How to Adjust for False Bottom

[PProtection]

Hey all. I just transitioned to using a 10 gallon pot with a false bottom for my mash tun. The false bottom has a good 1 1/2" to 2" space it leaves at the bottom of the pot. Do I have to adjust my beersmith or my recipe for the water that is going to just sit at the bottom without grain during the mash? I am not sure how this effects efficiency or how best to approach it. I assume this will effect efficiency but I am not sure if it's a "add more grain" or "add more water" fix.

e.g. If my 11lb grain bill is suppose to mash in 4.5 gallons of strike water, but it is really only sitting in 3.5 gallons of strike water (1 gallon below the false bottom without grain in it) do I add water or do I add more grain or do I do anything? For reference I am using a fly sparge.

I thought about just adding an extra gallon of water to my strike (so it sits at the bottom) but any tips from people who use a pot with a mash tun for a false bottom would be helpful. Also, any tips on how to adjust for this in beersmith would also be appreciated.

Thanks all!

 

[PantherCity]

"I thought about just adding an extra gallon of water to my strike (so it sits at the bottom) but any tips from people who use a pot with a mash tun for a false bottom would be helpful."

You're on the right track. Measure how much sits under your false bottom(N) and take that into account (add N# of gallons to your strike water). Because you are fly sparging I wouldn't worry about how it affects your efficiency.

 

[Bobby_M]

I don't understand why false bottoms would need to be up so high. Get it closer to the bottom of the pot and have the diptube go through it to suck the wort out.

 

[wildwest450]

There's a place in beer smith under your equipment called lauter tun dead space, just measure yours as suggested the plug it in, it's that easy.
A gallon seems like a lot to me.
_

 

[PProtection]

There's a place in beer smith under your equipment called lauter tun dead space, just measure yours as suggested the plug it in, it's that easy.
A gallon seems like a lot to me.
_

Thanks Wildwest450. I assumed that “lauter tun dead space” in beersmith is the amount of liquid left behind after the sparge, not the space beneath the false bottom during the mash (the amount of liquid left behind after a sparge is around ½ gallon whereas the space beneath the false bottom is around 1 gallon). I am not sure which measurement is correct to use.

I don't understand why false bottoms would need to be up so high. Get it closer to the bottom of the pot and have the diptube go through it to suck the wort out.

I agree Bobby, I ordered a polarware false bottom for my 10 gallon polarware pot and it came at that size. I could always try to cut it down more, but would rather just adjust my measurements than start cutting on the false bottom, but will do so if needed.

Does anyone else use the 10gal polarware kettle with the big false bottom?

 

[Bobby_M]

Area under a FB isn't technically considered dead space. I don't think anyone has defined this space so I've been calling it "slack space". If you have a dip tube under there, it will still drain it out. A full FB in a keg leaves 7/8ths of a gallon under it (like mine) but with a dip tube, I only leave 1/2 cup behind. Slack space is just a place where extra mash wort will collect and give the thick mash area the appearance and consistency of a um, thicker mash. 2 gallons is surely excessive, especially in smaller batches/beers where the total strike water would only be like 3 gallons.

Now I see that the polarware FB has welded on feet and that it would probably have to get REALLY close to the bottom to fit under the bulkhead.

I'd set up your ratio for 1 qt/lb and then add 2 gallons. Assuming a recirculation, enzymatically it acts as a slightly thinner mash but it will stir like a 1qt/lb mash.

 

[PProtection]

Thanks for the detail Bobby. I think the "slack space" is more in the range of 1 gallon (not 2 gallons) but I will measure it when I get home. For example, my last batch called for 4.5gal of strike but the grain portion was really only in 3 - 3.5 gal of water with the other gallon in the slack space. I guess I could add around an extra gallon to my recipes and see how it turns out and adjust accordingly. Eventually I will figure out what qt/lb ratio just works best with the slack space I have.

You also mentioned recirculation - do you mean with a pump system or a simple vorlauf? I do not currently have a pump system to recirculate, but I do vorlauf my wort after the mash (not sure how much of a vorlauf I should aim for though). Also, would a vorlauf during the mash help at all (to get the slack water into the grain) or is there to much risk of hot side aeration?

on a side note, I have noticed I can tip my kettle towards the valve and only leave behind around 1 cup to 1 quart. Without the tip it's closer to a half gallon.

Thanks for all your help! I am a relatively new AG brewer.

 

[Bobby_M]

The reason I recirculate is for heat adjustments. Any time you apply flame to it, you need to get that wort from the bottom to integrate back into the mash. It would be a chore to do it without a pump but I suppose you could collect runoff into a pitcher and pour it back in on the top. Without doing this, you could possibly boil the wort under the FB while the mash above is relatively unmoved. I don't think stirring is enough to equalize the temps.

Even if you don't direct fire, I'd drain off about a gallon and add it back on top at about 5 and 30 minutes into the mash to equalize temps.

 

[mmonacel]

See my post regarding the same exact question. For me, I have 1 gallon of slack space. I drain my tun entirely and then add 1 gallon of wort back in. That gallon will go right to the bottom and fill up the slack space (and hey - maybe even pick up more sugars on the way!). Since I'm not adding any additional water, my calcs aren't thrown off. I then do my sparging process and I know my grains are getting the full exposure to the water I intended. I've been hitting my numbers so it's been working for me.

 

[mmonacel]

I don't understand why false bottoms would need to be up so high. Get it closer to the bottom of the pot and have the diptube go through it to suck the wort out.

I agree with you on this. I would have preferred something along these lines however during my purchase I was told that since the bottom of my cooler was flat and not rounded like a keg, it would be difficult to create the void the diptube needs to operate well. Hence the reason for the stand. Might have been BS, but hey - it's working for me now. I could always modify it if needed I guess to be that way if it becomes a problem.

 

[Catt22]

IMO, it doesn't much matter when fly sparging. If done properly, there will be very little sugar remaining in any wort left behind in the "dead" space. IMO, so little that't it's not worth recovering. Not the same when batch sparging.