False Bottoms and bottom drains

[Fastline]

I have some questions on Bottom Drains and False bottom which i'm hoping some of the all grainer forum users could advise on my thermopot mash tun conversion

Is it best to have the drain in the centre of the pot or as close to one edge, I was thinking if in the centre it might create a more even flow through the grain bed maybe slighly better efficency, or if close to the edge pot could be angled slightly to to get more wort out?

Im going to make my own false bottom im thinking either 16swg or 18swg (1.5mm or 1.2mm) Stainless steel CNC punched out with a pattern of small slots 12mm x 1.5mm Is it best to have a small area below the false bottom or a larger void or does it really not matter how high I space it from the bottom, the holes are where i would put some M6 Button head screws to hold spacers on the bottom, probably put some more closer to the middle to support the weight of the grain too, but just an idea at the moment

I may go for a herms or rims set up in the future would there be any advantage in having a separate port in the bottom for that

[Fastline]

Can anyone advise if the gap under the fb is of any importance, would a small or bigger gap give any advantage or disadvantage

[Fil]

Err Dunno.. the collective wisdom/experience on the subject is a circa 1" void under a small scale Tun FB is sufficient as to distribute any suction from the drain and not require a front heavy (VOLUME) mash.. ie too high and the sparge volume may not be sufficient to rinse enough sugars and impact efficiency perhaps?

however options such as batch sparging and slower sparging could compensate?

but you might need to lookup and do the mathmatics to be sure..

My tun is drained from the side/front bottom, but i tend to batch sparge , i have no problems with my FB sat circa 15mm off the base so circa 12mm above the top of the skin fitting drain.

if you have the tools and ability to make your own fb why go for such an odd new design, why not emulate the blitchmann pattern which is respected and has great feedback.. you could make me one too while your at it

[Fastline]

Unfortunately the blitchmanm use quite a special punch to produce their pattern, I could get a tool made but would be expensive

I'm thinking this would produce similar results and be quick to produce, I may tighten the pattern up a little to get more holes in there

The reason i've gone for the the slots is i'm thinking it would be difficult for a grain to entirely block it, I've read of people getting good results using a dremel to cut slots, the CNC punch just does it much quicker and neater.

The Blitchmann also uses an alternating pattern i'm thinking this would create flows in a few different directions through the grain bed, so I thought i would try to achieve the same by alternating the pattern

[Fil]

fair enough..

fwiw the fb i used in my coldbox tun was probably something like 99% closed with 1mm holes spaced out in a bigger than 1" square grid pattern, it never stuck tho


So a simple 30%+ open perforated SS sheet FB should be fine for most brews imho..
A well doughed in mash shouldnt stick.

[Fastline]

I found some info on the web relating to the gap under the false bottom, Sounds like less gap is better when Single infusion mash with no re-circulation the initial flow washes enzymes away from contact with the grain bed stopping them converting the sugars and thus reduces efficiency.
Obviously not a problem if recirculating making more sense to me to go with a rims or herms
I may reduce the amount of slots as sounds like a slower flow through the the FB is better

[YeastWhisperer]

There should be no need to distribute suction because their should be none while continuous sparging. If suction is forming in one's mash tun while continuous sparging (a.k.a. fly sparging), then one is either running off too quickly or the mash bed is not draining fast enough. Suction does not matter with infusion rinsing (a.k.a. batch sparging) because the technique is not sensitive to downward flow through the grain bed.

OP, your design is the universally-accepted design that is used in most commercial brewery lauter tuns. You just need to ensure that you have between 15% and 20% open space. I use a 16% open space slotted false bottom in my mash tun that produces extraction rates of between 261 to 278 points per kilogram per liter (unweighted efficencies of 86% to 92%). I struggled to achieve extraction rates of more than 244 points per kilogram per liter with a perforated false bottom.


My Mash/Lauter Tun




With respect to distance between the floor and the false bottom, it depends on if the tun is going to be directly heat or not. One has to worry about scorching with a directly heated mash tun. If the false bottom is too close to the floor in a directly heated tun, it can create a superheated zone. This problem is more pronounced when one uses a shallow dead space false bottom in one's brew kettle, which is why Blichmann advises against using their false bottom in a boil kettle. I use perforated false bottoms and whole hops in my kettles, so that I can obtain bright cast-out wort. The false bottom rests on the curvature of the kettle at the bottom. I have to be careful about how much heat I apply to the bottom of the kettle or I get superheating under the false bottom.

[Fastline]

Hi Yeastwhisperer I was going to use a Bazooka Filter in my kettle that is going to be heated with 3Kw element or maybe two, do you find a perforated false bottom to be better here, I think i have some stainless perforated sheet but im sure its 3mm holes, would these be too big do you think or would i be better with the slotted design for the kettle too, the slots size is 1.5mm x 12mm