Pipe Drawings are much different from specific weld symbols but they do have a similar relationship from part to symbol. Some individuals will not see these in their line of work but it is important to be aware of them.
As with weld symbols, pipe symbols are a reflection of what that part would look like in theory. For example if a 90 degree elbow is to be placed in service the drawing will reflect a 90 degree angle. There may be multiple symbols for one fitting or part depending on the fashion it is to be installed (Butt weld, Socket Weld, Threaded.)
Below is a breakdown of almost every type of fitting and connection.
Coordination System Symbols for Isometrics
Note: Symbols are shown in black lines. Lighter lines show connected pipe, and are not parts of the symbols.