Aerobic Septic Systems in Washington State: What Homeowners Must Know
Aerobic Treatment Units (ATUs) require mandatory biannual inspections under Washington State law. Here's everything you need to know about ATU ownership, compliance, and maintenance costs.
Aerobic Septic Systems in Washington State
If your home has an aerobic treatment unit (ATU), you have a more advanced — and more regulated — system than a conventional septic tank. Here's what you need to know.
What Is an Aerobic Treatment Unit?
An ATU uses oxygen injection to break down waste more completely than conventional anaerobic systems. The result is a cleaner effluent that can be safely dispersed in areas where conventional systems can't be used — near waterways, on small lots, or in sensitive shoreline zones.
Washington State Compliance Requirements
Under WAC 246-272A, ATU owners in Washington State are legally required to:
- Maintain an active O&M (Operation & Maintenance) contract with a licensed provider
- Have the system inspected at least twice per year (every 6 months)
- Submit inspection reports to the county health department
Non-compliance can result in fines, enforcement actions, and loss of your system's operating permit.
What Happens During an ATU Inspection?
A certified technician checks:
- Aerator/blower function and air flow rates
- Effluent clarity and treatment quality
- Alarm systems and control panels
- Disinfection system (chlorine tablet dispenser or UV)
- Tank solids levels and pump function
Common ATU Brands We Service
Blackwater Services is certified to maintain all major ATU systems including:
- Norweco Singulair
- Bio-Microbics FAST
- NuWater BNR
- OSCAR XO2
- Jet
- Clearstream
The Blackwater Protection Plan
Our Protection Plan starts at $99/month for ATU systems and covers both mandatory annual inspections, priority scheduling, and up to $1,000 in annual repair credits.
Call (425) 777-4545 to get enrolled and stay compliant.
Written by
Zebulun Tilton
Founder & Certified Lead Septic Technician — Blackwater Services
Zebulun has over a decade of hands-on experience in septic pumping, repair, and aerobic ATU maintenance across Snohomish, Skagit & Island Counties, WA. He holds a Washington State Contractor Registration (CCBLACKS*793NT) and is certified on all major ATU systems including Norweco, Bio-Microbics, NuWater BNR, and OSCAR XO2.
Need Septic Help in Western Washington?
Same-day service available. Licensed, insured, and women-owned. Serving Snohomish, Skagit & Island Counties.
Call (425) 777-4545Protect Your Septic System Today
Schedule service, ask questions, or enroll in a Protection Plan. Blackwater Services is available 24/7.
No obligation. Licensed & insured. Serving Snohomish, Skagit & Island Counties.
