Sandustry Filter: Sorting and Jam Prevention

Quick Answer

A basic sandustry filter acts like a conveyor for ordinary material while allowing the configured material to fall through. In Allow mode, the selected solid falls and everything else continues; in Block mode, everything except the selected solid is eligible to fall. Configure one material per basic Filter, separate dense materials early, and keep Water away from solids that can transform while passing through. Always provide space below and an accessible overflow, because a blocked exit or mid-filter reaction can create a jam.

Choose Allow or Block Deliberately

Allow is easiest to reason about when one valuable or problematic material needs its own branch. Select that material, give it a clear chute below, and let the remaining stream continue horizontally. Block is useful when one material must stay on the conveyor while everything else drops. The two modes describe what can fall, not a magical inventory transfer.

Goal	Setting	What falls through	What continues like a belt
Extract Gold	Allow Gold	Gold	Other materials
Keep one material on the line	Block selected material	Other eligible materials	Selected material
Split two desired materials	Multiple stages	One selection at each stage	The remainder
Handle liquids or gases	Advanced Filter or another verified system	Depends on current configuration	Basic Filter is documented for solids

The official beginner guide explains that the basic Filter uses a single resource selection for both modes. Do not expect one block to Allow two materials at once. Chain filters when multiple outputs need separate routes, and ensure the first branch does not starve the second. The current Research page says the Advanced Filter can handle multiple element types, including liquids and gases, but confirm its live interface before redesigning a working line.

Treat every new branch as a separate test. Feed a small known batch, confirm the selected material reaches the lower chute, and verify that the remainder continues without accumulating above the block. This makes configuration errors distinct from physical congestion before the sorter joins a live factory.

Sort with Density in Mind

The dedicated Filter page warns that a tall mixed pile can keep lighter pixels above denser ones and away from the opening. It recommends filtering denser material first because that material naturally settles near the bottom. Gold is the official example: allowing it through early gives it a better chance to reach the Filter beneath Sand. A shallow, moving stream is easier to sort than a storage tower dragged across one block.

Reduce pile depth before adding more filter stages. Spread intake, meter batches, or add upstream capacity so pixels remain close to the filtering surface. The page describes a short pull effect near the Filter but explicitly says it cannot always be relied upon. Design for gravity and clear access rather than a best-case rescue behavior.

Identify every material in the incoming stream.
Choose the densest or most important output for the first branch.
Configure one basic Filter and open the space below it.
Route the remainder to the next Filter or a safe overflow.
Test a mixed batch and inspect what remains on top.
Add stages only after the first branch clears consistently.

Prevent Material-Change Jams

An allowed pixel can change into a disallowed pixel while it is passing through the Filter. The official page gives Sand becoming Wet Sand and Spores becoming Wet Spores when Water is present as examples. The changed material may become stuck instead of falling or moving onward. Keep Water away from basic solid-sorting points and perform wetting in a dedicated upstream or downstream module.

If a Filter jams, stop intake before manually clearing it. Inspect whether the stuck pixel has a different label from the configured input and whether liquid is crossing the block. Repair the reaction boundary instead of repeatedly removing the symptom. A maintenance gap beneath the Filter turns this from a demolition job into a quick inspection.

Build a Safe Overflow

The area below a Filter must not be a sealed solid floor unless trapping material is intentional and understood. The official page notes a specialized case involving trapped Cinders and ignition, but that is not a default sorting design. For ordinary operation, the falling branch needs a chute, conveyor, buffer, or collection path. The horizontal remainder also needs somewhere to go when the next machine stops.

Use a visible overflow that cannot rejoin the intake by accident. A full output should create an obvious pile in a safe buffer, not push material back through multiple stages. Mark overflow as a condition to investigate rather than permanent storage. This design makes it possible to tell capacity limits from incorrect Allow or Block configuration.

Troubleshooting Checklist

Selected material stays on top: reduce pile depth and filter denser material earlier.
Everything continues horizontally: recheck mode, selected material, and open space below.
Material sticks inside: look for Water or another reaction changing its type.
Output branch fills immediately: clear its buffer before adding more intake.
Two materials must share a branch: use sequential Filters or verify the Advanced Filter interface.
Behavior changed after a patch: compare the live tooltip with the official wiki and record the version.

Do not solve a routing error by copying an unverified “perfect ratio.” The exact load depends on the physical stream, terrain, and upstream process. Observe whether the target material reaches the filter surface and whether both exits remain open. That evidence is more useful than a nominal belt count without version context.

Sources

This independent guide is not affiliated with Lantto Games, Hooded Horse, Valve, or the Sandustry Official Wiki.