False Bottom not working effectively

[darrylsnow]

Hi all,

I've upgraded from a 20L homebrew system to a 200L system and used it for the first time the other day. I previously did boil-in-the-bag but for my new system I have a false bottom. For my first test I decided to try a half-batch. The problem was that several kilos of grain managed to get down beneath the false bottom, blocking the outlet and also clogging the pump with grain, preventing me from being about to recirculate or transfer to the boil kettle.

I've been thinking about what could have gone wrong and the possible solutions:
- maybe I need a full batch so that there's enough grain weight to compact the grain bed above the false bottom so that the grain at the bottom doesn't fall through the holes or the small gaps around the side
- maybe I turned on the pump before the grain had chance to settle which created a vacuum and sucked the grain down through the false bottom
- maybe I knocked the false bottom when doughing in

I'm thinking of putting a roll of muslin cloth around the edge of the false bottom to get a better seal against the edge of the tun. Maybe also put a layer of muslin cloth over the false bottom itself to provide an extra layer of filtering. Another idea is to put a steel scourer (like for scouring dishes) in the tun outlet to filter out more grain - I'm worried though that it will still clog up the outlet and restrict flow to the point that my self-priming magnetic-drive pump won't work or might cavitate...

Any suggestions or ideas would be greatly appreciated. Thanks!

 

[The Brew Mentor]

A picture or 2 would be helpful.
Brian

 

[darrylsnow]

Here are pics of the tun and the false bottom. As you can see, the holes are the right size, too small for that kind of grain to fall through. There is a roughly 4-5mm gap all the way around the edge of the false bottom.

 

[GernBlanston]

The holes in the false bottom look fine to me. you will get some grain bits through before the bed settles, but not that much and not grain of any size. My money would be on the gap around the edge. There needs to be a tight seal or the fluid will go the path of least resistance, and with a gap that size, all sorts can go through. Also the small batch vs large batch theory has some possibility's, as does the bumping or floating of the bottom during dough in, however these would be minimal. Once the bottom settles down it should do its job. Id start with the perimeter seal.

Is there any way to lower the false bottom on those stout tanks? That is a massive dead space you got under there. My bottom is a domed version that sits on the bottom of the tun with a centered pickup tube, and has very little wasted dead space. If your false bottom could set down flat on the bottom of the tun you would get a better seal on the edge, and have the weight of the grain/wort holding to tight.

 

[Nosybear]

As high as that puppy sits, I'm pretty sure it's the gap around the edges. Start there, then check your crush. It looks to me as if some of the hulls were shredded, indicating you may be over-milling the grain. 4mm is large enough to let grain through. With my false-bottom I sometimes get a lot of grain under it and in my wort. I can trace that to the crush - I use the mills at the local homebrew store and switching from one to another gives me different results.

So there may be two problems going here. Start with one - the gap around the edges - and if that doesn't work, go to the other.

 

[The Brew Mentor]

4-5 mm around the perimeter seems to be a large enough gap to allow the crushed grain through especially if the false bottom wasn't perfectly centered. So if the false bottom shifts while mashing in or any stirring, you could end up with a 8-10mm opening!

The 1st thing I'd do is contact the manufacture and demand a better fitting bottom.
If that isn't possible, I'd have SS spacers welded on the false bottom to keep it centered.

After that, I'd make sure to damper your pump on the outflow side to almost closed when first staring your re-circulation. Allow the grain bed to set before increasing the flow.

Depending on your process, you may want to increase your strike water amount to account for the dead space under the bottom. I'd likely do this.

I do have a thought on making a seal for the perimeter but I'd only do that as a last ditch effort because an add on seal that isn't stainless and rigid will likely just become a problem.

Hope this helps,
Brian

 

[darrylsnow]

Thanks, yeah I've sewn some muslin cloth around the edge of the false bottom so hopefully should get a tight seal... and hopefully it won't soak up too much wort :?

The false bottom stands 65mm from the bottom of the tun, which is just above the outlet, so that means about 16L of deadspace... I can tilt the tun to get most of that though and can take it into account when calculating mash water. I'm doing continuous sparing (or hoping too once I can be sure there's going to be no grain clogging up my pump) so will just make sure I get enough wort for the boil. Brings efficiency down though I guess but.. well see for now.

 

[The Brew Mentor]

Have fun cleaning that! :?
You can put a turn down elbow on the inside of the tun and as long as the flow is consistent, it'll suck right down to the bottom when transferring out.

I do batch sparging on my system and re-circulate while changing temperature and or clearing wort before pumping to my BK. After the MLT is drained, I'll let it rest for 30 minutes or so and then drain it again before emptying it. This always gives me over 1 gallon of additional wort that I add to my boil or boil separately and keep for making starters.

I'd seriously call the manufacture about the poor fitting bottom.

Brian