The case of a piece that could go missing

Question

What piece of hardware was after all unnecessary? And how?

_{These diagrams, though somewhat schematic, are meant to directly represent everything pertinent. Nothing has been omitted or added to confound or mislead.}

Answer 1

The right half of the assembly on the middle row

because

the combined assembly on the bottom row replaces that part with the assembly from the top row.

Answer 2

You don't need the

choke valve shown in the second row.

This is because

you could turn handle of the switch valve shown on the top row clockwise, choking off the inflow to the junction. The flow will mostly shoot over the lower branch, and any drips that go down the lower branch anyway will be held by the flap covering the lower outlet.