Basic Fluids

Lore & Background

In the cramped, grid-lined world of the Oxygen Not Included colony, fluids are both lifeline and hazard. Water carries heat, oil can ignite, and pressurized steam can crack a bulkhead. The research codex entry for Basic Fluids reflects a practical, almost weary tone: the colonists who first cracked open the discipline were not theorists but engineers who watched a water leak flood a lower deck and realized that gravity alone was not a system. The blueprint distills that hard-won lesson into teachable principles—density, flow rate, pressure differentials, and the behavior of liquids in confined, multi-layered environments.

The game's 2D cross-section view makes fluid behavior viscerally clear: a column of water pressing down on a lower room, a thin film of oil sliding along a ceiling, a bubble of gas trapped in a pipe. Basic Fluids is the conceptual key that lets the player stop watching these phenomena and start directing them. It is the moment the colony transitions from a collection of rooms and ducts into an engineered system with intent.

Fans often describe unlocking Basic Fluids as the first true 'aha' moment in a new playthrough. Up to that point, the colony is a survival puzzle. After it, the colony becomes a machine, and the player becomes its engineer.

In Their Own Story

The Research Station hummed its low, metallic drone. Kira set her tablet down, the cursor blinking over the single blueprint icon: a stylized droplet bisected by a horizontal line, the universal mark for Basic Fluids. Behind her, the lower deck was already sweating condensation off the rock walls, a thin rivulet tracing the hex grid toward the drainage channel she'd hastily lined with scrap metal.

"You sure about this one?" asked Dax, leaning over her shoulder with a mug of lukewarm reconstituted coffee. "Once we start pumping, we can't just… let the water sit where it wants to sit."

Kira didn't look up. She tapped Confirm. The progress bar filled with the soft chime of knowledge transferring.

"No," she said. "We can't. That's the whole point."

Reader's Guide

Basic Fluids is a single Tier 1 research blueprint in the Fluids / Engineering branch. It has no prerequisite blueprints and is available as soon as a Research Station is built and a colonist is assigned.

Tier 1 – Fluids: Basic Fluids — Unlocks the foundational fluid-handling capability for the colony. This grants access to the Fluid Pump, the most basic active liquid mover in the game. The Fluid Pump draws liquid from one connected pipe or room and pushes it into an adjacent one, allowing the player to circulate water, oil, or other fluids against gravity and through multi-level infrastructure. This is the first time the colony can actively route liquids rather than relying on passive gravity flow.

Practical impact: Once unlocked, the player can build closed-loop water circulation, feed water to a water generator or reclaimer, and begin managing heat transfer via fluid movement. It is a hard prerequisite for every subsequent fluid blueprint—hydraulic systems, advanced pumping, and fluid-based power generation all trace their dependency chain back to this single entry.

Tip: Research this as early as possible in a new colony. Even before you build a full water loop, having the Fluid Pump available lets you drain a flooded room or top up a water tank without waiting for a rain cycle, which saves valuable early-game time.

Did You Know?

• Basic Fluids is one of the very first blueprints a new colony can research, making it a near-universal early milestone that virtually every player encounters in their first few hours.
• In the game's 2D cross-section view, fluid behavior is rendered in real time, so the moment Basic Fluids is unlocked and a pump is placed, players can visually watch liquid columns shift and pressurize across multiple le
• The Fluid Pump unlocked by Basic Fluids is the only Tier 1 fluid machine, meaning the entire hydraulic progression tree in the game grows from this single starting node.
• Because ONI simulates fluid density and pressure, a poorly placed pump after unlocking Basic Fluids can create a feedback loop that floods a room with superheated water—a common and memorable early-game lesson.