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Utility markings accuracy & Locating Underground Pipes

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How Accurate Are Utility Markings?

Have you ever seen strange markings on the pavement, sidewalk or dirt around a site that is about to be excavated? Sometimes they look like colored lines, while other times you’ll see bright symbols and/or colored flags dotting a property. These are utility markings. They are placed after a utility locator discovers the general location of a utility.

Without these symbols, utility lines and structures could be damaged or destroyed during excavation. Even worse, people could be harmed or killed while working in construction if they do not know where underground utilities are located. But can you always trust utility locator markings to be accurate? Here’s what you should know about these markings and what tools you can use to find underground utility structures yourself.

Person Using Pipe Locator

Utility Marking Accuracy

When utilities are properly located and marked, they can generally be found within two feet of the mark (on either side). This means that as a construction worker or homeowner working on a deep dig project, you should maintain at least a 2-foot berth around all markings. If utility markings are not properly located or if they are somehow damaged or removed, the company or person who placed the markings is responsible to pay for any damage caused by their error.

How Are Utilities Located?

There are a variety of materials used in the manufacturing of underground utility lines, so it can be challenging to locate them all. Different methods must be used for different materials. For example, electromagnetic cable locator equipment is used to locate metal cables and pipes, while ground-penetrating radar or other types of pipe locator radiolocation are required to locate concrete or plastic pipes.

Once located, specific color codes must be used to designate what type of utility lies beneath the mark. In the United States, the following colors are used:

  • Red: lighting cables, electric power lines, conduit
  • Yellow: oil, natural gas, petroleum, steam, other flammable or gaseous material
  • Orange: alarm or signal lines, telecommunication cables or conduit
  • Blue: drinking water
  • Green: Sewers and drain lines
  • Pink: Unknown facilities or temporary survey markings
  • Purple: reclaimed water, slurry lines and irrigation
  • White: proposed excavation routes or limits

These color codes follow the American Public Works Association guidelines.

Pipes located and excavated


Get the Right Tools

Whether you’re a homeowner getting ready to install a sprinkler system or a contractor building a home, you may want to double-check all utility locations to keep yourself and others safe. From pipe locators to cable locators, you can find the tools you need at Engineer Supply.

Browse our inventory of cable & pipe locators or call us at 800-591-8907 to get started.

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