A PFD (Process Flow Diagram) describes the basic flow through a system. This is a generalised document.
A P & ID (Sometimes called either a Piping and Instrumentation Diagram, or a Process and Instrumentation Diagram) illustrates all details related to the control of flow through the system...
I am trying to find a table to correlate gravity flow in drainage piping with pipe bore (used to have one, but lost it!) . Also, is there any data on gravity flow and angle of incline of drainage piping??