Utility flags are used to mark underground utility lines like gas, electricity, water, sewer, telecommunications, and cable TV. Knowing what the different colors represent can help identify what type of utility lines are buried where flags are placed. Utility flags help construction crews, landscapers, and homeowners avoid accidentally digging into and damaging underground lines which can be dangerous, disrupt service, and lead to costly repairs.
Why are utility flags used?
Utility flags are an important visual marker used to indicate the location and path of buried utility lines. They provide a warning to those digging or excavating to be cautious and avoid underground infrastructure when working in the area. Without utility flags marking their position, underground lines would be invisible and more prone to accidental damage and disruption of service. Recognizing the colors and patterns of utility flags allows people to work safely around buried utilities.
When are utility flags required?
In most areas, laws require anyone excavating or disturbing the soil to call 811 before starting work. This “Call Before You Dig” number contacts the local utility locator service who will dispatch crews from appropriate utility companies to visit the site and mark their buried lines with flags. This utility locating service is free as the purpose is to prevent accidents and damage. Laws typically require flags to be placed at least 2-3 business days before excavation work begins. Flags must remain visible throughout the project.
Who places the utility flags?
Trained utility locators are responsible for placing the correct colored flags to mark their company’s underground infrastructure. After a request is made to 811, locators from utility companies like gas, electric, cable TV, etc. will visit the site to review maps and use specialized equipment to detect and trace their buried lines. They paint lines on the ground and place colored flags to clearly mark the position of underground utilities.
How are utility flags placed?
Locators mark underground lines by painting colored stripes on the ground aligned with the position of buried utilities detected during scanning. Flags matching the paint color are placed along the stripes to make the markings more visible. In some cases, just paint or just flags may be used. Flags are typically placed every 4 to 10 feet depending on site conditions and the complexity of utilities present. Additional symbols and text may be painted on the ground providing details about the utility.
What do the utility flag colors mean?
Utility companies use standard colors on flags to identify their type of underground infrastructure. The American Public Works Association (APWA) standard color code is:
| White | Proposed Excavation |
| Pink | Temporary Survey Markings |
| Red | Electric Power Lines, Cables, Conduit and Lighting Cables |
| Yellow | Gas, Oil, Steam, Petroleum or Gaseous Materials |
| Orange | Communication, Alarm or Signal Lines, Cables or Conduit |
| Blue | Potable Water |
| Purple | Reclaimed Water, Irrigation and Slurry Lines |
| Green | Sewers and Drain Lines |
Additional colors may be used in some areas so check with your local utilities if you notice a color not listed here.
White Flags
White flags indicate the proposed path of planned excavation or digging. They delineate the boundaries of the work site and provide another visual reference to avoid for utility locators.
Pink Flags
Pink flags are used as temporary survey markings placed by survey crews. They may indicate property boundaries, targets, benchmarks, and other survey data points. Pink does not indicate any underground utilities are present.
Red Flags
Red flags mark buried electrical lines including power transmission, distribution, and service lines. Overhead electric lines and associated guy wires/anchors may also be marked in red. Red indicates caution is needed around electric utilities which can pose electrocution hazards.
Yellow Flags
Yellow indicates the presence of buried gas, oil, petroleum, or other hazardous liquid and gas transmission lines. This includes pipelines transporting materials like natural gas, propane, oil, diesel, fuel, steam, and petrochemicals. Yellow flags are a critical utility marking and require special care to avoid sparks or other ignition sources.
Orange Flags
Orange flags alert crews of buried communication, cable TV, alarm system, and other signal carrying lines. Fiber optic cable, copper telephone wires, coaxial TV cables, and network lines are marked with orange. An orange line is often placed as a warning along the buried utilities trench where various communications lines are present.
Blue Flags
Blue indicates buried drinking water supply lines including water mains and service lines delivering water to homes and buildings. Blue marks pressurized potable water pipes that require avoidance to prevent leaks, water service disruption, and potential contamination.
Purple Flags
Purple flags mark non-potable water lines including reclaimed/recycled water, irrigation, and slurry systems. These lines carry non-drinking water sources to be used for things like agricultural irrigation, industrial processes, dust control, wastewater pipes, etc. Damaging these can impact the environment and project site conditions.
Green Flags
Green flags indicate the position of underground sewer pipes including sanitary sewer lines, storm drains, and drainage systems. Hitting sewer lines can lead to uncontrolled sewage discharges creating health hazards and environmental harm. Green warns to avoid these gravity fed drain lines.
What symbols and codes are used on utility flags?
In addition to colored flags, locators may paint large colored lines on the ground aligned with buried utilities. These markings often include additional symbols, letters, and codes providing more details about the type of utility present:
- Three lines painted together indicates a buried electric line up to 350 kV. Six lines indicate electric 351 kV to 500 kV. More lines are added for even higher voltages.
- Telecom and cable TV lines may show Mary, Internet, Phone, CATV symbols.
- Size of pipe may be shown – 6″ PVC, or distance to the utility – Gas 4′.
- Codes like E (electric), G (gas), T (telecom) may be added.
- Duct banks with multiple conduits are marked with an X over colored lines.
- Arrows indicate direction a line turns at bends.
What if I don’t see any utility flags?
If you plan to dig or disturb the soil, you are required to call 811 at least 2-3 days prior to allow utilities time to visit and mark their underground facilities. If you begin excavating without calling 811 or seeing any utility flags, you could hit an unmarked line. This dangerous and illegal “digging blind” can lead to injuries, utility service outages, environmental incidents, and significant repair costs. When in doubt, take the cautious approach and call 811 before any soil disturbing activity.
Conclusion
Recognizing the meaning of colored utility flags is a critical safety skill for construction crews, excavators, landscapers, and DIY homeowners. Taking the time to call 811 before any digging project will get professional utility locators to visit and mark buried lines with standard colored flags indicating the type of underground infrastructure present. Understanding this color code allows people to work safely around hidden utilities and avoid damaging critical gas, electric, telecommunications, water, and sewer lines. Heeding the warnings of utility flags protects workers, communities, and the environment from preventable underground utility line hits.
