Private Utility Locating & Ground-Penetrating Radar
Calling 811 gets public utility lines marked, but usually only up to the meter or property line. Lines owned by the property owner, like power to a garage, gas to a pool heater or a sewer lateral, are often not marked at all. Private locators fill that gap.
- Construction
- Landscaping
- Homeowners
Photo: private locator pushing a ground-penetrating radar cart across a parking lot and marking findings with paint
Lines 811 often doesn’t mark
- Electric lines from the meter to garages, barns, pools, lights and signs
- Gas lines after the meter, to grills, pool heaters and outbuildings
- Propane lines from private tanks
- Sewer laterals and septic lines
- Irrigation and water lines on the property
- Campus, plant, hospital and school systems
- Parking lot lighting and gate power
- Abandoned lines that may still be live
How private locators find lines
| Method | Finds | Limits |
|---|---|---|
| Electromagnetic locator | Metal pipes and cables, and lines with tracer wire | Can’t find plastic pipe without tracer wire |
| Ground-penetrating radar (GPR) | Metal and non-metal lines, voids, tanks | Limited in wet clay and salty soils; depth estimates vary |
| Sonde or camera in the pipe | Sewer and drain lines | Needs access to the pipe |
| Records and as-built drawings | Locations where documented | Often outdated or missing |
No method finds everything. Confirm critical lines by potholing with hand tools or vacuum excavation. See Hydro & Vacuum Excavation.
Marking colors
| Color | Utility |
|---|---|
| Red | Electric power |
| Yellow | Gas, oil, steam |
| Orange | Communications, cable, fiber |
| Blue | Drinking water |
| Purple | Reclaimed water, irrigation |
| Green | Sewer and drain |
| Pink | Temporary survey marks |
| White | Proposed excavation |
Ask the owner. Before digging on private property, ask the owner or facility manager about private lines, look for clues like lights, meters, tanks and cleanouts, and hire a private locator when needed. See Call 811.
Standards & references
- 29 CFR 1926.651(b): Locating underground installations
- Call 811
- See also: Utility Strikes
Last updated: