Guide
False Bottoms Explained
The component that decides whether your runnings flow. Domed beats flat for two separate reasons.
The short answer
A false bottom is a perforated plate that sits above the vessel's base, holding back the grain while wort drains through. A domed plate beats a flat one because the dome resists collapse under grain weight and traps less wort beneath it -- flat plates both bow and leave more dead space.
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What it does
Separates wort from grain
After the mash, you have a vessel full of hot sweet wort and spent grain, and you need the wort without the grain. A false bottom is a perforated plate that sits a small distance above the vessel’s base with the outlet beneath it. Grain stays above, wort drains through the perforations and out.
Crucially, the plate is not the whole filter. Perforations of 1 to 2 mm would let plenty of grain through on their own. What actually filters is the grain bed itself -- the husks settle into a matrix that catches fine particulate, and the plate just supports it. That is why husk integrity matters and why your crush gap and your drainage behavior are connected.
Domed or flat
Two separate reasons the dome wins
Plate geometry compared
| Domed | Flat | |
|---|---|---|
| Resists collapse under grain weight | Yes -- arch geometry | Bows in the middle |
| Dead space beneath | Less -- follows the vessel base | More -- parallel gap |
| Wort left behind | Less | More |
| Even drainage | Good | Good if it has not bowed |
| Price | Slightly higher | Lower |
An orange rule marks the better of the two on that row.
Reason one: it does not collapse
Fifteen pounds of grain plus the water it holds is a substantial load on a thin perforated plate. A flat plate bows in the middle under it, and a bowed plate sits closer to the base in the center than at the edges, which produces uneven drainage and channeling. A dome is an arch, and an arch carries load.
Reason two: less dead space
Dead space is the wort sitting beneath the plate that you cannot drain, and it is wort you paid for in grain. A flat plate held parallel above a flat base leaves a uniform gap of that volume. A dome follows the vessel’s base contour more closely and leaves less. On a 5 gallon batch the difference is modest; across a year it adds up.
Sizing
Match the internal diameter closely
This is the specification to get right. A false bottom that is too small for the vessel lets grain pour round the edge and under the plate, which defeats the entire purpose -- you end up with grain in the outlet and a blocked valve.
- Measure the vessel’s internal diameter, not its nominal capacity. Kettles of the same stated volume vary in dimensions.
- A snug fit is what you want. Slightly undersized with a silicone gasket or a tight shoulder is better than a visible gap.
- Check the connection to the outlet. Some plates have a central fitting; others rely on a silicone tube to the vessel’s pickup. Both work, and the tube version needs the tube to be the right length.
Alternatives
Braid and manifold
A false bottom is the best answer and not the only one.
- Stainless braid. A length of braided stainless hose sleeve attached to the outlet. Very cheap, surprisingly effective in a cooler, and the standard budget solution. Its weaknesses are that a heavy grain bed can crush it flat and it is harder to clean properly.
- Slotted copper manifold. Copper pipe with saw cuts along the underside, arranged in a loop or grid on the vessel floor. Traditional, a satisfying weekend project, and it distributes the draw across the bed better than a single pickup does -- which matters for fly sparging.
- Bazooka screen. A tube of fine mesh screwed onto the outlet. Compact, cheap, and prone to clogging with fine particulate because the filtration area is small.
- A grain bag. Brew-in-a-bag dispenses with the whole question: the bag holds the grain and you lift it out. No false bottom, no manifold, no dead space.
Troubleshooting
When drainage goes wrong
Common drainage problems
| Symptom | Likely cause | Action |
|---|---|---|
| Grain in the outlet | Plate undersized or lifted | Check fit; secure the plate |
| Flow stops entirely | Compacted bed | Stir, drain slower, add rice hulls next time |
| Flow fast then stops | Channeling -- bed collapsed unevenly | Slow the drain rate; check for a bowed plate |
| Lots of wort left behind | Dead space | Domed plate, or a lower pickup |
| Cloudy runnings | Fines passing through | Recirculate the first runnings to set the bed |
The most common real cause of a stuck drain is not the hardware. It is a crush that shredded the husk -- usually from running a mill at drill speed -- so the bed has no filter matrix and compacts into a plug. Slow your mill before you blame your false bottom: how to mill grain.
Terminology context: mash tun vs lauter tun.
What we recommend
The products on this page
The standard answer
Entry tier
Stainless Domed False Bottom
Various
A domed perforated 304 stainless plate with 1 to 2 mm holes. The dome resists collapse under grain weight and traps less wort beneath it than a flat plate.
Spec sheet
- Material
- Perforated 304 stainless
- Perforation
- Typically 1-2 mm holes
- Shape
- Domed -- resists collapse under grain weight
- Sizing
- Must match the vessel's internal diameter
- Connection
- Silicone tube to the pickup, or a center fitting
- Dead space
- Domed designs trap less wort than flat plates
What it is not good at
Must match the vessel's internal diameter closely -- grain escaping round the edge defeats the purpose.
Who it is for
Any vessel where you drain wort off a grain bed
The vessel it goes in
Mid tier
Insulated Mash Tun with False Bottom
Igloo conversion / Spike
An insulated 10 gallon cooler with a false bottom holds mash temperature for an hour and lets you drain cleanly. Cheapest route into all-grain.
Spec sheet
- Capacity
- 10 gal (fits a 5-6 gal batch comfortably)
- Insulation
- Holds mash temp within 1-2 F over 60 min
- Manifold
- Domed false bottom, braid or slotted manifold
- Valve
- Ball valve bulkhead through the wall
- Heat
- No direct heat -- infusion steps only
- Best for
- Batch sparging without an electric system
What it is not good at
No direct heat, so steps mean infusion arithmetic.
Who it is for
Batch sparging without an electric system
Where it is built in
Mid tier
Anvil Foundry 10.5 Gallon
Anvil Brewing Equipment
The grain basket's dual-height false bottom is the lautering element, factory-matched to the vessel. No sizing to get wrong.
Spec sheet
- Capacity
- 10.5 gal / 40 L
- Power
- Switchable 120V 1600W or 240V 2800W
- Heating
- Triple low-watt-density element
- Pump
- Optional recirculation pump
- Grain basket
- High-flow, dual-height false bottom
- Material
- 304 stainless
What it is not good at
Community reports consistently describe a learning curve getting it seated correctly, and a badly seated plate channels.
Who it is for
Brewers who want the lautering element supplied
FAQ
Questions brewers actually ask
What does a false bottom do in a mash tun?
It holds the grain above the vessel's outlet so wort can drain through without the grain following it. The plate is not the real filter, though -- its perforations are too coarse for that. What actually filters is the grain bed itself, with the husks forming a matrix that catches fines, and the plate simply supports that bed.
Is a domed false bottom better than a flat one?
Yes, for two separate reasons. A dome is an arch, so it carries the weight of fifteen pounds of grain and water without bowing, where a flat plate sags in the middle and causes uneven drainage. And a dome follows the vessel's base contour more closely, which leaves less unreachable wort as dead space beneath it.
How do I size a false bottom?
Measure the vessel's internal diameter rather than relying on its nominal capacity, because kettles of the same stated volume vary. You want a snug fit: a visible gap at the edge lets grain pour round and under the plate, which blocks the outlet and defeats the whole purpose. Slightly undersized with a gasket beats loose.
Can I use a stainless braid instead of a false bottom?
Yes, and it is the standard budget solution for a cooler mash tun. A length of braided stainless hose sleeve on the outlet filters surprisingly well. Its weaknesses are that a heavy grain bed can crush it flat and it is harder to clean thoroughly than a plate you can lift out and inspect.
Why does my mash drain stop partway through?
Usually a compacted bed rather than a hardware fault. The most common underlying cause is a crush that shredded the husks -- typically from running a mill at full drill speed -- leaving the bed with no filter matrix so it packs into a plug. Stir it, drain more slowly, and add rice hulls if your bill is heavy in wheat or flaked adjuncts.
Read next
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Mash Tun vs Lauter Tun
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