Maybe you’ve noticed paint marks sprayed on pavement. If it’s not a style of graffiti chances are you’re looking at code for a buried utility line.
Depending on the colour paint, the unseen conduit could be carrying sewage or drinking water. How do you know which? Well, it turns out, excavators know which lines lay beneath. There’s an international colour code for utility markings. (ANSI Standard Z53.1) Learning industry codes, parts and processes makes for another interesting day in the field of tech writing.