Well water test when selling a house in Oregon
1 statewide rule and 0 local rules from official sources.
General information, not legal advice. This is our summary of the official rule as we read it. The ordinance or code and the health department decide: confirm with them before you list, sign or close.
Statewide: well water test at sale
Domestic wells. Spring wells, irrigation-only wells and wells on undeveloped land are exempt. Tests: arsenic, nitrate and total coliform bacteria.
| Question | What the official text says |
|---|---|
| What is required | Seller tests domestic well for arsenic, nitrate and total coliform at an accredited lab; sends results to buyer and OHA within 90 days Source: oregon.gov |
| Triggered by | sale of a property with a domestic well Source: oregon.gov |
| Deadline | The seller has 90 days to send a copy of the results to the buyer (the page does not say from when) Source: oregon.gov |
| Who arranges it | seller or representative Source: oregon.gov |
| How long a report is valid | results valid 1 year, usable for multiple offers Source: oregon.gov |
| Exemptions |
Source: oregon.gov |
| Well part | Arsenic, nitrate, total coliform bacteria; deliver sample to lab within 24h Source: oregon.gov |
| Official forms | oregon.gov Source: oregon.gov |
Checked on November 9, 2026: read on the official site.
Private wells in Oregon
About 631,538 of Oregon’s 4,028,977 residents (16%) got their drinking water from a private well in 2015, by the USGS estimate.
Source: USGS county water use 2015 (Dieter et al., 2018); 36 counties in the USGS table.
Where private wells (and usually septic systems) are most common
Oregon ranks 21 of 45 states and territories by people on private wells (USGS 2015). In 2 of its 36 counties more than half of residents drink from a private well; homes there usually also treat wastewater on site, so a septic check and a well test tend to come up together at sale. The highest shares:
- Lake County: 57% of 7,829 residents on a private well
- Josephine County: 54% of 84,745 residents on a private well
- Wheeler County: 45% of 1,358 residents on a private well
- Crook County: 44% of 21,630 residents on a private well
- Polk County: 44% of 79,391 residents on a private well
- Harney County: 35% of 7,200 residents on a private well
- Wallowa County: 35% of 6,856 residents on a private well
- Grant County: 35% of 7,185 residents on a private well
USGS county water use 2015 (Dieter et al., 2018). The USGS table counts well users, not septic systems; no national county count of septic systems exists.
Soils for septic drain fields in Oregon
Across the 13 counties with USDA soil survey data, 95% of rated land is “very limited” for a conventional septic drain field. Most limited: Curry County (100%), Josephine County (100%), Clatsop County (99%). Least limited: Sherman County (74%), Gilliam County (81%), Benton County (93%).
Source: USDA NRCS Soil Survey Geographic Database (SSURGO), via Soil Data Access, rating “ENG - Septic Tank Absorption Fields”, read November 15, 2026. County-wide ratings, not a test of one lot.
How the neighbouring states compare
Oregon has a statewide rule. Of its 4 neighbouring states, 1 has a statewide rule at sale; a buyer moving across the line may meet a different rule. From our register of official rules:
- Washington: statewide septic system rule at sale plus 6 local rules.
- California: no statewide rule; 1 local rule (counties, cities or townships).
Well water test: 37 labs on the Oregon certified drinking-water list (ORELAP laboratory search (ODIE): accredited for the Drinking Water matrix, search as fetched 2026-11-15 (live database, no list date)) are marked as taking samples from homeowners or outside clients and certified for coliform bacteria. See certified well-water labs and testing advice in Oregon.
Other states: all states.