Factorio Forums

When an underground pipe contains a fluid, and the "to ground" side is adjacent to a pipe that is part of an empty fluid system assigned to a different fluid, reversing the underground pipe causes the new fluid to override the old one. To demonstrate the issue and why this is a problem, see the following screenshots.

Before:
After placing an underground pipe section in the reverse direction over the existing underground pipe section:
Note that the crude oil has overwritten the expected chemical plant input of water as shown in the details pane on the right. If we delete the piping and try to attach a water pipe to the water input, the anti-mixer system prevents the connection because it thinks the chemical plant actually wants crude oil. The only ways to fix this are to repeat the bug to overwrite the crude oil input with the correct water, or remove and replace the chemical plant.

I watched EndivaGER in Twitch and he had the same issue
here you can see mixing sulfur acid into wrong pipe

he is playing wit 0.17.4
https://clips.twitch.tv/KathishGiftedLouseCoolStoryBob

Thank you for the report. I have fixed it for the next version. Problem was that the new pipe had no fluid conflict, but then it cloned the fluid from the replaced one.