Usually if you were to scale anything for accuracy, you would go to the architectuals. The plumbing drawings, although still drawn to whatever scale is dictated, will not show dimensions. That would mean if you had scaled it without a given dimension and it were scaled at, say 1/8 inch = a foot, you could be off by enough to have your pipe in the hallway instead of the in the wall. Another example of why plumbers will look into each section of the drawings in order to correctly install.

What year apprentice?

I'll see what I can do.

The designer of the drawing will always utilize different symbols for different things. These symbols and abbreviations will be noted on the first page of the drawings. In this case the designer used that symbol for a shower.