Sewer Line Safety

Sewer Line Safety

Blocked Sewer Line?  Possible Cross Bore!


If you suspect you have a blocked sewer line, the first thing you should do is call a professional plumber so that the blockage can be cleared properly.  This may involve digging in your yard, and if so, you should call 811 so that utility lines can be marked before any work begins on the sewer line.  Calling 811 is not only the safe thing to do – IT’S FREE AND IT’S THE LAW!  Calling 811 helps determine in advance if the problem could be caused by something called a “cross bore”. 

What is a cross-bore?

Many utilities use “trenchless technology” construction methods to install underground lines. These pipelines and cables may be installed via directional boring, a technique that is an alternative to open trenching and helps to reduce damage to streets, sidewalks, driveways and landscapes, and minimizes restoration costs and reduces road closures.   

While rare, in some cases an underground utility line is unknowingly installed through an existing utility or underground structure, such as a sewer line.  This is known as a "cross bore.”  Cross bores can lay dormant for months or even years, their exact locations unknown.  Often, the first sign of a cross bore is a sewer blockage that may cause the back-up of wastewater in the home or yard. 

When a sewer back-up occurs plumbers typically attempt to clear the blockage with a mechanical rotary device, risking damage to a live utility line.  If that line is natural gas, service interruption may not be immediately obvious.  Leaking gas may travel into sewer lines and neighboring buildings, including one without natural gas, causing a fire and explosion risk. 

Important Safety Tips

  • Call 811 before you clear.
  • Become familiar with the color coding of utility markings.
  • If the markings from existing underground utility lines cross the path of the sewer line, it may be a cross-bore that is causing the blockage.
  • Be alert to any unusual conditions, including:
    • Hissing sounds
    • Natural gas odor (rotten egg smell)
    • Blowing dirt
    • Bubbling water (in a sink, toilet, or other area where water collects)
  • If you reasonably suspect or determine the blockage is caused by a cross-bore:
    • Do not attempt to clear the blockage with a mechanical device.
    • Contact and get help from the utility provider(s) that may be involved.
    • Hand dig in the area where the blockage or the cross-bore may exist.
  • If a cross-bore is discovered:
    • Stop all work.
    • From a safe place, contact the utility operator involved if not already on site.
  • If you suspect a natural gas leak by smelling, seeing or hearing gas escaping:
    • Leave the area immediately, and warn others to leave or stay away from the area.
    • From a safe place, call 911 and contact the gas company for the area.
    • Remain outside until the gas company can send someone to inspect the area.
    • Do not operate electrical equipment or anything or anything that could cause a spark, including phones, lights, appliances, doorbells, flashlights, tools, etc.
    • Do not try to find the leak yourself or operate any pipeline valves.
    • Do not proceed with your work until the utility informs you it is safe to do so.