Who owns the side sewer in King County?
The side sewer is the pipe that carries your house's wastewater out to the public sewer main. In Seattle, and in most of King County, the homeowner owns it, and the ownership runs past the property line all the way to where the pipe connects to the main. That stretch under the sidewalk, the planting strip, and part of the street is yours.
The city or sewer district owns and maintains the main itself. Everything between your foundation and that main is your pipe and your repair bill.
Why this surprises people
Most owners assume the line becomes public at the property line, the way the water meter works. It doesn't. A break under the street in front of your house is still your break. That's why a sewer repair that crosses the sidewalk can run into real money: the work may involve a side sewer permit, traffic control, and street restoration, all on top of the pipe itself.
How you find out where the problem is
You can't tell from the surface. The tool that answers it is a sewer camera scope. A plumber feeds a camera down the line from a cleanout and records the pipe's condition end to end. The scope shows whether the trouble is root intrusion, a separated joint, a belly, or a collapse, and roughly how far out it sits.
A scope is also what a home inspector orders during a sale in the older neighborhoods. Clay and concrete side sewers under pre-war Seattle houses fail on a schedule, and sellers get asked for the footage.
What to do with the scope results
- Roots or scale in a sound pipe: cleaning usually buys years. A cutter head clears the intrusion and the pipe stays
- A separated joint or crack on your side: spot repair or lining, depending on how much of the run is bad
- A collapse or a line that's failing end to end: replacement. Trenchless methods pull or burst a new pipe through the old path on many lots, which matters when the lateral runs under landscaping or a driveway
- Damage in the main itself: that's the utility's problem. The scope footage is what you show them
If you're staring at a backup and don't know which side the break is on, describe what happened in the request and say whether neighbors have the same problem. A shared backup usually means the main; a backup at one house usually means the lateral.
