Short definition
A SPU side sewer permit is the authorization issued by Seattle Public Utilities (SPU) for any work connecting, replacing, or repairing a side sewer — the pipe from a building’s foundation to the public sewer main. As of October 1, 2025, SPU (not SDCI) administers side sewer permits in Seattle. A SPU-registered side-sewer contractor must pull and execute the permit; homeowners cannot self-permit side sewer work.
What it is
A side sewer is the pipe that carries waste from a building’s foundation to the public sewer main, typically under the front yard and across the public right-of-way. It’s owned and maintained by the property owner up to the connection at the main.
For decades, side sewer permits in Seattle were issued by SDCI. As of October 1, 2025, side sewer plan review, permitting, and inspection moved to SPU — putting all of Seattle’s water and sewer authority under one utility.
The SPU side sewer permit covers:
- New connections to a public sewer main.
- Side sewer replacement (full or partial).
- Extension or repair of an existing side sewer that crosses public right-of-way.
- Cleanout-to-grade additions that tie into the side sewer.
- Backwater valve installations on side sewers.
Authority basis: Seattle Municipal Code (SMC) Chapter 21.16 governs side sewers, plus SPU Director’s Rules.
The contractor requirement is unique among Seattle plumbing permits: only SPU-registered side-sewer contractors can pull and execute side sewer permits. Homeowners cannot self-permit side sewer work in Seattle. The SPU registration is in addition to standard L&I licensure.
If the work crosses or occupies public right-of-way (street or sidewalk excavation), a separate SDOT (Seattle Department of Transportation) right-of-way permit is also required.
Why it matters to a homeowner
The single most consequential WA-specific permitting nuance for Seattle homeowners.
Side sewer work is expensive. Excavation, public-ROW work, possible main tap-in fees, and SPU permit fees combine into a typical $5,000–$25,000+ project for a side sewer replacement. The permit fee itself is a small fraction (typically $500–$1,200), but the new 2026 drainage System Development Charges (SDCs) added at invoicing have raised total costs.
Contractor selection is constrained. Only SPU-registered side-sewer contractors qualify. The pool is smaller than the general plumbing-contractor pool; getting multiple competitive quotes can take longer.
Pre-purchase inspection scenarios. When a sewer scope at home purchase reveals compromised side sewer (Orangeburg pipe collapsing, root intrusion, sag), the buyer typically negotiates a credit and escrow for the eventual replacement. The contractor selection happens later; the buyer commits to using a SPU-registered contractor.
2026 invoicing changes. Effective January 1, 2026, drainage System Development Charges (SDCs) are added to side sewer permit invoices. As of May 4, 2026, SDC payment is required prior to permit issuance. The total cost to the homeowner is higher in 2026 than it was in 2025 for the same scope.
When you’re getting side-sewer quotes in 2026 Seattle:
- Verify the contractor is SPU-registered (separate from L&I SCBR).
- Verify the quote includes the SPU permit fee plus drainage SDCs.
- Verify SDOT ROW permit is included if work crosses sidewalk or street.
When you’ll encounter this term
- A pre-purchase sewer scope revealing compromised side sewer.
- A backed-up sewer line traced to a collapsed or root-bound side sewer.
- A new ADU or DADU project requiring a separate side-sewer connection.
- A sewer replacement quote referencing SPU permit and SDOT ROW permit.
Common variants and disambiguation
- SPU side sewer permit vs. SDCI plumbing permit. SDCI plumbing permit covers in-building plumbing and the building drain up to the foundation. SPU side sewer permit covers everything from the foundation to the public main. Both may be required on a sewer-line replacement.
- SPU side sewer permit vs. SDOT permit. SDOT covers right-of-way (street or sidewalk) work. If the side sewer excavation crosses or occupies the ROW, both SPU and SDOT permits apply.
- Pre-2025 SDCI side sewer permit vs. post-2025 SPU. Same regulatory authority migrated to SPU on 10/1/2025. Permit forms and contact info changed; the regulatory basis (SMC 21.16) is the same.
- SPU side sewer permit (Seattle) vs. Tacoma side sewer permit. Tacoma has its own permit under Tacoma Municipal Code; not interchangeable. Other WA cities have their own analogous permits.
Washington note
For Seattle homeowners, the SPU side sewer permit transition timeline:
- Through September 30, 2025: SDCI issued side sewer permits.
- October 1, 2025 forward: SPU issues side sewer permits. Side sewer plan review, permitting, and inspection are SPU’s responsibility.
- January 1, 2026: Drainage System Development Charges (SDCs) added to side sewer permit invoicing.
- May 4, 2026: SDC payment required prior to permit issuance.
For non-Seattle WA jurisdictions, side sewer permits are handled by:
- Tacoma: Tacoma Permits under Tacoma Municipal Code.
- Bellevue: City of Bellevue Development Services / Public Works.
- King County (unincorporated): King County DLS or Wastewater Treatment Division depending on connection type.
- Spokane, Snohomish, Pierce: county or city building/wastewater department.
The SPU-registered contractor requirement is unique to Seattle; other WA jurisdictions have their own contractor-eligibility rules. Verify with the local AHJ before quoting.