Sandustry Filter

The Sandustry Filter is a conveyor belt you can configure to let one chosen resource drop through it while everything else keeps moving - unlocked at Tier 1 research for 250 Gold. Set it to Allow to pass exactly one resource, or Block to pass everything except one resource. The single most important thing to know: a basic Filter only sorts solids - it never stops liquids or gases, which is why water keeps "leaking" through wet-sand filters. This guide covers setup, the vertical filter trick, multi-stage arrays, and the clogs and leaks that trip up most new players.

How Allow and Block work

A Filter behaves like a normal conveyor belt for every resource it is not configured to catch. When you select the resource to filter:

• Allow passes only that one resource down through the belt; everything else rides on. Allow Gold under a Shaker output and gold drops through while sand and Residue continue along the belt.
• Block is the inverse: the chosen resource stays put and piles up on the belt, while everything else passes. Block Redsand on a mixed line and only red sand is held back.

Blocked material is not redirected - it simply stops and accumulates. That is why every blocked output needs somewhere to go: a side belt, a launcher, or a chute. A filter with no overflow path is a future clog. Basic Filters also obey a single-resource rule - one filter, one resource, in either mode. To separate several resources you stack filters, which is where the fun begins.

Unlocking the Filter and the Advanced Filter

The Filter is a Tier 1 research node costing 250 Gold - roughly your fourth to sixth research after the Shaker (20 Gold) and Logistics (30 Gold) get your first gold line running. It is cheap for how much it changes your factory.

The Advanced Filter arrives much later at Tier 4 for 1,500 Gold and extends filtering to solids, liquids and gases. Exactly how its multi-resource selection works is still being documented in Early Access: the official research page says it filters "multiple element types at once", while the official beginner's guide says it still follows the single-resource rule. Treat the details as version-sensitive until you test in your own build verify in current build.

Vertical filters: the trick nobody tells you

Filters do not have to lie flat. Select a placed filter and press R to rotate it vertical, and it becomes a wall that either blocks or passes resources sideways. Both basic and Advanced Filters rotate.

This is one of the most-asked questions in the Steam discussions - players find vertical filters in screenshots and blueprints, search the build menu, and find nothing. The control hint is easy to miss: with a filter selected, look at the bottom-left of the screen for the rotation key. There is no tutorial for it, and players report finishing the entire game without discovering it. If you take one thing from this guide: select, press R.

Vertical filters gate falling material - for example, sealing a shaft so red sand cannot drift onto your main belt while sorted material drops past.

Drop-through arrays and smart layouts

Because each filter catches exactly one resource, real sorting uses rows of stacked filters that material drops through:

1. Drop a mixed pile onto a column of filters, one under another.
2. Each layer catches one resource type and lets the rest fall to the next.
3. Order layers by density, catching the densest first - dense material sits at the bottom of a mixed pile, so Allow Gold at the top of the column separates cleanest from a sand-gold mix.

Community-favorite patterns worth copying:

• Filter under Shaker output - the first place every factory needs one: split gold from sand and Residue right where they are produced, before the mix spreads.
• Overflow-first rule - every Allow and Block output needs a destination; pair each filter row with a side exit for what it holds back.
• Rate limiter - a single solid block one tile above a belt input stops surges of material from overwhelming your filter rows; material waits for a gap instead of burying the line.
• Reflow loops - a launcher that throws unprocessed overflow back over the filters gives every pixel a second pass.
• Wet-sand line - Block Residue on the main Shaker line, Allow Wet Sand on a parallel line, and use a pump outlet dripping water onto seeds sitting on a filter to wet them in place.

Why water leaks through your wet sand filter

Because the basic Filter does not block liquids - at all. The official data is explicit: Blocks Liquid: No, Blocks Gas: No. Setting a filter to "Wet Sand" only changes which solid drops through; the filter never becomes a wall for water. This is the single most common misunderstanding with filters.

For liquids you need the fluids toolkit: Pipes, Pumps and Liquid Vents (Tier 3, 1,250 Gold). A Liquid Vent always sucks the nearest liquid regardless of what you wanted, so run dedicated lines per liquid and split them early. Also watch diagonal gaps: two blocks that only touch at a corner let liquid slip through what looks like a sealed wall. The Advanced Filter extends filtering to liquids, but its configuration UI is still thin on official documentation verify in current build.

When pixels jam or slip through

Two failure modes cause most "filter not working" reports:

• Jams: a resource changes state while inside the filter - sand or seeds meeting falling water turn into wet sand or wet seeds mid-crossing - and the transformed pixel no longer matches the allow rule, so it sticks in place forever, neither dropping nor riding on. The fix is manual clearing plus re-arranging so state changes happen before or after the filter, not inside it.
• Corner leaks: resources also escape through diagonal contact points between blocks; seal corners when a filter array must be airtight.

One more oddity worth knowing: occasionally a single pixel of a blocked resource appears on the wrong side of a filter - for example, Dry Amethelis sneaking past a filter set to block it. The community-traced cause is a state transformation completing inside the filter (the pixel dried in transit). Google's official wiki lists no known bugs, so treat this as a known-in-community quirk: add a second catch filter downstream as a failsafe rather than trusting a single layer.