Sandustry Filters Building Guide

Filters split mixed material streams by density, letting you recover Gold from slag piles, pull RedSand out of sand belts, or stop Lava from reaching a wetting pool. They matter most mid-game when multiple biomes feed one conveyor and community charts become your blueprint language.

How density sorting works

When materials share a tile column, heavier pieces sink and lighter ones rise. Filters automate that process on belts or drop towers: configured tiers pass materials below a density threshold and eject heavier ones sideways (exact behavior follows unlock tier and patch notes).

Community ordering among core materials (light → heavy) commonly lists:

Sand / Wet Sand → Slag → RedSand → Lava → Gold

Steam and Ice behave as fluids, not filter bands—handle them with Pipes and Pumps instead. Amethelis and Burnt Slag sit in mid-game bands documented on Material Ratios.

Sand sorter and filter automation in Sandustry

Common filter setups

Shaker cleanup: Slag sometimes contaminates Wet Sand belts. A filter ejects slag back to burners while wet sand continues to Shaker intake. Without this, slag clogs reduce effective gold yield.

RedSand split: Mining deep layers mixes Sand and RedSand. Filters route redsand to fluxite chains (RedSand and Fluxite) while surface sand returns to the wetting pool.

Lava guard: Lava between redsand and gold density means filter misconfiguration can send lava onto gold belts—or gold into lava pits. Build lava overflow vents and test with small batches before full throughput.

Vertical drop towers

Drop towers feed mixed piles from the top and collect bands at staggered heights. They complement horizontal filters when you have gravity height but limited belt space. Pair towers with Conveyors and Launchers at each collection tray.

Keep tower inputs slow enough that layers form distinctly—flooding the top tile blends bands and defeats sorting. A launcher dribble feed works better than dumping an entire mine cart at once.

Research timing

Filters typically follow basic logistics once mixed materials appear. The Research Priority Tier List places them after Refining 1 and Logistics 1 but before large drone networks—fix purity before scaling volume.

If filters feel optional in the demo’s first biome, they become mandatory once Slag, RedSand, and Lava share logistics (Gold and Slag).

Mistakes to avoid

Feeding filters unsorted Fire or Soil can jam outputs unpredictably. Wetting inside filter lines creates Wet Sand mid-sort, changing density mid-belt. Keep water pipes separate from sand filter inputs unless you deliberately wet downstream.

Document your filter tier settings per belt label—“redsand out left, sand return right”—so expansions do not reverse flows.

Testing filter lines safely

Before connecting a filter output to a live shaker belt, route the eject lane into a temporary chest for one minute of operation. Mixed Wet Sand and Slag in the chest means tiers are wrong; pure slag in the eject chest means the pass lane is safe to merge. This test costs little sand and prevents an hour of digging out a clogged shaker bank.

When Gold appears in the reject lane, your tier is passing heavy material and ejecting light—reverse settings. Gold losses here are silent but expensive in research time.

Documenting filter tiers per belt

Label each filter line on paper or a screenshot: pass lane vs reject lane, target material, destination building. Expansions go wrong when a new branch connects to the reject side by habit. After Early Access patches, re-run the one-minute chest test—density bands for Amethelis or Burnt Slag may shift. Filters fix contamination; they do not replace correct wetting or shaker angles upstream.

When not to filter yet

Single-material belts from a dedicated sand mine to a dedicated wetting pool do not need filters—adding them early slows throughput without benefit. Introduce filters when biomes mix RedSand, Lava, or slag returns into otherwise clean lanes. Puzzle maps with preset mixed streams are the exception; read map docs before copying vanilla filter tiers.

Return to Buildings Hub for drones and pipes that finish sorted lines.