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Utility marking colors follow a national standard set by the American Public Works Association (APWA): white for proposed excavation, pink for temporary survey, red for electric, orange for telecom, yellow for gas, green for sewer, blue for water, and purple for reclaimed water. But understanding the colors is only part of safe excavation planning. Calling 811 only marks public utility lines. Private lines on your property are not covered, and that gap is where most utility strikes occur.
Markings like these are everywhere, especially around new construction. Construction crews nationwide mark the ground to represent underground infrastructure like water lines, sewer and drain lines, and gas and electric lines. Each variation 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.
At GPRS, (Ground Penetrating Radar Systems), the nation’s largest private utility locating company, 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.
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 Color Codes for Temporary Marking of Underground Facilities (ANSI/APWA Standard)” 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.
APWA Utility Marking Color Codes: Frequently Asked Questions
To answer any questions, you may have about what each utility color marking represents, you can review the FAQ below:
What does white spray paint or white flags mean on the ground?
White markings indicate proposed excavation limits or routes. They are placed by the excavator to show where digging is planned, so utility companies know which area to locate and mark.
What does pink spray paint or pink flags mean on the ground?
Pink markings indicate temporary survey markings. They are used by surveyors to mark reference points and benchmarks, and are not associated with a specific utility type.
What does red spray paint or red flags mean on the ground?
Red markings indicate electric power lines, cables, conduit, and lighting cables. This includes high-voltage transmission lines as well as lower-voltage distribution lines.
What does orange spray paint or orange flags mean on the ground?
Orange markings indicate telecommunication lines, including telephone, cable TV, fiber optic, and alarm or signal lines.
What does yellow spray paint or yellow flags mean on the ground?
Yellow markings indicate natural gas, oil, steam, petroleum, or other gaseous or flammable materials. Yellow is one of the most critical markings on a job site given the explosion and fire risk associated with these utilities.
What does green spray paint or green flags mean on the ground?
Green markings indicate sanitary sewer and drain lines, including storm sewers and drainage systems.
What does blue spray paint or blue flags mean on the ground?
Blue markings indicate potable water lines. These are the lines that supply drinking water to homes, businesses, and fire hydrants.
What does purple spray paint or purple flags mean on the ground?
Purple markings indicate reclaimed water, irrigation, and slurry lines. These are non-potable water systems typically used for landscaping or industrial processes.
Why 811 Alone Isn’t Enough: The Private Utility Problem
811 One Call is an essential first step before any excavation on public property, but it has a significant limitation: it only covers public utility lines. Private utility lines on commercial properties, campuses, industrial facilities, and residential properties are not mapped or marked through the 811 system. That gap is where utility strikes happen.
Private utility locating by a qualified provider is the only way to identify lines that 811 doesn’t cover. GPRS Project Managers use GPR and EM locating technology, governed by the Subsurface Investigation Methodology (SIM) standard, to locate and mark both public and private utilities on your job site using utility locate color codes that conform to the APWA standard. Since 2017, GPRS has maintained a 99.8% accuracy rate across more than 300,000 projects.
Protect Your Project with Accurate Private Utility Locating
GPRS (Ground Penetrating Radar Systems) follows APWA nationwide guidelines to keep your job site on budget, on time, and safe. Understanding what utility marking colors mean is the starting point. Knowing that your private lines are accurately located and mapped is what actually prevents strikes. Contact GPRS to schedule a private utility locate, or visit our utility locating services page to learn more.
