Factorio Forums

Fluid movement in pipes is visually bugged:
- Horizontal pipe windows, fluid visualization will move vertically
- Vertical pipe windows, fluid visualization will move horizontally
This appears to affect the non-gaseous version of fluids.
It's a bug that's been in the game since 2.0's initial release; this can even be observed in the FFF released 6-19-26 on the animated pump showoff.

Thanks for the report however that is intended. The bubbles move “up” in the window. Flow itself has no direction data and is purely a measure of how much flow it happening within the entire set of pipes.