Before you dig, excavate, or even pound a fence post, calling 811 gets your utility lines marked—free in all 50 states. But knowing exactly what a standard mark-out includes can save you from costly delays, damaged pipes, and serious safety hazards. Here's what to expect when you request 811 services and what gets marked (and what doesn't).
What 811 Services Actually Cover
When you dial 811 or submit a locate request online, you're triggering a notification system that alerts utility companies in your area. The locating companies then send crews to physically mark underground infrastructure on or near your property.
A standard mark-out typically covers the major utilities that run beneath most residential and commercial properties:
- Natural gas lines (usually marked in yellow)
- Electric lines (typically red)
- Telephone and cable lines (white and pink respectively)
- Water mains (blue)
- Sewer and drain lines (green)
- Irrigation and reclaimed water lines (purple or light blue)
Each utility uses its own color code, which makes it easy to see which line is which once they're marked. Most 811 services will mark everything they have records for that crosses your dig site.
The Timeline You Should Expect
Standard mark-outs take time—but not as much as you might think. When you submit a request, most states mandate that utilities respond within 48 to 72 business hours. In competitive urban markets, you might see crews within 24 hours.
This means planning ahead is essential. If you're scheduling a fence installation or foundation work, call at least three business days before your contractor arrives. For smaller projects like planting trees or installing a mailbox, two days usually suffices.
Weekend and holiday requests may take longer since not all utility crews operate on those days. Always verify completion of the mark-out before any digging begins.
What's Typically Not Included
The mark-out marks public utility lines that utility companies maintain. What falls outside standard coverage includes:
- Private property service lines beyond the meter or main connection
- Septic systems on individual properties
- Propane tanks and underground storage
- Fiber optic cables (sometimes, depending on your provider)
- Abandoned or decommissioned lines that may not be in active utility company records
If you have known private utilities—like a septic system or a private well—you'll need to identify and mark those yourself or hire a private locating service. These typically run $150 to $400 depending on complexity and location.
How Accurate Are the Marks?
Utility locators use a combination of ground-penetrating radar (GPR), electromagnetic locators, and historical records to pinpoint lines. Most marks are accurate to within 24 inches horizontally, though some utilities provide tighter tolerances.
Always assume marks have a margin of error. Never dig directly on a marked line—stay several feet away, especially with high-voltage electric or high-pressure gas lines. If you're doing precision work (like trenching for a new waterline), hire a private locating company to get sub-inch accuracy. Expect to pay $200 to $600 for premium private locates.
Comparing 811 Providers and Services
If you're hiring a contractor for excavation work, they typically handle the 811 call themselves. However, if you're managing a DIY project or coordinating multiple trades, you'll interact with 811 directly.
Quality can vary by region. Some areas have dedicated, responsive locating crews; others bundle the service with one utility company that may take the full 72 hours. You can compare 811 service providers and find trusted locating contractors in your area through platforms like Mercoly, which helps you evaluate response times, accuracy ratings, and customer experiences all in one place.
Before hiring any contractor for digging work, ask about their 811 mark-out process. Professionals should never break ground without it.
Frequently Asked Questions
Q: Does 811 mark everything underground on my property? No—811 marks public utility lines. Private systems like septic tanks, well lines, or propane tanks are your responsibility. Check property records and ask neighbors if you're unsure what's on your land.
Q: Can I dig if it rains and the marks wash away? Call 811 again for a re-mark if weather obscures the lines. The service is free, and it's far cheaper than hitting a live cable or gas line.
Q: How long do the paint marks stay visible? Marks typically remain visible for 30 days. If you need to wait longer before digging, request a fresh mark-out a few days before work begins.
Find verified 811 service providers and utility locating contractors near you to ensure your next project stays safe and on schedule.