Polluted Water Is Draining Your Colony’s Potential
You’ve just started a new colony in Oxygen Not Included, and everything seems to be going smoothly. Your dupes are digging, building, and breathing. Then you see it: a sickly green puddle spreading across the floor of your base. A dupe walks through it, leaving a trail of germs. Your water supply starts to show contamination warnings. Suddenly, your carefully balanced systems are at risk.
Polluted water is one of the most common and persistent problems in the early to mid-game. It breeds germs, off-gasses polluted oxygen, and can ruin your clean water reserves if not managed. Left unchecked, it becomes a toxic liability that hampers expansion and threatens duplicant health.
But here’s the good news: polluted water isn’t just waste. With the right strategies, it transforms from a problem into a valuable resource. This guide will walk you through every practical method to eliminate, manage, and ultimately profit from the polluted water in your colony.
Understanding the Source of the Problem
Before you can clean up the mess, you need to know where it’s coming from. Polluted water in Oxygen Not Included isn’t a single issue with one solution. It’s a byproduct of your colony’s life cycle, and each source requires a slightly different approach.
The most common culprits are your own duplicants. Lavatories and sinks output polluted water directly. A single bathroom use creates 6.7 kg of polluted water. Without a drainage plan, this will quickly flood your plumbing. Many new players also discover polluted water by digging into slime biomes, which contain natural pockets of the stuff that will pour out if breached.
Other sources include the Sieve byproduct from water filtration, melted Polluted Ice, and certain geysers or vents that output it directly. The key is to identify which sources are active in your colony. Check the plumbing overlay for backed-up bathrooms and look for open pools in explored areas. This diagnosis will tell you which of the following solutions to prioritize.
Your First Emergency Response
If you have a large, free-flowing spill, you need to contain it immediately to prevent it from mixing with your clean water or flooding living areas.
First, use the priority system to direct a dupe to build a tile barrier around the spill. Even a simple row of sandstone tiles can act as a dam. For larger bodies, consider building a pump directly into the polluted water pool. The Bottle Emptier building is another quick fix. Set it to “Auto-Bottle” and specify polluted water, then set a high priority. Dupes will manually mop up the liquid and deposit it into the Emptier, which can output it into a single, contained tile.
For smaller puddles, the Mop command is your best friend. Simply select the mop tool, drag over the puddles, and assign a high priority. Your dupes will clean it up, bottling the polluted water for later disposal or use. Remember to disable any clean water basins from your bottle emptier settings first to avoid cross-contamination.
The Core Solution: Purification and Conversion
Once contained, you have several pathways to permanently deal with polluted water. The method you choose depends on your available technology, resources, and long-term goals.
The Water Sieve: Your Workhorse for Reclamation
The Water Sieve is the most direct and reliable method for converting polluted water into clean water. It’s a mid-game building available after researching Sanitation.
To set up a basic sieve system, you’ll need a closed plumbing loop. Pipe the polluted water from your lavatories and sinks directly into the Liquid Intake port of a Water Sieve. The sieve requires filtration medium, which is most easily obtained from crushing Sandstone or harvesting Sand from certain biomes. The building will output clean water from its output port.
A critical tip: the Water Sieve outputs water at 40°C. If your input polluted water is colder, this can heat up your base over time. A common solution is to run the output pipe through a cold biome or use a Thermo Aquatuner later on to manage temperature. Always plan your plumbing with heat in mind.
Boiling for Sterilization and Elimination
If your goal is complete destruction rather than reclamation, heat is a powerful tool. Polluted water will turn into Steam at 100°C. This method kills all germs and leaves you with steam, which can then be condensed back into sterile, clean water.
You can achieve this by building a dedicated boiler room. Run radiant liquid pipes made of a high thermal conductivity metal, like Aluminum or Gold, through a hot area. The Magma biome is the classic heat source, but an Aquatuner submerged in a liquid bath also works. As the polluted water heats up in the pipes, it will phase-change into steam inside the pipe, which you can then vent into a sealed chamber.
In that chamber, use Steel Aquatuners or simply let the steam touch cold walls to condense it back into water. This method is power and material-intensive but results in 100% germ-free water and can delete large volumes efficiently.
Leveraging the Natural Carbon Skimmer Loop
One of the most elegant solutions uses two buildings together: the Carbon Skimmer and the Water Sieve. This creates a loop that deletes both carbon dioxide and polluted water.
Here’s how it works. A Carbon Skimmer uses water to scrub CO2 from the air, outputting polluted water. If you pipe that polluted water into a Water Sieve, the sieve cleans it and outputs water. You then pipe that water back to the Carbon Skimmer’s input. The only external input needed is the filtration medium for the sieve, and the only output is the deleted CO2.
This loop is a fantastic way to manage atmosphere in your base’s lower levels while also providing a sink for some polluted water. It’s not a solution for large-scale bathroom output, but it’s perfect for maintaining a clean, breathable environment.
Advanced Resource Recovery and Alternative Methods
When you’re ready to move beyond basic cleanup, polluted water becomes a feedstock for advanced systems and resource generation.
Feeding Thirsty Plants and Critters
Several lifeforms in the game don’t just tolerate polluted water—they require it. The Arbor Tree, for example, can be irrigated with polluted water, saving your clean water for other purposes. The Waterweed plant, found in saltwater biomes, also consumes it.
The most famous consumer is the Puft. Pufts breathe polluted oxygen and excrete Slime. If you allow polluted water to sit in an open pit, it will naturally off-gas polluted oxygen. By creating a stable ranch with Pufts in a chamber filled with this gas, you create a conversion chain: Polluted Water -> Polluted Oxygen -> Pufts -> Slime. This slime can then be composted into dirt or used for other processes, turning a waste product into a valuable biological resource.
The Power of Polluted Water Vents
If you’re lucky enough to find a Cool Slush Geyser or a Polluted Water Vent, you’ve struck gold. These geysers output large quantities of cold polluted water periodically. Instead of trying to get rid of it, you should build a containment system around it.
Use insulated tiles to box in the geyser and a liquid pump to pull the water out. The cold output from a Cool Slush Geyser is an incredible early-game coolant. You can run it through radiant pipes in your base to absorb heat, then sieve the now-warmer water for use. This provides cooling, water, and a managed output all in one.
Troubleshooting Common Pitfalls and Mistakes
Even with the right buildings, things can go wrong. Here are solutions to the most frequent issues players face.
If your Water Sieve is backing up, first check its output pipe. Is there a blockage or is the destination tank full? The sieve will not operate if it cannot output the clean water. Next, check the filtration medium supply. Dupes need to deliver sand or regolith to it regularly. Finally, ensure the building itself is not overpressured. It requires the output tile to be in a gas pressure below 2 kg.
Germs are a major concern with polluted water. The Water Sieve does not remove germs; it only converts the water type. If you sieve germy polluted water, you get germy clean water. To solve this, you can either heat the water to 75°C to kill the germs before sieving, or use a Liquid Reservoir. Germs in water stored inside a reservoir will slowly die off over time, especially if the reservoir is in a chlorine-filled room.
Temperature management is the silent killer of many colonies. As mentioned, the Water Sieve outputs at a fixed 40°C. Pumping this warm water into your farms will cook your plants. Always run a temperature check on your water supply lines. Use insulated pipes for long runs, and consider creating a dedicated cooling loop with an Aquatuner and Steam Turbine for late-game stability.
When to Just Let It Evaporate
For very small amounts of polluted water in hard-to-reach places, sometimes the simplest solution is the best. Polluted water will slowly evaporate into polluted oxygen if left in a shallow layer on the floor, especially in warm areas.
You can accelerate this by using a Mesh or Airflow Tile floor. The liquid will sit on it and have more surface area exposed to the air, speeding up evaporation. This is not a solution for bulk amounts, but for the last few kilograms after a mopping operation, it’s a hands-off way to achieve a completely dry floor.
Transforming Waste Into a Strategic Asset
The journey from seeing polluted water as a threat to recognizing it as an opportunity is a milestone in mastering Oxygen Not Included. Your initial goal is containment and prevention of damage. Your mid-game goal shifts to efficient conversion and integration into life support loops, like the bathroom-to-sieve system. Your end-game vision should see polluted water as a key component in complex industrial processes, cooling systems, and ranching operations.
Start by mapping your sources. Set up immediate containment for any spills. Research Sanitation and build a dedicated plumbing loop with a Water Sieve to handle duplicant waste. As you expand, look for ways to integrate it into cooling or resource chains. Finally, keep an eye out for those precious geysers that provide a renewable, manageable supply.
By following these steps, you won’t just get rid of polluted water. You’ll harness it, turning a colony’s headache into one of its most versatile tools for growth and survival.
