Side Sewer Maintenance

Rendering of side sewer damage
Graphic shows sewer line responsibility, which extends to the sewer mainline.

Side Sewer Maintenance

A "side sewer" carries wastewater from a building's sinks, toilets and drains to the public sewer. Side sewers are sometimes called "sewer laterals" or just "sewer pipe."


If you own your home or building, you own your side sewer until it connects to the public sewer pipe. Some properties share a side sewer.

Maintenance Steps

1. Know where it is: download your property’s side sewer information from the Seattle Department of Construction and Inspections (DCI) website.

2. Take care of it: flush only toilet paper and properly dispose of grease.  Learn more about what happens to sewer pipes when we flush items other than toilet paper. 
3. Get it inspected

  • Hire a plumber or sewer inspector who can run a video camera through your side sewer to find problems.
  • Learn about typical side sewer problems (common issues and defects).
  • Choose a sewer inspection company, plumber, or side sewer contractor to inspect your side sewer. 
  • Remember! Have the side sewer inspected before you purchase a property.

4. If needed, clean or repair it

  • Regular cleaning can prevent costly repairs, and broken side sewers must be fixed.
  • Hire a contractor to clean or repair your side sewer. 
  • Learn more about side sewer repair methods.

Backwater valve ownership

Some Seattle properties may have backwater valves installed to help prevent sewer backups. If you have one of these valves, you are responsible for its maintenance. For more information on how to take care of your backwater valve, consult the manufacturer's web site or other maintenance resource.