Alchemy Factory Filter Splitter Guide
Early automation feels smooth until rotten logs, mushrooms, and mixed outputs show up and suddenly everything jams. This guide clears up how the Filter Splitter actually works and why it becomes mandatory once you move into advanced fertilizer and late game production.
How The Filter Splitter Works
The Filter Splitter lets you separate one specific item from a mixed output belt. One item goes out the filtered port and everything else goes out the normal port.
You choose the filtered item in the splitter menu. The filtered item always exits from the highlighted output, while all other items continue through the remaining output.
If either side backs up, the entire splitter stops. That detail matters more than it sounds.
Why You Need The Filter Splitter
The biggest reason players unlock the Filter Splitter is rotten logs. Rotten logs output planks and mushrooms at the same time. Without filtering, automation breaks fast.
Advanced fertilizer requires mushrooms. Planks are a byproduct that must be consumed or discarded. The Filter Splitter is the only clean way to do this without babysitting belts.
Common use cases include:
Separating mushrooms from rotten log planks
Sending mushrooms to an assembler for advanced fertilizer
Sending planks to furnaces, quicklime, plant ash, storage, or trash
Preventing full belt lockups during long runs
Once you automate fertilizer, the Filter Splitter stops being optional.
Using The Top Yellow Output Correctly
The filtered item exits from the highlighted output, which many players call the yellow output. This output can be vertical or horizontal depending on orientation.
If you cannot pull items from it, the splitter is likely facing the wrong direction.
To fix this:
Press T to rotate the splitter orientation
Use lab stands or lifts to access vertical outputs
Make sure the filtered output has somewhere to go
If the filtered side is blocked, nothing moves.
Preventing Belt Lockups
The most common mistake is forgetting about the non filtered output. If planks fill up and stop moving, mushrooms stop too.
You must always consume or dump the leftover item.
Reliable solutions include:
Sending planks into furnaces as fuel
Feeding planks into quicklime or plant ash chains
Using a buffer storage box that you clear occasionally
Sending overflow into a trash can
If one side stalls, the whole line dies.
Filter Splitter And Advanced Fertilizer
Advanced fertilizer is made by combining basic fertilizer and mushrooms in an assembler. Mushrooms come from rotten logs, which means mixed outputs.
A clean setup looks like this:
Rotten logs into log cutter
Output into Filter Splitter
Mushrooms to fertilizer assembler
Planks to fuel, quicklime, ash, or disposal
With advanced fertilizer, one nursery can replace several basic fertilizer nurseries. That is why the splitter matters so much.
Helpful Tips Before You Automate
Always test splitters with a storage box first
Never let both outputs feed into the same belt
Use priority splitters after filters if needed
Build vertically if floor space is tight
Expect to rebuild this once or twice, it is normal
Automation in Alchemy Factory rewards patience, not perfection.
Final Blurb
The Filter Splitter is one of those tools that feels confusing once and obvious forever after. Once you understand that both outputs must stay clear, it becomes the backbone of fertilizer, fuel, and late game automation. If your factory keeps freezing, the splitter is usually the missing piece.
FAQ
Do I need a Filter Splitter for advanced fertilizer
Yes. Fully automated advanced fertilizer requires separating mushrooms from rotten log planks.
Why does my splitter stop working randomly
One of the outputs is blocked. Both sides must stay clear or the splitter halts.
How do I pull items from the top output
Rotate the splitter with T and use lab stands or lifts to access vertical ports.
Can I filter any item
Yes. Any item that appears in the splitter menu can be filtered.
What should I do with extra planks
Burn them, process them, store them, or trash them. Just never let them back up.
