The American Public Works Association (APWA) has developed a color code for marking underground utilities across the United States. This standard keeps us all on the same page and makes the world we live and work in a little bit safer for everyone.
The most common colors people might encounter are orange, red, yellow, and blue.
Orange
Orange painted lines on the ground represent communications lines such as fiber optic telephone or broadband internet cables, but can also include cables carrying traffic, railroad, or other signaling information as well.
Red
Red paint indicates the presence of underground electrical wires. A red mark on the ground can represent electrical power ranging from low-voltage decorative lighting to high-voltage distribution systems. You should always use extreme caution around any facilities painted or flagged.
Yellow
The color yellow is used to designate petroleum products, in either liquid or gaseous form, as well as pressurized steam pipelines. Natural gas and propane are probably the two most common gases found in residential and commercial settings today. Cross-country petroleum transmission pipelines are also usually marked in this color. It is a felony to deface temporary or permanent pipeline markings.
Blue
Potable or drinking water is marked with blue paint or flags. This includes the water mains delivering municipal water to your home or business as well as water from wells used for human consumption.
Purple
Purple marks mean the water in the pipe below has been reclaimed and is unfiltered and unfit for human consumption. Reclaimed water is sometimes used for irrigation purposes.
Green
Green paint indicates the presence of underground sewage pipelines Some sewage systems include pressurized pipes called forced mains. These systems depend on mechanical pressure to move wastewater from one place to another, rather than relying on gravity to get the job done. You do not want to be present if a forced sewer main is ruptured.
The final three elements of the APWA color code are pink, purple, and white. White paint should be reserved only for marking proposed excavation routes or areas.
Pink
Pink is used for temporary survey marking and may indicate anything from an underground utility to a surveyor’s benchmark. We often use pink paint to mark utilities I cannot otherwise identify.
Any lines painted or flagged should always be treated as an unknown until you have physically verified the utility or utilities beneath. Professional locators do their best to provide accurate surface information to excavators and others who utilize our work, but I’d rather mislabel a facility than leave it unmarked. For more information, please visit the American Public Works Association or Common Ground Alliance.