So let me suggest a (major) redesign of pipes:
- There are 4 kinds of pipes: Straight pipe, access pipe and junction, bridge.
- Access pipes look kind of like a fire hydrant. They connect the surface with the underground pipe network. Access pipes connect all around. Put 2 access pipes next to each other and they connect. Put a pump next to it and it connects. (Basically how straight pipes are now.)
- Bridges are 1x3 tiles large and are kind of the reverse of under ground belts. They act like access pipes at the end that don't connect to the middle. They connect 2 under ground pipes north-south or west-east while ignoring any under ground pipe in the middle. This allows crossing 2 pipes but creates an obstacle above ground.
- All other pipes are underground.
- Straight pipes connect to the first two unconnected pipes placed next to it. The game has to remember how it connects since in parallel pipes it depends on the order of placement. Junctions connect all around.
- Straight pipes are eliminated from the fluid simulation, only access pipes and junctions are relevant tick to tick. The number of straight pipes between junctions or access points is only counted once and is simulated as flowing at uniform speed with a linear pressure gradient from end to end.
One difficulty would be visuals and destruction. How do you show the fluid type, flow direction and speed if the pipe is under ground? How do you select it to show the pipes details or to destroy the pipe if there is something build on top? I would say that if something is on top of a pipe then the pipe is inaccessible. Destroy the thing on top before you can destroy the pipe. The destruction planer would destroy both for an area effect or just the building on top for single clicks, both for double click. Reverse for undoing a construction plan.
Taking a pipe into the hand could make buildings transparent to show the under ground pipes below. Easier to place a junction in the right place under a building that way.
Extra features:
- Access pipes could support circuits. Read pipe content (pressure) and flow direction (N, S, W, E signals).
- Straight pipes could go under water. And hey, we could have offshore oil platforms. They would have to be near land or within construction robot reach to build but would be neat.
- Straight pipes and junctions could be the same item with some other mechanism to pick how pipes connect.