If you’ve ever lost a colony to a catastrophic chlorine flood or watched helplessly as your water system backed up into your ranch—congratulations, you’ve experienced the joy (and pain) of how plumbing works in Oxygen Not Included. This survival simulation game by Klei Entertainment features a realistic fluid dynamics system that’s both powerful and unforgiving. Unlike most games where liquids magically disappear, ONI demands strategic planning, pressure awareness, and smart pipe design. In this guide, you’ll learn exactly how the plumbing system functions, why your base keeps flooding, and how to build efficient, scalable liquid networks—even as a beginner.
What Makes ONI’s Plumbing System Unique?
Oxygen Not Included doesn’t use “simple pipes.” Instead, it simulates liquid physics based on pressure, temperature, and flow rate—inspired loosely by real-world fluid dynamics (though simplified for gameplay). Every liquid in ONI—water, polluted water, molten metal, chlorine, etc.—has distinct properties like viscosity, boiling point, and pressure tolerance.
Unlike Minecraft’s redstone or RimWorld’s water mods, ONI’s plumbing is core to survival. A single misconnected pipe can doom your entire colony in minutes.
💡 Fun Fact: Each pipe in ONI can hold up to 10 kg of liquid per tile. Exceed that, and backpressure builds—which can cause liquid to spill into adjacent tiles or reverse flow.
How Does Liquid Flow in ONI Pipes?
Understanding liquid flow direction is critical. ONI uses a pressure-based priority system, not gravity (though gravity affects storage containers and open liquids).
Key Rules of Flow:
- Liquids move from high-pressure to low-pressure tiles.
- Pipe priority is set by automation sensors or manual pipe priorities (right-click a pipe → “Set Priority”).
- Pumps always push liquid out, regardless of pressure—but they can’t pull liquid through blocked or full pipes.
- Liquid vents and filters only work when there’s space beyond them.
Example:
If you connect a water pump to a full reservoir, the pump won’t activate, even if your base is dry. Why? Because there’s no place for the liquid to go. Always ensure your output has room!
Step-by-Step: Building a Basic Water System
Let’s build a reliable, beginner-friendly water loop for your early-game base.
Materials Needed:
- 1 Water Pump
- 1 Liquid Vent
- Pipes (Regular or Insulated)
- 1 Storage Tank (or open tile)
Steps:
- Place the Water Pump in your water source (e.g., a pool of clean water).
- Lay pipes from the pump to your desired destination (e.g., your ranch or electrolyzer).
- Install a Liquid Vent at the endpoint, pointing into a room or storage area.
- Right-click the vent → Set to “Water” only to prevent contamination.
- Add a Storage Tank nearby to buffer excess liquid and stabilize pressure.
🛠️ Pro Tip: Use Insulated Pipes for hot/cold liquids (like molten metal or supercooled water) to prevent heat transfer. Regular pipes equalize temperature with surroundings!
Common Plumbing Mistakes (And How to Fix Them)
❌ Mistake #1: Creating Loops Without Priorities
Liquid gets stuck in circular pipe systems.
✅ Fix: Set pipe priorities (1 = highest) to control flow direction. Use a Pipe Bridge to split flows cleanly without backflow.
❌ Mistake #2: Ignoring Liquid Weight
Chlorine (2.5 kg/L) is heavier than water (1 kg/L). Mixing liquids in same pipe can cause unexpected stacking or blockages.
✅ Fix: Use Filters and Sorters to separate liquids early. Never merge different liquids unless intentional.
❌ Mistake #3: Overloading a Pipe Network
A single pump feeding 10 machines? It’ll bottleneck.
✅ Fix: Use multiple pumps or a liquid reservoir with high capacity to buffer demand spikes.
Advanced Techniques: Mastering Pressure & Automation
Once you’ve grasped the basics, level up with these pro strategies:
Use Liquid Sensors for Smart Control
Place a Liquid Sensor near a storage tank. Set it to trigger when water drops below 500 kg. Connect it to your pump via automation wire—now your pump only runs when needed, saving power.
Create a “Liquid Battery”
Store high-demand liquids (like petroleum or ethanol) in large, insulated reservoirs. This acts like a battery—smooth out supply during peak usage.
Leverage Pipe Bridges for Cross-Traffic
Need to send chlorine and water through the same corridor? Use Pipe Bridges (input on one side, output on the other). They never leak or mix content, even under pressure.
🔍 Did You Know? ONI’s fluid simulation is inspired by real-world hydraulic principles, though simplified. For deeper insight, read about fluid dynamics on Wikipedia .
How to Prevent Disasters: Floods, Backups & Toxic Spills
Your #1 enemy isn’t errant dupes—it’s uncontrolled liquid pressure.
Prevention Checklist:
- ✅ Always leave at least one empty tile downstream of vents/filters.
- ✅ Use Airlocks or Doors to contain chlorine rooms—never vent toxic gas near living quarters!
- ✅ Monitor pipe capacity with the “Show Contents” overlay (default key: F6).
- ✅ Build overflow tanks for emergency drainage (use auto-shutoff valves).
FAQ: How Does Plumbing Work in Oxygen Not Included?
Q1: Why won’t my liquid move through the pipes?
A: Check for backpressure—your destination is full. Also verify pipe priorities and that pumps aren’t blocked. Use the F6 overlay to see liquid amounts per tile.
Q2: Can I mix different liquids in one pipe?
A: Technically yes, but don’t. Heavier liquids sink, causing clogs. Always use Filters or separate pipe networks.
Q3: Do pipes have a flow limit?
A: Yes! Each pipe segment transfers 10 kg per second max under ideal pressure. Use parallel pipes for high-demand systems (e.g., metal refineries).
Q4: How do I delete or clear a pipe full of liquid?
A: You can’t delete a full pipe. First, drain it using a vent or pump, then deconstruct. Or use the Deconstructor building (late-game) to auto-drain.
Q5: Why does my chlorine keep leaking into my base?
A: Chlorine vents require empty space to emit gas. If the room is full of gas or blocked, pressure builds and leaks occur. Always vent into dedicated, sealed rooms with gas pumps.
Q6: Are insulated pipes worth it?
A: Absolutely—if dealing with extreme temps. Regular pipes will heat/cool adjacent tiles, potentially melting your base or freezing your crops.
Conclusion: Master Plumbing, Master Your Colony
Understanding how plumbing works in Oxygen Not Included isn’t just about moving liquids—it’s about survival, efficiency, and scalability. With smart pipe design, pressure awareness, and automation, you’ll transform chaotic floods into smooth, self-regulating systems.
Your dupes depend on you. One well-placed pipe can mean the difference between a thriving colony and a chlorine-filled tomb.
👉 Found this guide helpful? Share it with your fellow ONI players on Reddit, Twitter, or your Discord server! And don’t forget to bookmark this page—it’s your go-to plumbing bible for every ONI run.
Happy piping, Spaceman! 🚀
Leave a Reply