Underground Pipe

Lore & Background

In the early days of the alien world, the player's first pipe runs were always surface-level: a thin blue line snaking between the boiler, the furnace, and the first few assemblers. It was tidy, but it was also fragile. The moment a second layer of production appeared, pipes began colliding with buildings, and the factory floor turned into a tangle of blue and red threads that no one dared re-route. The Underground Pipe solved that collision without solving the mess. It simply let the pipe disappear beneath whatever stood in the way. A boiler could now have steam entering from below. A wall of stone walls could be crossed without a detour. The factory grew upward and inward, and the pipes grew downward and through, forming a subterranean circulatory system that the player rarely saw but always depended on. Over time, the Underground Pipe became a design philosophy in its own right. Experienced players would route entire fluid networks underground first, then build the machines on top, so that the factory appeared as a clean grid of assemblers and furnaces with no visible plumbing at all. The pipes were there, of course—just hidden, humming quietly under the feet of anyone who walked the factory floor.

In Their Own Story

The night the steam network failed, the factory went silent in a way that felt almost sacred. Every boiler ticked down, every assembler idled, and the great orange glow of the smelters dimmed to embers. Kress, the youngest engineer on the shift, knelt in the dirt and traced the dead pipe back to where it crossed the new iron-wall expansion. A single tile. One tile where a pipe had been placed on top of a wall and simply… stopped. She pulled the Underground Pipe from her belt, pressed it into the gap, and felt the faint click of two pipe ends meeting in the dark. Within seconds the blue line reappeared, and the whole factory shuddered back to life like a heart restarting. No one else noticed. The pipes were just pipes. But Kress pressed her palm flat against the ground above the hidden conduit and felt it thrum, warm and steady, carrying the factory's blood where no one could see.

Reader's Guide

Function: The Underground Pipe is a passive infrastructure tile that allows a pipe connection to pass through (i.e., be placed on top of) any other item—buildings, other pipes, walls, or empty ground. It has no processing role; it simply extends the pipe network. Input / Output: It has no explicit input or output slots. It connects implicitly to any regular pipe on an adjacent tile (up, down, left, right). Fluid enters from one connected pipe and exits through the other, or simply dead-ends if only one connection exists. Speed / Throughput: It imposes no speed penalty. Fluid moves at the standard pipe flow rate determined by the connected pipe network. Power draw: Zero. No electricity, no fuel, no maintenance. Technology: Unlocked by the Pipes technology, available very early in the research tree. Stacking / adjacency quirks: Its defining quirk is that it can be placed on top of any already-placed item, unlike regular pipes which require an empty tile. You can also place regular pipes on top of an Underground Pipe, effectively creating a two-layer pipe at the same location. It cannot be placed in a river or on a cliff face. Pairing: It pairs with regular pipes as its only functional neighbor. In practice it is used to route fluid under boilers, furnaces, assemblers, or walls so that the factory's top-down footprint stays clean. Think of it as the 'duct under the floor' of your factory's plumbing.

Did You Know?

• The Underground Pipe is the only pipe-type item that can be placed directly on top of another placed item, making it the sole way to create a two-layer pipe at a single tile.
• Because it has no power draw and no fuel requirement, a factory can contain thousands of Underground Pipes with zero additional energy cost.
• In large late-game factories, players often build the entire fluid network underground first and then construct machines on top, so the factory surface shows no visible pipes at all.
• The Underground Pipe and regular pipe can coexist on the same tile, allowing a vertical 'stack' of two independent pipe connections at one location.