If a sewer main backs up, what will generally happen?

If a sewer main backs up, what will generally happen?

• A. The mainline will backflow
• B. Service lines will fill up
• C. House drains will reverse
• D. Water infiltration occurs

Answer: (B)

When the sewer main backs up, sewage can’t move forward in the main, so the pressure pushes backward into the lines that connect the main to properties. Those service lines are the direct conduits from the main to each home, so wastewater will generally fill up these service lines first. As the backup worsens, it can push into house drains and fixtures, but the immediate and most common effect is the service lines filling with sewage. Water infiltration isn’t tied to a sewer main backing up, and a mainline backflow is just restating the situation rather than describing what the downstream lines do.

When the sewer main backs up, sewage can’t move forward in the main, so the pressure pushes backward into the lines that connect the main to properties. Those service lines are the direct conduits from the main to each home, so wastewater will generally fill up these service lines first. As the backup worsens, it can push into house drains and fixtures, but the immediate and most common effect is the service lines filling with sewage. Water infiltration isn’t tied to a sewer main backing up, and a mainline backflow is just restating the situation rather than describing what the downstream lines do.