What Do the Utility Marking Colors Mean?

What Do the Utility Marking Colors Mean?

Markings like these are everywhere, especially around new construction. What do these flags and spray-painted markings mean?

Utility Flag and Marking colors displayed
Utility Marking Colors Displayed

If you are wondering the answer to these questions, then you’re in the right place. Construction crews nationwide mark the ground to represent underground infrastructure like water lines, sewer and drain lines, and gas, and electric lines. Each one of these variations of subsurface infrastructure is represented by a different colored marking. 


Appropriate colors should be used to mark utilities when possible. The 811 One Call hotline system in each state has implemented specific color codes for marking all utility locates nationwide. Calling before you dig is the law, and if these markings are on public property you plan to dig on, then you’ve made a wise decision to look up what each color marking means. While calling your local hotline affiliate is the law, 811 One Call’s locating is limited to mapping out public utility lines, not private.


Different Utility Color Flags Displayed From a Utility Locate

At GPRS, we perform subsurface utility locating using ground penetrating radar (GPR) technology, Video (CCTV) Pipe Inspection, and concrete imaging/scanning, providing peace of mind through confirming the location of public utilities, as well as locating lines on private property.

Underground utility lines can lie at different depths depending on where you are in the U.S. with a variation that ranges from 2 to 3 feet deep, or more. This is important to know because when you call before you dig you should not expect to have the depth of utility’s located to be provided.  

At GPRS however, we use multiple forms of technology including Ground Penetrating Radar (GPR) and Electromagnetic (EM) Utility Locators, adhering to the industry’s leading utility locating practice, and Subsurface Investigative Methodology (SIM), to pinpoint underground utilities accurately, while also providing depths of utility’s located, where applicable.

Once your lines are located before digging or breaking ground, and accurately mapped for both private and public utilities on site, you will see utility markings with color-coded flags and or spray-painted lines and abbreviations that are used to mark the location of utilities. The lines signify not only the perimeter of an area under inspection, but also the direct location of the underground utility lines on site. It is up to you to respect local and national regulation regarding distance that must be maintained from utility markings when digging or construction occurs. By knowing the assigned colors, you can be proactive and aware of the types of utilities buried below, ensuring that lines and pipes remain undamaged.  Call before you dig guidelines shares national recognized color codes for differing underground utilities as created and mandated by the American Public Works Association (APWA):


What is the APWA?

The American Public Works Association, (APWA) is the voice for public works, and also for the private sectors who provide products and services to those in public works. The APWA is a useful resource for many, and they put into place the national guidelines for color marking when performing utility locating on private or public property. 

The APWA’s “Uniform Temporary Marking of Underground Facilities” recommends the specific color code that should be used to mark the location of underground facilities, temporary survey markings, and intended excavation sites. When a utility company marks a location, they are advised to include a color code that consists of White, Pink, Blue, Green, Yellow, Orange, Red, and Purple color markings of both flags and spray paint to represent what each of lines located represent. 

At GPRS, our nationwide network of Project Mangers follows the APWA’s standard to ensure our partners in safety know what they are looking at when observing our markings and our utility mapping data is stored within SiteMap® to help keep private and public workers safe. To answer any questions, you may have about what each utility color marking represents, you can review the FAQ below:


Yellow Flag

What does a yellow utility flagstand for?

A yellow utility flag stands for natural gas and oil, steam, petroleum, or other gaseous or flammable materials.

Red Flag

What does a red utility flag stand for?

A red utility flag stands for electric power lines, cables, or conduit, and lighting cables.

Orange Flag

What does an orange utility flag stand for?

An orange utility flag stands for phone and telecommunication lines, alarm or signal lines, cables or conduits, and fiberoptics.

Blue Flag

What does a blue utility flag mean?

A blue utility flag stands for potable (drinking) water.

Green Flag

What does a green utility flag mean?

A green utility flag stands for storm and sanitary sewers, drainage facilities,or other drain lines.

Purple Flag

What does a purple utility line stand for?

A purple utility flag stands for reclaimed water, irrigation, and slurry lines

White Flag

What does a white utility flag mean?

A white utility flag means pre-marking of the outer limits of the proposed excavation or marking the centerline and width of proposed lineal installations of buried facilities.(proposed excavation limits or route)

Pink Flag

What does a pink utility flag mean?

Pink utility flags are for temporary survey markings, unknown / unidentified facilities

GPRS follows these nationwide guidelines so that we keep your job site on budget, on time, and safe, protecting you from the dangers of subsurface utility strikes. To learn more about how you can better protect yourself and your job site from the dangers of utility strikes, through the use of an accurate private utility locating company near you, click here: https://www.gp-radar.com/services/utility-locating-services

Private vs. Public Utility color Flags and markings explained
Private vs. public utility lines with color markings explained.