I am cycle 350 and 15 dupes, a lot of things are happening and I kinda have some long pipes too but I think it shouldn't matter.
Every time a dupe finishing a liquit pipe games complete freezes for few seconds, if there are a lot of work in queue it will lag even more. I restricted paths and I kinda swept most of the debris because I thought the lag is about that. Its like you are reiterating all the existing pipes on the map and add a new one, hope you are not using only one giant list for all the pipes in the world.
Also I have 8 gb ram and it eats like 40%, isn't that too much? As I mentioned the game runs good until I build liquid pipes, and I have a ton of gas vents and it doesn't lag at all.
I don't wanna restart a new world, the game is looooong as it is and I don't wanna build pipes with the debugger, please look into it for a future fix if someone has this trouble too.
Maybe is something specific to my world or my specs. CPU is strong, I am not worrying about that but GPU is weak, so I am not sure where the calculations are done for the liquid pipes.
Edit: some typos
Steps to Reproduce
Perfomance dropped with time but is only about liquid pipes.
This issue has not been confirmed by a developer yet.