Factorio Forums

Underground pipe ghosts delete pipe ghost when placed both sides of it.
Placing underground pipe ghosts first then pipe ghost inbetween works normal.

Thanks for the report. Pipe-to-ground placement that finishes a pair is expected to remove all pipes in between if there are pipes on every tile between pipe-to-ground ends and pipes in between have no perpendicular connections. This behavior is primarily useful when you have long sections of pipes and you are replacing them with pipe-to-grounds.

Issue here is slightly different, ghost pipes do not connect to nearby pipes so they do not know they should be protected (as they would have a perpendicular connection after revive). That would be a huge code change and i am not going to do that in 1.1.x. This issue is already fixed for 1.2.0.