What Documents Should Every Septic Homeowner Have on File?
Most homeowners don't know what's buried in their yard — literally. Your as-built drawing, O&M permit, and inspection reports are public record and tell the whole story. Here's what to find and why it matters.
What Documents Should Every Septic Homeowner Have on File?
Most homeowners know they have a septic system somewhere in their yard. Fewer know where it is, what type it is, or what the county has on file about it. Here's exactly what you should have — and how to get it if you don't.
1. The As-Built Drawing
This is the most important document. An as-built (or "as-built plan") is a scaled diagram showing:
- The exact location of your septic tank, distribution box, and drain field on your property
- Tank size and type (gravity, LPD, mound, ATU, etc.)
- Setbacks from your house, property lines, and water features
- Installation date and permit number
As-builts are filed with your county health department and are public record — anyone can request them. If you don't have yours, call Snohomish, Skagit, or Island County Environmental Health and provide your parcel number.
Why it matters: Without an as-built, a technician may spend 30–60 minutes just locating your tank. That's time and money you don't need to spend. And if you're selling your home, buyers and their agents will ask for it.
2. The Onsite Sewage Disposal System (OSS) Permit
When your system was installed or repaired, a permit was issued. This document includes:
- System type and design specifications
- Number of bedrooms the system was sized for
- Installer and designer information
- Health department approval signatures
If your home is older, this permit may date back decades — but it's still valid and searchable by parcel number at your county health department.
3. O&M Contract (ATU Owners Only)
If you have an aerobic treatment unit (ATU), Washington State law requires you to maintain an active Operation & Maintenance contract with a licensed provider. This contract — and your inspection reports — must be on file with the county.
If you've lost your O&M records or your previous provider went out of business, Blackwater Services can help you get back into compliance.
4. Past Pump-Out Records
Whenever your tank is pumped, the service provider should give you a receipt noting:
- Date of service
- Tank size and condition
- Sludge and scum levels
- Any noted deficiencies
Keep these. They're your maintenance history and can be critical during a home sale or insurance claim.
5. Inspection Reports
Any formal inspection — whether for county compliance, a real estate transaction, or ATU maintenance — generates a written report. Keep all of these in a folder (physical or digital).
How to Get Your Documents If You Don't Have Them
- Snohomish County: Request records at snohomishcountywa.gov or call (425) 339-5250
- Skagit County: Contact Environmental Health at (360) 416-1500
- Island County: Call (360) 679-7350 or visit islandcountywa.gov
Alternatively, call Blackwater Services at (425) 777-4545 — we can often pull your county records as part of a scheduled service visit and walk you through everything in plain language.
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.
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