Aerobic / ATU Septic System Cost in Washington
Estimated 2026 installed range: $10,200 – $23,000
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Statewide cost drivers here are hard ground, terrain and remote access. Locally, wet soils and strict local health rules drive design costs. That is why a aerobic / atu system in Washington can land well above or below the national range of $8,000–$18,000.
All system types in Washington
| System | Low | High |
|---|---|---|
| Conventional | $4,500 | $10,200 |
| Chamber | $6,400 | $14,100 |
| Aerobic / ATU | $10,200 | $23,000 |
| Mound | $12,800 | $28,200 |
| Sand filter | $10,200 | $20,500 |
What aerobic / atu systems are for
Aerobic treatment units add oxygen to break down waste faster. They are used on tight or wet lots, require electricity, and need periodic maintenance.
Related pages
All septic costs in Washington · Aerobic / ATU system overview