Batch sparging water volumes, dead space, and false bottom w/ diptube

My MLT has a false bottom with a dip tube. The space below the FB is probably 1.5 gallons. With the dip tube, I can pick up all but 1/4 gallon. I double batch sparge.

When sparging I'm concerned that much of the water I add is mostly sucked up by the space below the screen and not really soaking the grains and extracting the remaining sugars. It's somewhat "wasted" water since it's contact with the grains is minimal as it passes through and settles on the bottom immediately. Unfortunately, this water is part of the runnings so when double batch sparging I have about 3 gallons never really in contact with the grainbed rinsing the good stuff.

I typically determine my total sparge volume by taking my target volume minus what first drained out of my tun. Should I be adding more to compensate for this dead space? In doing so I'll end up with more runnings than I'll need and those runnings will be somewhat diluted. Thoughts?

It sounds like you are draining most of the water out before you begin adding your sparge water is that correct?

I usually add the sparge water when the grainbed is barely suspended by the remaining water in the tun so that the grain bed is always suspended and not compacting as it flows.

One technique that I found to extract more sugars from the sparge has been to drain the wort until the top of the grainbed is at the same height as the remaining wort, then add the sparge water and let it sit for another 15 to 20 minutes before draining the remaining wort. If I get a smaller amount of wort than expected then I will typically add more sparge water and let it sit in the grainbed for 10 to 15 minutes to soak up the sugars in the grain and then drain it.

I think the key to the method above is that it gives the grain bed more contact time with the sparge water.

yes - fully draining and then sparging. Interesting process. I might give this a shot next time. At a minimum drain to where I estimate the FB is and then sparge from there. Thanks!

I love to fly sparge. I always get at least 75% efficiency as I am slowly running the water from the top of the grain bed down to the bottom and out the port while taking all of the sugars out with it until the running's are almost clear. This way you do not have to worry about the amount of sparge water you have as long as you have enough.

If I were to batch sparge I would fill it up, stir it, let it sit for 10 min, drain and repeat. The soaking is to make sure the bed settles for proper filtration and to eliminate channeling. Leaving the grains in the water will not yield more sugar as this is what the mash has done. I think that when you add water from the top, that water will carry a large amount of sugar with it to the bottom. Any water that comes after than will push the sugar loaded water out the port on the bottom of the kettle and carry the rest of the sugar with it. So really in the end what you have in the bottom of the kettle after your second sparging should have the least amount of sugar.

mmonacel said:

My MLT has a false bottom with a dip tube. The space below the FB is probably 1.5 gallons. With the dip tube, I can pick up all but 1/4 gallon. I double batch sparge.

When sparging I'm concerned that much of the water I add is mostly sucked up by the space below the screen and not really soaking the grains and extracting the remaining sugars. It's somewhat "wasted" water since it's contact with the grains is minimal as it passes through and settles on the bottom immediately. Unfortunately, this water is part of the runnings so when double batch sparging I have about 3 gallons never really in contact with the grainbed rinsing the good stuff.

I typically determine my total sparge volume by taking my target volume minus what first drained out of my tun. Should I be adding more to compensate for this dead space? In doing so I'll end up with more runnings than I'll need and those runnings will be somewhat diluted. Thoughts?

Click to expand...

First off, do you have a problem with low efficiency....I would think that if anything like you are describing is actually happening, you most definitely see an efficiency loss.

That being said, I'm not really following you...with batch sparging, how is location of the water (bottom vs. top) impact the amount of sugar dissolved in it?

In the typical batch sparge scenario (i.e. vorlauf and drain MT of first runnings--->add sparge water---> mix sparge water with grains---> vorlauf/drain ---->repeat with second round of sparge water) I don't see how that water is getting "sequestered" and not rinsing any of the grain.....are are mixing before draining, right?

broadbill said:

First off, do you have a problem with low efficiency....I would think that if anything like you are describing is actually happening, you most definitely see an efficiency loss.

Click to expand...

This is my second batch. First batch I had about 70 percent efficiency - not bad. This batch I had a thinner than originally planned mash (had to add water / ice to cool the initial mash) and so my sparge volumes were a bit less than I would normally do (but not by a lot) which resulted in a dryer looking bed. This got me thinking about where the water really is and a good portion was not re-soaking the grains. The efficiency loss seemed to confirm this.

broadbill said:

That being said, I'm not really following you...with batch sparging, how is location of the water (bottom vs. top) impact the amount of sugar dissolved in it?

Click to expand...

Water being dumped right onto the bed and straight down below the FB is (to me) presumably not putting as much additional sugars into solution than when the grains are being soaked again for another 10 min.

broadbill said:

In the typical batch sparge scenario (i.e. vorlauf and drain MT of first runnings--->add sparge water---> mix sparge water with grains---> vorlauf/drain ---->repeat with second round of sparge water) I don't see how that water is getting "sequestered" and not rinsing any of the grain.....are are mixing before draining, right?

Click to expand...

The process above is what I do. See second response for what I mean.

Why do you have so much volume under the false bottom?

If you think the spare under it doesn't play the same part in diffusion the sugar out, stir the grain really well, then drain two gallons and add back on top. Stir a bit again.

These types of rigs do better with fly sparging.

mmonacel said:

This is my second batch. First batch I had about 70 percent efficiency - not bad. This batch I had a thinner than originally planned mash (had to add water / ice to cool the initial mash) and so my sparge volumes were a bit less than I would normally do (but not by a lot) which resulted in a dryer looking bed. This got me thinking about where the water really is and a good portion was not re-soaking the grains. The efficiency loss seemed to confirm this.

Water being dumped right onto the bed and straight down below the FB is (to me) presumably not putting as much additional sugars into solution than when the grains are being soaked again for another 10 min.

The process above is what I do. See second response for what I mean.

Click to expand...

Here is my take FWIW....sparge water "location" in the MT doesn't make any difference whatsoever because you are mixing the grains with the sparge water during batch sparging. Sparging works to "rinse" the grains during because you are mixing a material with a high sugar concentration (grain)with a material of low/zero sugar concentration (sparge water). Once mixed, the sugar concentration equilibrates between these two materials. It is also consistent from top to bottom. Therefore sparge water under the dip tube, if properly mixed, has the same amount of sugar in it than the sparge water on top (or in) the grain bed.

Your lower efficiency in the second batch is most likely due to lower sparge water volume because your mash was thinner. The more sparge water you have, the better your efficiency.

Hope this helps.

Bobby_M said:

Why do you have so much volume under the false bottom?

Click to expand...

Looking closer it's almost exactly at 1 gallon. that's because my false bottom is set up with the screen directly above the ball valve / dip tube sitting on a stand of sorts.

broadbill said:

Your lower efficiency in the second batch is most likely due to lower sparge water volume because your mash was thinner. The more sparge water you have, the better your efficiency..

Click to expand...

Well, the total sparge volume was the same, just a thinner mash which resulted in less water being used for sparging (more water during mash in left less water for sparging to equal the pre-boil volume I wanted). [This may be what you meant.] My concern / theory was that b/c of my thinner mash this time and subsequently less sparge water used to equal my pre-boil volume, the grainbed was significantlly dryer (especially the top half) than it typically is during sparging because a lot of that sparge water was below the false bottom. Therefore the grains were rinsed less effectively.

Given that, I wonder if just adding a bunch more sparge water would rinse the grains better (more grains suspended in water). This would of course give me more runnings (more than I need), although I wonder if those runnings are more sugar-rich.

BTW - on this last batch I drained the tun and added back 1 gallon of the wort so it would settle to the bottom just below the FB which allowed me to make sure my sparge water was in full contact with the grain bed thoroughly rinsing it. On the second sparge I also brought the grainbed up to 170 successfully. I've now hit my highest mash efficiency at 72%. Before I was in low to mid 60's. There's probably some other things I can do, but I'm really happy with where I'm at right now.