Factorio Forums

Image of the problem: https://imgur.com/M5IAsaz

Quick description:
An underground pipe does not continue the flow of a liquid to it's counterpart 5 tiles away. When hovered over shows wrong graphics which helped me find the cause for a flow disruption to my chemical plants. The pipe was placed in 0.17.0 but flow was not connected after an update to 0.17.6 The error was noticed in [0.17.6].


Long description.
I was working on setting up my chemical plants for light oil to gas cracking. After placing all the pipes, and thanks to the new liquid previews I was quickly able to see that I was NOT mixing my liquids, before even connecting the pipes to the liquid storage. Everything looked OK, ready for water and light oil to be connected. After making the connections and walking away, my brother who plays on the same map as me told me to check on the cracking, as he saw that only the first set was working. I have 5 sets of 5, and think I am prepared for the future.

Walking back over, I saw what you can now see in the image posted above. Fluid was blocked by the pipe my mouse is hovering over. The one with the green graphics around it. The bottom of the pair had 99 water in it, the top one had 0. All the chemical plants above the picture have some level of water in them and light oil was not a problem.

I have since checked all the other pipes in my system, about 500 pairs of them, maybe more. None of them showed the same problem. I can't tell you how to recreate the problem because I am not sure what caused the problem in the first place.
I managed to fix the problem on my end by removing and replacing the pipe causing the problem.

These graphics are for a disconnected underground connection. That should occur in some enforced mixing but that is not your case indeed. I will need the save though, ideally the previous version too.

As you requested, here are the saves.
Naming code: 17 = major version. M2 = Multiplayer, 2 players. M2.1 = updated version post desync issues. My brother kept getting de-synchronised from the game so we saved and updated to a new save with the 0.17.6 version.
First the 17M2 is from before the error. We updated from 17.0 to the new save because of desync issues.
The save below this text is from after the error. In this version we played on 0.17.6, solving 100% of our de-synchronisation issues.

Maybe related to viewtopic.php?f=7&t=67057

Unfortunately your saves are of little help as the first one does not even have the setup where your problem is and the second has all connections ok.

I have made some changes in 17.7. that improved this mechanic, which is why you are not getting desynced anymore. But the disconnection still exists - it is the same as in the linked issue. And I can't find what was the source of it. At some point the game must have thought that those two underground pipes can't connect (which should only happen, and can happen, due to mixing) and split the fluid systems along that connection. As I was asking at the other issue, can you please help me identify where this has originated? For one, you did not write when exactly the desync occurred.

Cases where the pipes should get into this disconnected state (marked by the red color between them) is when there are two underground pipes with a different fluid that would connect, but there is another underground pipe between them preventing the connection. But once the middle one is removed/rotated/replaced the disconnected state is created. And there were various bugs around it like this viewtopic.php?f=47&t=66118.
So can you recall if something of that sort happened there in the past?

I am sorry to hear that the saves are of no use, sadly I have no save game state closer to the bug occurring.

I have talked with my brother, with whom I play on the map, and we can not figure out why the desyncs happened in the first place. All we know is that since we went from 17.0 to 17.6 we've had 0 issues of that kind.

As for the cases of fluid mixing, I have learned to be extra, extra careful when placing down pipes or underground pipes in 0.14, 0.15 and 0.16. So I can not recall any form of fluid mixing potentially occurring. This seems reinforced by the fact that the disconnect of the pipes happened AFTER there had been stable flow of water through the pipes beyond.

I wish I was clearer of memory so I could help you better, but in almost 800 hours of Factorio play, this is the first time that I personally witnessed a bug.

No worries, thanks for the help! It is fixed now. Let me know if you run into other issues but hopefully it will be all ok.