Sewer backups may be caused by utility lines that intersect sewer lines. These intersecting lines are known as “cross bores.”

A plumber who attempts to clear this type of blockage may damage the utility line that was bored through the sewer line. If an electric line is cut, the plumber is at risk for electrocution. If a gas line is damaged, gas can migrate through the sewer line into homes and buildings, which could result in a major fire or explosion.

If your work involves cleaning out a sewer line that is blocked between the house and sewer main, take these precautions:

  • Contact MISS DIG 811 by calling 811 or by going to Request an emergency staking request due to sewer blockage in order to have utility lines located and marked that might cross the path of the sewer line.
  • Use a camera to identify the location of the blockage. If the evidence of recent excavation or utility marks are the same distance from the building as the blockage, a cross bore may be the cause.
  • If you suspect or determine the blockage is caused by a cross bore, do not attempt to clear the blockage. Instead, get help from the utility owner that may be involved.


Cross bores occur when an excavator unknowingly bores a utility line through a sewer lateral.


Be Alert For Cross Bores