"What’s the purpose of this component, mounted on the main water line of a house, after the water meter?"
A: "It’s a pressure regulator. It’s a valve that reduces the water pressure, so you don’t get full mains pressure out of your taps."
"They're oil absorbing pads and since oil floats on water the tube is there to stop the oil from flowing while letting the water pass under it"
I had to visit reddit to look it up... I feel dirty.