Buying a House in Snohomish or King County: Sewer Scopes and Who Owns the Side Sewer (2026)

Short answer: The pipe that carries wastewater from a house to the public sewer is called the side sewer, and in most of Snohomish and King County the homeowner owns it. A standard home inspection doesn’t look inside it, because Washington’s inspector rules exclude underground items. A sewer scope runs a camera through the line so you can see roots, cracks, sags and offset joints before you’re the one paying to fix them. Book it inside your inspection period and read the video with someone who knows what they’re looking at.

This is general information, not legal, plumbing or insurance advice. Each city and sewer district sets its own ownership line and permit rules, so confirm with the utility that serves the house.

Why a standard inspection doesn’t cover it

Washington licenses home inspectors and sets their standards of practice in WAC 308-408C. Under WAC 308-408C-030, an inspector isn’t required to "determine the existence of or inspect any underground items." The plumbing section, WAC 308-408C-100, covers visible water supply lines, visible waste and vent lines, fixtures and the water heater. The inspector runs fixtures and checks that they drain, but isn’t required to inspect plumbing that isn’t readily accessible. So a house can pass the drain test on inspection day and still have a cracked or root-filled line under the yard.

That’s what a sewer scope is for. A contractor feeds a camera through a cleanout or other access point and records the inside of the pipe. Our guide to what a standard home inspection covers explains what the rest of the inspection covers. If the house uses a septic system instead of public sewer, that’s a different inspection entirely.

Who owns which part of the pipe

The side sewer runs from the house to the public sewer main. Where the owner’s responsibility ends depends on the city or district. Here’s how three local utilities describe it on their own pages.

‍

‍

Based on: Seattle Public Utilities, Your Side Sewer and Side Sewer Permits pages; City of Kirkland, Wastewater page; City of Lynnwood, Sewer Line Cleaning page.

Lynnwood’s page adds a detail buyers should know: if the owner can’t clear a blockage in the service lateral, the owner first hires a professional, and the city responds only if there’s an accessible cleanout at the property line. If there isn’t one, the city requires the owner to install it first. And if the blockage turns out to be roots or buildup in a structurally sound pipe, the city charges the owner for the cleaning. If the house is served by a different city or a sewer district, ask that utility where its line is drawn.

Kirkland says it has 11,202 private side sewer connections to its mains and may have an as-built record showing where a given side sewer runs. You can ask Kirkland Public Works at 425-587-3800. Seattle Public Utilities can help you find a side sewer on its mapping system and check whether it has an inspection video of the connection; its contact is SideSewerRequests@seattle.gov.

What the camera can find

Seattle Public Utilities publishes a plain-language guide to side sewer defects and how serious each one is. It’s a useful yardstick when you’re watching a scope video, wherever the house is.

‍

Based on: Seattle Public Utilities, Side Sewer Defects & Issues page.

SPU says owners are responsible for removing roots up to and within the connection to the main, and that removing trees near a side sewer probably won’t fix a root problem, since roots can grow up to twice a tree’s height. Repairs need a permit: in Seattle, SPU’s permit page says a side sewer permit is required to construct, repair or alter a side sewer, on private property or in the public right-of-way. SPU recommends getting at least three bids before repair work starts.

Fitting it into your purchase

• Read the seller disclosure. Form 17 asks whether the house is on public sewer or an on-site system (Item 3A), whether the house is connected to the main if public sewer is available (3B), whether there are sewage fees beyond the regular bill (3C), and whether all plumbing fixtures, including the laundry drain, are connected (3E). RCW 64.06.020 currently has two versions on the Legislature’s site: one marked effective until January 1, 2027, and one effective January 1, 2027. The questions quoted here appear in both. If your sale runs across the new year, check which form is being used.
• Schedule the scope early. Your inspection deadline is set by your purchase agreement; see our guide to contingencies. A scope that finds a problem on the last day leaves little time to get a repair bid.
• Ask about shared lines. If the pipe joins a neighbor’s line before the main, SPU says the owners share responsibility from where the pipes meet. Any easement for a shared side sewer is tied to the property titles. Your preliminary title commitment will list recorded easements.
• Ask your insurance agent. Washington’s Office of the Insurance Commissioner lists sewer backup and sump pump overflow as an optional endorsement. Its homeowner guide says that coverage applies if the sewer line backs up because of an issue off your property, and that a homeowner policy won’t cover flooding.

If the scope turns up work that was done without permits, our guide to unpermitted work covers how that’s handled in a sale.

FAQ

Does a home inspection include the sewer line?

Not the buried part. Washington’s home inspector standards say inspectors aren’t required to inspect underground items (WAC 308-408C-030), and the plumbing standard covers visible drain and waste lines plus a check that fixtures drain (WAC 308-408C-100). A sewer scope, where a camera is run through the side sewer, is a separate service you usually book on your own.

Who pays to fix a broken side sewer after I buy?

Usually you do. In Seattle and Kirkland the owner owns the whole side sewer out to the public main, including the part under the street. In Lynnwood the owner maintains the side sewer to the edge of the right-of-way or easement and cleans the service lateral, and the city repairs structural problems in the lateral. Other cities and sewer districts set their own lines, so ask the utility that serves the house.

What if the sewer scope finds a problem during my inspection period?

That depends on your purchase agreement and inspection contingency. Common options are asking the seller to repair, asking for a price change or credit, or ending the deal within the contingency deadline. Get a written repair estimate so you’re negotiating over a real number, not a guess.

What is a shared side sewer?

It’s when the pipe from your house joins a neighbor’s pipe before it reaches the public main. Seattle Public Utilities says the owners share maintenance and repair responsibility from the point where the pipes join, and that an easement recorded when the line was built stays with the properties after they sell. Ask title for any recorded easement.

Does homeowners insurance cover a sewer backup?

Not automatically. Washington’s Office of the Insurance Commissioner lists sewer backup and sump pump overflow as an optional endorsement you may want to ask about, and its guide says a standard homeowner policy doesn’t cover flooding. Ask your insurance agent what the policy covers before you close.

Talk it through with a local agent

Peter Kim and Odigo Real Estate Club can help you fit a sewer scope into your inspection period and work out what to ask the seller for if it finds something, with 25+ years combined experience, 593+ closings, and 122 five-star Zillow reviews. See our home buying services.

Odigo Real Estate Club · REAL Brokerage, WA #112064 · 16108 Ash Way, Suite 201, Lynnwood, WA 98087 · (425) 409-3823 · Mon–Sat 9 AM–6 PM, closed Sunday

Sources

• Washington State Legislature, WAC 308-408C-030 (home inspector exclusions; not required to determine the existence of or inspect underground items), https://app.leg.wa.gov/wac/default.aspx?cite=308-408C-030 , accessed Nov 3, 2026.
• Washington State Legislature, WAC 308-408C-100 (home inspection of the plumbing system; visible lines, functional drainage, items not required), https://app.leg.wa.gov/wac/default.aspx?cite=308-408C-100 , accessed Nov 3, 2026.
• Seattle Public Utilities, Your Side Sewer (owner owns the side sewer to the public main; shared side sewers; SideSewerRequests@seattle.gov), https://www.seattle.gov/utilities/your-services/sewer-and-drainage/side-sewers , accessed Nov 3, 2026.
• Seattle Public Utilities, Side Sewer Defects & Issues (offset joints, sags, cracks, debris, roots; easements; three bids), https://www.seattle.gov/utilities/your-services/sewer-and-drainage/side-sewers/defects-and-issues , accessed Nov 3, 2026.
• Seattle Public Utilities, Side Sewer Permits (boundaries of the side sewer; permit required to connect, construct, repair or alter a side sewer), https://www.seattle.gov/utilities/construction-resources/sewer-and-drainage/side-sewer-permits , accessed Nov 3, 2026.
• City of Kirkland, Wastewater (public and private responsibility; 123 miles of mains; 11,202 private side sewer connections; as-built records, 425-587-3800), https://www.kirklandwa.gov/Government/Departments/Public-Works-Department/Wastewater , accessed Nov 3, 2026.
• City of Lynnwood, Sewer Line Cleaning (owner and city responsibilities; side sewer, service lateral and cleanout definitions), https://www.lynnwoodwa.gov/Government/Departments/Public-Works/Sewer-and-Water-Utilities/Sewer-Line-Cleaning , accessed Nov 3, 2026.
• Washington State Legislature, RCW 64.06.020 (seller disclosure statement form; version effective until Jan 1, 2027 and version effective Jan 1, 2027), https://app.leg.wa.gov/RCW/default.aspx?cite=64.06.020 , accessed Nov 3, 2026.
• Washington State Office of the Insurance Commissioner, Learn how home insurance works (optional endorsements, including sewer backup and sump pump overflow), https://www.insurance.wa.gov/insurance-resources/home-insurance/how-home-insurance-works/learn-how-home-insurance-works , accessed Nov 3, 2026.
• Washington State Office of the Insurance Commissioner, A consumer’s guide to: Homeowner Insurance (PDF) (sewer backup or sump pump overflow endorsement; flood not covered by a homeowner policy), https://www.insurance.wa.gov/sites/default/files/2025-03/homeowner-insurance-guide.pdf , accessed Nov 3, 2026.

‍