Licensed Septic Contractors: King County, WA

85 licensed septic contractors based in King County. Every license number below is sourced from public licensing records, with a link to look it up yourself.

Grouped by the county of the address on each license record, which can be a mailing address, so it doesn't tell you where the business works. When the record names no county, we place it by ZIP code, then town.

Checked against King County Public Health - Master Installers (OSS) + King County Public Health - Onsite System Maintainers, King County Public Health - Onsite System Maintainers, Washington State Dept. of Health - Credential Search, King County Public Health - Master Installers (OSS) + King County Public Health - Onsite System Maintainers + King County Public Health - Certified Liquid Waste Pumper/Hauler, King County Public Health - Master Installers (OSS), King County Public Health - Certified Liquid Waste Pumper/Hauler, King County Public Health - Onsite System Maintainers + King County Public Health - Certified Liquid Waste Pumper/Hauler and King County Public Health - Master Installers (OSS) + King County Public Health - Certified Liquid Waste Pumper/Hauler. Roster copy last refreshed 2026-08-19.

Towns in King County

All 21 towns named on the license records based here, with the number of listings in each, most first.

License classes on the King County records

Each class as the issuing agency prints it on the license record. A record that names more than one class counts once under each, so the rows can add up to more than 85.

Septic Contractors based in King County (85)

Licensed by King County

King County issued these businesses' licenses, but the address on their license record is not in King County.

Own one of these businesses? Find your listing and claim it.

Looking for a specific contractor? Search by name, business name, or license number.

Services in King County, with national cost ranges

Listings based in King County whose license class covers each service. Cost ranges are national; each links its cost guide.

None of the listings based in King County hold a license class we can match to perc test and soil evaluation. Ask any contractor whether they do this work, or try a nearby city.

Hiring a septic contractor in King County

Septic (onsite wastewater) contractors handle everything from routine septic tank pumping and cleaning to repairs, inspections, and new system installation. States license each role separately (a pumper is not necessarily licensed to install, and vice versa), so match the license class to the job.

Before you sign anything: confirm the license on this page is still active with the agency that issued it, ask for proof of insurance, and get at least three written quotes; pricing on this work varies widely by site conditions.

Neighboring counties