FAQ
Septic and Well Due Diligence for Washington Buyers
Septic and private-well systems are expensive, largely invisible at a showing, and central to rural-property due diligence in Snohomish, Skagit, and rural King County.
Septic records and capacity
Form 17 identifies the system type and last inspection or pumping. Compare it with county health records, including permits, as-builts, and inspection history. Snohomish and Skagit County health departments maintain online on-site septic records.
The offer should state who pays for inspection and pumping, whether reports are provided, and what happens if evaluation fails. King County has Form 22S-King; elsewhere these terms are written into the offer. Match permitted capacity with bedroom count.
Well testing and shared systems
Request a flow test in gallons per minute and water-quality testing for bacteria and nitrates. Arsenic may be worth adding in parts of the region. Confirm the well log with Department of Ecology records and understand water-right limits for irrigation.
For a shared well, obtain the recorded agreement covering maintenance costs, easements, and usage before contingencies run. Lenders will require it.
Build it into the deadline
Put septic and well inspections inside the Form 35 contingency window and use Form 35R if findings justify negotiation. These are normal diligence items, but they need time.
Sources: NWMLS Forms 17, 22S-King, 35, 35R; county health district on-site septic records. This is general information, not legal advice.
Next Steps for Buyers
Use seller disclosures as the starting point for system questions.
Build specialized checks into the inspection window.
See how findings can turn into a negotiation.
Explore a market with many septic and well properties.
Explore north-county property context.
Common Buyer Questions
What should a buyer check on a septic system in Washington?
Verify the seller's Form 17 answers against county health department records, confirm permitted capacity matches the bedroom count, and negotiate in the offer who pays for the inspection and pumping and what happens if the system fails evaluation.
What testing should a buyer do on a private well?
At minimum a flow test and water quality testing for bacteria and nitrates, with the well log confirmed against Department of Ecology records. Shared wells require reviewing the recorded shared well agreement, which lenders will ask for.
Who pays for the septic inspection when buying a home in Washington?
It is negotiable and should be addressed in the offer. Septic pumping and inspection at sale is commonly a seller cost by custom in much of Washington, but nothing makes that automatic, so the offer should state it explicitly.