Review of OBK’s “grain defender” false bottom

During the craziness of the holiday shopping season, one of my favourite homebrew equipment and ingredient suppliers, Ontario Beer Kegs put their false bottoms on sale… I’d been eyeing up one for awhile and couldn’t resist ordering one even though it wasn’t officially designed to fit my mash tun. The tolerances are very tight here so there is a real risk in that if my mash tun was even slightly different in diameter from the mash tuns the false bottom was designed for, that either grain wouldn’t be effectively filtered, or the false bottom just wouldn’t fit. Thankfully, neither was the case and it fit perfectly. It’s sort of odd that so many stainless kettles have the exact measurements isn’t it? I’d guess they’re either all made in the same factory or with the same machine in China.



It fits perfectly!


Recirculation speed is king in tight mash temperature control in recirculating mash systems such as RIMS, HERMS, or my personal favourite C-HERMS. When there are issues with recirculation (which I’ve had my fair share of) it is very frustrating and can easily throw off the beer in terms of malt balance. My hopes were that with this false bottom I could eliminate all throttling of my recirculation speed, which I had previously put in place to prevent stuck mashes. I had also previously waited 10 minutes from my mash in to start recirculation for the same reason… well for my first brew with this false bottom I figured I’d test it hard by recirculating at full speed immediately after mashing in.




Unthrottled mash recirculation.


Well the false bottom passed it’s test. 60 minutes of full speed recirculation later, there was no noticeable decrease in performance. As a result I had some of the best mash temperature control I’ve ever had with my system. This was only for a single infusion mash, but I imagine this will be especially great for mashes with multiple temperature steps.



No signs of recirculation slowing down 60 minutes later.


I will say that the vorlauf was the longest I’ve ever required. It took about 5 minutes of recirculation for the mash to form a sufficient grain bed and filter itself completely. Small pieces of grain will make it through the false bottom without this.

I clean my brewery “in place”, which involves a couple rounds of cleaning solution recirculation. The first of these cleaning stages frees debris from my system. You can see in the absence of a grain bed, many small pieces of malt husk and endosperm made it through the false bottom. While this could be seen as a negative, with a recirculating mash system it’s not a problem, and I think in fact the coarseness of the false bottom is an advantage in these systems as it allows for high recirculation speeds. The trade off may be perfect for recirculating systems, but I expect brewers who do not recirculate would prefer either finer filtering or would want to combine this false bottom with a “bazooka screen” or secondary manifold.



It’s the grain bed’s job to filter these very fine pieces.


A couple other things you should know about if purchasing this product: it comes coated with quite a bit of machine grease. Clean it well. I suggest a couple rounds of warm TSP or PBW solution. Mine also came with a slight concave shape – I imagine due to how the steel is either manufactured or transported. This can be bent out flat easily. Lastly, the height of this false bottom creates over 2 gallons of space. This would not be accurately accounted for with a dead space measurement as this liquid is almost entirely recoverable with a dip tube. Instead, to obtain a grist to water ratio of approximately 1.25 lbs/qt above the false bottom, I enter a ratio of 1.75 lbs/qt in Beersmith. Doing this ensures that your strike temperature and mash chemistry calculations remain accurate. The height of this false bottom is another reason why it may only be suitable for recirculating mash systems. All in all I am quite happy with this purchase, and I feel it complements my system perfectly.



There is over two gallons of space below the false bottom, which can be difficult to account for in brewing software, and also may not be suitable for non-recirculating mash systems. My false bottom also arrived with a slight concave shape (shown here) which was easy to correct by hand.

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