Lauter tun design – the unsung hero of brewhouse yield and clarity

Brewers often obsess over hop additions and yeast strains, but ask any production manager about their biggest daily frustration, and they will likely point to the lauter tun. “Why does my runoff slow down halfway through?” is a search query we see repeatedly from craft brewery engineers.

The physics of filtration

A lauter tun is not a sieve; it is a dynamic filter bed. As wort drains, fine particles migrate downward, gradually clogging the gaps. If the bed is too shallow, the resistance increases quickly. If the rake speed is wrong, you channel – causing low extract and high turbidity.

Question: “What is the ideal grain bed depth?”

Between 40 and 60 cm for most craft systems. Deeper beds give better clarity but longer runoff times. Shallower beds run faster but risk haze. Our lauter tuns are sized with an aspect ratio (diameter-to-height) that achieves this depth at your standard grist load – not an arbitrary dimension from a stock catalogue.

Question: “How do I prevent stuck mashes?”

Stuck mashes usually come from three design flaws: (1) too fine a false-bottom slot, (2) inadequate underlet pressure, or (3) a rake that does not lift the bed. Our false bottoms use wedge-wire screens with 0.7–1.0 mm slots, customised to your malt analysis. We also include a variable-speed raking system that can gently cut the bed without disturbing the filter layer – and a pressurised underlet line that allows you to reverse flow momentarily to relieve compaction.

Question: “Does a sparge arm make a difference?”

Absolutely. A fixed spray nozzle creates concentrated flow, washing sugars unevenly and leaving pockets of high gravity. Our rotating sparge arms have multiple nozzle angles that cover the entire bed surface with a gentle rain. The rotation speed is adjustable, so you can match the sparge rate to your drainage speed – maintaining a constant 5–8 cm liquid layer above the grain to prevent oxidation and ensure complete rinsing.

Question: “How do I measure lauter efficiency in real time?”

We integrate a digital refractometer in the wort outlet line that continuously displays extract percentage. When the runoff drops below your target threshold (e.g., 2.5°P), the system alerts you to stop sparging – no more guessing and no more over-sparging, which can lead to tannin extraction.

The hidden cost of poor lauter design

A 2% drop in extract recovery means you are paying for grain that ends up as waste. For a 20hL brewhouse producing 500 batches a year, that loss is roughly €8,000–€10,000 annually – just for the sake of a lauter tun that was never optimised for your recipe.

Engineering is about eliminating guesswork
We do not sell standard lauter tuns. We design them around your grist, your target gravity, and your runoff time preference. And we provide a detailed hydraulic calculation that proves the performance before you order.

→ Share your typical grain load (in kg) and desired mash-tun cycle time. We will send a lauter tun specification that includes a predicted runoff curve and clarity data from our test lab.