Cookware

Lauter Tun

A vessel with a false bottom that separates sweet wort from spent grain in brewing.

A lauter tun is a brewing vessel fitted with a slotted false bottom or screen that lets liquid drain while holding back the grain bed. After mashing, the sweet wort is run off and the grains are rinsed with hot water in a step called sparging. The grain bed itself acts as a natural filter, clarifying the wort as it drains.

A lauter tun is the dedicated vessel in which sweet wort is separated from the spent grain bed after the mash. In the brewing sequence it sits between the mash tun—where starches have been converted to fermentable sugars—and the brew kettle, where the wort is boiled with hops. The word "lauter" comes from the German for "clear" or "fine," and that is the vessel's job in one word: to deliver clear wort.

What makes a lauter tun a lauter tun is not the vessel itself but the perforated barrier inside it. A false bottom, slotted manifold, or bazooka screen sits a few inches above the floor, supporting the grain while letting liquid pass through. Lautering relies on grain-bed filtration: the compacted husk-and-grist bed itself becomes the filter media, trapping proteins, husk fragments, and grain fines. A rotating rake (in commercial tuns) or careful vorlauf (in home setups) keeps that bed loose and even so wort can flow uniformly without channeling or compacting into an impermeable mass.

The vessel matters because wort clarity, pH, and tannin levels are all set here. Cloudy wort carries starches and polyphenols that produce haze, astringency, and off-flavors in the finished beer. A well-run lauter tun maximizes sugar extraction while keeping the bed intact and the runoff bright.

Alternatives

Mash Tun With A False BottomGrain Bag In The KettleCooler With A Slotted Manifold

Types & varieties

Cylindrical lauter tun with rake

Commercial standard; rotating rake blades gently cut the grain bed to prevent channeling and compaction.

Rectangular lauter tun

Older or smaller-scale design using a slotted manifold or false bottom, often with manual raking.

Combined Mash-Lauter Tun (MLT)

Single vessel that performs both mashing and lautering; common in homebrewing and small brewpubs.

Flat false bottom

A perforated dome or plate with a raised lip that supports the grain bed evenly while letting wort through.

Slotted manifold (or bazooka screen)

Long perforated pipes that sit above the vessel floor; an alternative to a flat false bottom with less dead space.

HERMS / RIMS system

Recirculating setups where the lauter tun is integrated with a heat exchanger, so wort is continuously heated and returned to the bed.

Cooler-based MLT

Homebrew favorite: an insulated beverage cooler fitted with a false bottom or manifold and a ball valve.

Converted keg MLT

A ball-valved keg repurposed with a copper or stainless manifold for small-batch all-grain brewing.

The Three Phases of Lautering

Lautering is not a single action but a sequence, and each phase has a different goal. Skipping or rushing any of them is the most common source of off-spec wort.

Vorlauf (recirculation): The first wort drawn from the bed is cloudy with grain particles, proteins, and husk dust. It is pumped or poured back onto the top of the bed until it runs clear. This both clarifies the wort and settles a tight, even filter bed.
Runoff: Once the wort is bright, collection begins. Flow should be slow and steady—roughly 1 quart per minute per square foot of grain bed—so sugars are extracted without compacting the husks. The liquid level above the grain must never drop, or the bed can pull dry and seal shut.
Sparging: Hot water (168–170°F / 76–77°C) is rinsed slowly over the grain bed to leach out the remaining sugars. Below 150°F, enzymatic activity stalls and viscosity rises; above 170°F, you begin extracting harsh tannins from the husks. The goal is to collect wort at roughly the same gravity as the first runnings until the target pre-boil volume is reached.

False Bottom vs. Manifold

Both designs retain grain while passing wort, but they behave very differently in practice. The choice shapes cleaning time, dead space, and how forgiving the system is when something goes wrong.

A flat false bottom is a perforated dome or plate with a raised lip. It supports the entire grain bed evenly, which makes for a stable filter, but it creates a dead space underneath that holds wort and can harbor debris if not cleaned thoroughly.
A slotted manifold (or "bazooka screen") is a ring or cross of perforated pipe that sits just above the outlet. It has almost no dead space, so extraction efficiency is slightly higher and cleaning is faster, but it does less to support the grain bed and is more prone to channeling on a poorly set mash.
For wheat-, oat-, or rye-heavy grists, a manifold often outperforms a flat false bottom because it resists clogging from the sticky, floury husks. Pairing either design with rice hulls in the grist is the most reliable insurance against a stuck sparge.

Common uses

Separating sweet wort from the spent grain bed after mashingRecirculating first runnings (vorlauf) until wort runs clearSparging—rinsing the grain bed with hot water to extract remaining sugarsProviding a final wort clarification step before transfer to the boil kettleHolding wort at temperature during the runoff phase

Tips & pitfalls

Always recirculate the first runnings until the wort runs clear; cloudy wort carries starches and polyphenols that cause haze and astringency in the finished beer.
Start the runoff slowly and never let the grain bed dry out—a steady liquid level above the grain keeps the filter bed open and prevents a stuck sparge.
Target a flow rate of roughly 1 quart per minute per square foot of grain bed; faster flow compacts the husks, slower flow lets the bed set unevenly.
Hold sparge water at 168–170°F. Too hot extracts tannins; too cool stalls enzymatic conversion and raises wort viscosity, often triggering a stuck mash.
Do not stir or disturb the grain bed once it is set. The husks are the filter media—let the rake or the vorlauf settle them, and resist the urge to "help" with a spoon.
If runoff stalls, pause briefly and gently rake only the top of the bed to relieve compaction; never blast a stuck sparge with full flow, which packs the bed tighter.
For wheat- or oat-heavy grists, add an ounce or two of rice hulls to the grain bill to improve bed porosity and prevent the sparge from sticking.
Drain the grain bed fully only after runoff is complete; pulling the bed dry mid-run exposes hot wort to oxygen and can dull hop and malt character in the finished beer.

Good to know

Also called: Lauter (from German, meaning "clear" or "fine")
Primary function: Separates sweet wort from spent grain after mashing
Key component: False bottom (perforated plate, screen, or slotted manifold)
Step in brewing: Follows mashing, precedes the boil
Capacity range: From 5–10 gallon homebrew units to commercial vessels of many barrels
Grain bed depth: Typically 12–18 inches in commercial tuns for a proper filter bed
Operating temperature: Wort held at 168–170°F (76–77°C) during sparging
Origin: German and Central European lager-brewing tradition