Although, I'm eyeballing the volume, it's pretty close because I boil about 14 gallons in a converted sanke and there's only so much space left. Also, from what I've read on the subject, a thinner mash tends to improve efficiency.

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You might be surprised at how much a little volume reading error can screw up your efficiency calculations. If you want an accurate indication of your efficiency, then you might need to develop a more accurate method for measuring the volume. This explains how much small errors can throw the perceived efficiency off-
http://braukaiser.com/wiki/index.php?title=Troubleshooting_Brewhouse_Efficiency

Bdigs said:

Also, from what I've read on the subject, a thinner mash tends to improve efficiency.

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Conversion efficiency yes, but that's much different from lauter efficiency. As mentioned, equal volume run offs provide the highest lauter efficiency for batch sparging. The curve is relatively flat topped, so there is some wiggle room, but something at least close to equal should be the goal. This explains it pretty well, and also compares lauter efficiency in single batch sparging to multiple batch sparging-
http://braukaiser.com/wiki/index.php?title=Batch_Sparging_Analysis

Bdigs said:

Also from reading what Denny and others are doing, I'm going to calculate the ideal water/grain ratio that leaves me with near-equal runnings into the BK. For my system, that's 1.6 qt./lb which gives me about 7 gallons after running off the mash and 7 gallons from batch-sparging.

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That sounds much better, but using 1.6 qts/lb won't always get you equal 7 gal run off volumes. You'll need to mash a little thinner for smaller grain bills, and a little thicker for larger grain bills to maintain those ~7 gal run off volumes. The math is really easy once you know the grain absorption for your system though. If your grain absorption is 0.125 gal/lb (that's what mine is), then you'd multiply the size of the grain bill by 0.125, and then add 7 gal, then add your MLT deadspace, and that's how much water you need to dough in with. If your initial run off ends up being slightly more or less than 7 gal, simply adjust the sparge volume accordingly.

Denny said:

Man, if you do all that, you're working too hard IMO! I mash in at mash temps, stir thoroughly then to eliminate doughballs and equilibrate the temp, then close the cooler and don't stir again til I add the sparge water. I get about 83-85% efficiency. If you're having efficiency issues, it's related to crush 90% of the time.

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This.

northernlad said:

Thanks for the reply Denny. I guess i thought it would be beneficial to stir at least some during the mash as i have seen many a commercial tun being stirred. I am happy to shave 20 minutes off my sparge time.

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Yeah, but AFAIK you're not brewing on a commercial system. Not everything commercial brewers do translates to homebrewing. And AFAIAC, that's one of the great things about homebrewing.

Juan, thanks for the detailed reply. I brewed a Robust Smoked Porter yesterday, carefully measured my volume, and finally got my mill working right. As Denny said earlier, it's probably the crush, and I think that was a decent part of it (low efficiency). I cranked my mill as tight as it could possibly go, and "conditioned" my malt with a spray bottle of water. Man, it was such a beautiful crush.... I thought about taking a picture of it but didn't. The husks were mostly totally intact, with nice white flour from the endosperm (or whatever it is). Bottom line, very nice super-fine crush with big fat husks to help in filtering. After running off the mash (at 145 degrees) and doing one nearly-equal volume batch sparge, I hit my preboil volume of 14.5 gallons dead on. Beersmith tells me I got 89% mash efficiency, which I am VERY content with. All said and done I only got 76% brewhouse, which I thought was odd, since I only left about 3/4 gallon behind in the BK, but I'm still happy with that. Finally, for the main reason I started this thread, my "sinkhole" was caused (as someone suggested right away) by my pump-return line. Got that fixed, so I am dialed in now! Thanks for the help everyone.

Bdigs said:

Juan, thanks for the detailed reply. I brewed a Robust Smoked Porter yesterday, carefully measured my volume, and finally got my mill working right. As Denny said earlier, it's probably the crush, and I think that was a decent part of it (low efficiency). I cranked my mill as tight as it could possibly go, and "conditioned" my malt with a spray bottle of water. Man, it was such a beautiful crush.... I thought about taking a picture of it but didn't. The husks were mostly totally intact, with nice white flour from the endosperm (or whatever it is). Bottom line, very nice super-fine crush with big fat husks to help in filtering. After running off the mash (at 145 degrees) and doing one nearly-equal volume batch sparge, I hit my preboil volume of 14.5 gallons dead on. Beersmith tells me I got 89% mash efficiency, which I am VERY content with. All said and done I only got 76% brewhouse, which I thought was odd, since I only left about 3/4 gallon behind in the BK, but I'm still happy with that. Finally, for the main reason I started this thread, my "sinkhole" was caused (as someone suggested right away) by my pump-return line. Got that fixed, so I am dialed in now! Thanks for the help everyone.

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3/4 gallon left behind is a lot. That's fine, of course- but if you add that 3/4 back in and calculate, your brewhouse is probably like 78-80%.

I have my system set up to 75% brewhouse efficiency, and it's perfect for me. No stuck sparges, and a dependable efficiency for each and every batch. It's not the number that is important (unless it's very low), it's the consistency so you can plan your recipe and grain bill and hopping based on a consistent number. It sounds like you got it all fixed up.

3/4 is a lot? Did I mention I'm doing 11 gallon batches and this recipe had a lot of hops? Seems like a normal amount to leave in the BK to me. As far as brewhouse efficiency, are you supposed to add the volume you leave behind in the equation? I thought brewhouse efficiency was the volume that actually makes it into the fermenter...

Bdigs said:

3/4 is a lot? Did I mention I'm doing 11 gallon batches and this recipe had a lot of hops? Seems like a normal amount to leave in the BK to me. As far as brewhouse efficiency, are you supposed to add the volume you leave behind in the equation? I thought brewhouse efficiency was the volume that actually makes it into the fermenter...

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.75 of a gallon of a 11 gallon batch is nearly 7%. That is, 7% of your wort left in the BK.

That may not be alot to you, and that's fine. But leaving 7% of the wort behind would mean that you're reducing your brewhouse efficiency by 7%. That's of course ok, but that would explain why your brewhouse efficiency takes a large hit.

What do you do to get that last 7%? Are you transferring everything from your BK into the fermenter? There's a lot of trub, hops, etc in there that I don't want to go into my fermenter. How are you filtering that out?

Bdigs said:

What do you do to get that last 7%? Are you transferring everything from your BK into the fermenter? There's a lot of trub, hops, etc in there that I don't want to go into my fermenter. How are you filtering that out?

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I have a CFC, so the cold break goes into the fermenter. For hops, I either use a bazooka tube (for whole leaf hops) or bag them. For pellet hops, they usually just fall down to the bottom of the boil kettle when I recirculate before I go through to the chiller. I end up with some trub, too, but it's not that much.

And the 7% doesn't matter, if you choose to discard it! I was just mentioning why the brewhouse efficiency is lower than expected.

Or you can adjust your recipe to make 7% more wort.

Right, I'm definitely not concerned about the 3/4 gallon left behind, it's completely saturated with pellet hops and trub, so I don't want it anyway. A friend of mine pours everything through a fine mesh bag, but I don't want to chance introducing bacteria with that method. I always assumed everyone just left that portion behind? As soon as my wort starts getting cloudy when draining the BK, I usually cut it off. I'd much rather have a cleaner ferment than a few more pints to drink.

Bdigs said:

Right, I'm definitely not concerned about the 3/4 gallon left behind, it's completely saturated with pellet hops and trub, so I don't want it anyway. A friend of mine pours everything through a fine mesh bag, but I don't want to chance introducing bacteria with that method. I always assumed everyone just left that portion behind? As soon as my wort starts getting cloudy when draining the BK, I usually cut it off. I'd much rather have a cleaner ferment than a few more pints to drink.

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That fine.

My system is different, and all the hops debris settles down with the trub in the end anyway so I don't worry about that in the wort. Most of my wort goes into the fermenter. I leave very little behind, but I recirculate so what I leave behind is usually hotbreak and some hops debris. I have very clear wort before it goes through the chiller, and of course the cold break goes into the fermenter.

It's really just up to the individual brewer.

I understand your concerns with filtering through a mesh bag or other, but with a proper soak in the sanitizer of your choice, its really not an issue. I filter my wort through a chinois which removes all of the hops and the rest of the wort and trub, save for about a cup, goes in the fermenter. Nothing wrong with that that all. In fact, I ran out of whirlfloc some time ago and I haven't seen any loss of clarity.

I let pretty much everything but whole hops (which go into a bag) go into the fermenter.