King County County · Pop. 749,256
Seattle and King County represent one of the most challenging septic system environments in the Pacific Northwest due to the combination of glacially-derived soils with restrictive till layers, high seasonal rainfall, and the ecological sensitivity of Puget Sound. Although Seattle's urban core is entirely sewered, King County is home to over 85,000 permitted onsite sewage systems serving rural communities on the Eastside, Enumclaw Plateau, Vashon Island, and other areas. King County's OSS program is among the most rigorous in Washington State, with mandatory O&M reporting, biennial inspection requirements for many alternative system types, and enhanced standards for systems near Puget Sound shorelines. Alderwood soils, which cover much of King County's forested uplands, are well-known for their cemented till layer that perches groundwater and limits system options to mound or drip irrigation designs.
Holding Tank Pumping Services in Seattle - Green Latrine provides professional septic services in Seattle, WA and surrounding areas. Contact them for septic pumping, repair, and inspection services.
Seattle, WA
Scott's Septic Service provides professional septic services in Seattle, WA and surrounding areas. Contact them for septic pumping, repair, and inspection services.
Spokane, WA
DOWNRIVER SEPTIC provides professional septic services in Spokane, WA and surrounding areas.
H&R Complete Septic Pumping and Excavation - Spokane Kootenai provides professional septic services in Spokane, WA and surrounding areas.
Septic System Installation & Repair Spokane, WA - Vietzke Trenchless provides professional septic services in Spokane, WA and surrounding areas.
Septic System Repair Near Me - Spokane - Bulldog Rooter provides professional septic services in Spokane, WA and surrounding areas.
$2,000 – $15,000
$200 – $800
$300 – $600
$3,500 – $20,000
$275 – $600
$500 – $5,000
$6,000 – $25,000
$300 – $3,000
$50 – $500
$500 – $8,000
| Service | Average Cost |
|---|---|
| Septic Tank Pumping | $300 - $550 |
| Septic System Installation | $12,000 - $35,000 |
Seattle and King County soils are dominated by Alderwood gravelly sandy loam—a glacially-derived, moderately well-drained soil over dense glacial till ortstein layer typically found at 20 to 40 inches depth. The ortstein or cemented till layer severely restricts percolation below that depth, causing perched seasonal groundwater. Norma fine sandy loam and Tukwila muck occur in lowlands and are hydric soils unsuitable for conventional systems.
Alderwood gravelly sandy loam (USDA series) is the dominant soil across King County uplands, characterized by 20 to 40 inches of moderately permeable material over a dense, nearly impermeable glacial till ortstein. This profile causes perched seasonal groundwater that saturates the lower half of conventional drainfields. Norma fine sandy loam and Tukwila muck in valley bottoms are hydric soils classified as unsuitable for any type of OWTS. Indianola loamy sand, present on higher-elevation outwash terraces, has good permeability and is the most favorable soil for conventional systems in King County.
King County Environmental Health Services administers OSS permits under WAC 246-272A with locally-adopted additional requirements. All new systems require a licensed OSS designer evaluation. Systems within 200 feet of Puget Sound, Lake Washington, or other listed water bodies require enhanced treatment technology. King County mandates biennial inspections for ATUs, drip irrigation, and mound systems. O&M reports must be submitted electronically to King County's OSS tracking database.
Seattle proper is entirely connected to King County's regional sewer system. Rural King County unincorporated areas and smaller cities use OSS permitted by King County Environmental Health Services under WAC 246-272A. King County requires a licensed OSS designer evaluation, annual or biennial inspections for many alternative systems, and O&M reporting via King County's online tracking system.
Septic contractors in the surrounding region