I struggle to understand why there isn't a manual override in place for the gas pipeline.

[MineralMan]

7. I did some additional searching.

Apparently, there are no barriers. The products are shipped serially. A mixed interface between two products is created, which must be handled separately. For example, 93 octane gasoline might be shipped behind 87 octane gasoline. Between the two, there is an area or volume of fluid where they intermix during transit. At the receiving terminal, the mixed material is shunted off for reprocessing. The two types of gasoline are shunted off for storage separately.

Add diesel, jet fuel, and heating oil for shipment and each will have a mixed interface area that travels through the pipeline, which must be separated at the terminal. Timing will be very important, and automated testing will be needed to detect such interface areas and shunt them out of the stream, leaving only the desired product to be shunted into appropriate storage.

A lot of that can be automated, but doing it manually would be quite difficult and take far more time than automated testing to detect such liquid interfaces.

This is a very interesting thing to think about and explore. I don't have time right now to look into it in depth. It's a very complicated system, really.