What These Spray Paint Spots Really Mean on the Street [update]
Walking through the city, you may have noticed traces of spray paint on the streets and sidewalks. It is clear that they are here to mark something, but what? It turns out that builders don’t just paint for fun – these markings are designed to protect you.
The main purpose of markings on a street or sidewalk is to indicate where pipes, air ducts, cables and other structures are located and in which direction they flow, so as not to damage them or destroy them during construction. If you’ve ever seen a water (or worse, a sewer) pipe break through, you know how bad it can be for you and everyone else trying to get through the area (and of course, it’s terrible for the builders ). In addition to this inconvenience, a cut in a service line can disrupt access to water, electricity, and other utilities for your home or work.
In addition to helping builders maintain the integrity of underground structures, your city may also use spray paint markers to track services performed, such as the one San Francisco uses to confirm that a sewer has been treated with methoprene (which prevents mosquitoes in wastewater ). …
Update 5/5/2017 10:53 AM: In response to our discerning commenters, we’ve added information about the 811 program and what the marking colors mean.
Builders and city services aren’t the only ones using these markings – you may have asked your city to mark pipes and cables on their property before digging up the tree stump or making other changes. This service is known as 811, and the American Public Works Association worked with them to decide what certain colors meant. Here are the ones for my local service 811 (you probably have the same).