Design and permit compliant septic systems for rural Washington properties. Soil testing, health department approval, conventional and alternative systems. Build with confidence.
Start Septic DesignEvery home without municipal sewer needs a permitted septic system. Washington's Department of Health and local health districts regulate septic design to protect groundwater and public health. You can't build or get occupancy without an approved, installed, and inspected septic system.
TerraVector coordinates the entire septic process: soil testing (percolation and profile), system design by licensed engineers, health department permit applications, installer coordination, and final inspection. We work with conventional gravity systems, pressure distribution, mound systems, and alternative technologies across Washington counties.
Assess property for suitable septic locations based on slopes, setbacks, and building placement.
Dig test pits to evaluate soil type, depth to limiting layer, and percolation rate.
Engineer designs septic tank, drainfield, and distribution method based on soil conditions and bedroom count.
Submit design to local health department with soil logs, site plan, and engineering calculations.
Licensed septic installer excavates, places tank, constructs drainfield per approved design.
Health department inspects completed system. Permit closed and approved for use.
Design and permitting costs $3K–$6K (soil testing, engineering, health department fees). Installation costs $10K–$25K+ depending on system type. Conventional gravity systems cost $12K–$18K. Pressure distribution or mound systems cost $18K–$30K. Advanced treatment systems cost $25K–$50K.
Poor-draining soils don't mean you can't build — you'll need an alternative system. Options include: pressure distribution to larger drainfield, mound system above grade, sand filter, or advanced treatment unit. These systems cost more but work on challenging sites.
Minimum lot size varies by county and soil type. Typical requirements: 1/2 acre for conventional systems in good soil, 1+ acre for marginal soils or alternative systems. You also need reserve area (backup drainfield location) equal to the primary drainfield size.
Soil testing and design take 2–3 weeks. Health department review averages 3–6 weeks depending on county workload and complexity. Installation takes 1–2 weeks once permitted. Total timeline: 6–12 weeks from site evaluation to final inspection.
No. Washington requires septic designs be prepared by licensed engineers, licensed designers, or health department-approved soil scientists. DIY designs won't be approved. Installation also requires licensed contractors.
Typical Washington setbacks: 100 feet from wells (yours or neighbors'), 50 feet from streams/lakes, 20 feet from property lines, 10 feet from building foundations, 5 feet from driveways. Exact requirements vary by county — we'll verify for your location.
Pump septic tanks every 3–5 years depending on household size and tank capacity. Inspect system annually. Alternative systems (aerobic units, sand filters) require more frequent maintenance and often have service contracts. Regular maintenance prevents costly failures.
We coordinate septic system design and permitting across central and eastern Washington: Grant, Adams, Douglas, Lincoln, Franklin, Okanogan, Spokane, Kittitas, and Chelan counties.
Tell us about your property and building plans. We'll coordinate soil testing, engineering, and health department approval.
Start Septic Design