Septic inspection when selling a house in Washington
1 statewide rule and 6 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: septic system at sale Starts February 1, 2027
| Question | What the official text says |
|---|---|
| What is required | OSS inspected under WAC 246-272A-0260(5) by a third-party inspector authorized by the local health officer; results on officer-approved form to LHJ; also seller gives buyer maintenance records and seller disclosure Source: app.leg.wa.gov |
| Triggered by | sale or transfer of property with an OSS (inspection duty from 2027-02-01) Source: app.leg.wa.gov |
| Deadline | at time of property transfer (third-party inspection from 2027-02-01) Source: app.leg.wa.gov |
| Who arranges it | owner Source: app.leg.wa.gov |
| Exemptions |
Source: app.leg.wa.gov |
| If the system fails | Health officer may require a compliance schedule for repairs if failure found at transfer Source: app.leg.wa.gov |
| In force since | February 1, 2027 Source: app.leg.wa.gov |
Checked on November 9, 2026: read on the official site.
Local rules in Washington (6)
| Where | What | When | Rule set by |
|---|---|---|---|
| Clallam County | Septic system | Every property transfer: the owner gives the buyer a current system status report, done… | Clallam County Environmental Health |
| Island County | Septic system | before closing; ideally at time of offer | Island County Public Health |
| King County | Septic system | before closing; Public Health reviews within 10 business days | Seattle & King County Public Health |
| Pierce County | Septic system | before sale; TPCHD aims to review within 10 business days | Tacoma-Pierce County Health Department |
| Skagit County | Septic system | inspection dated within 6 months of closing | Skagit County Public Health |
| Thurston County | Septic system | application submitted for Time of Transfer report | Thurston County Public Health & Social Services |
1 page above still lack some details from the official text; they are kept out of search results until we have read more of the rule.
When the local rules started
4 local rules in Washington state a start date in the official text we read; the other 2 do not.
- 2006 Skagit County (April 3, 2006)
- 2008 Island County (2008)
- 2010 Clallam County (June 1, 2010)
- 2010 Thurston County (September 1, 2010)
Published costs in Washington
Fee items from official fee schedules and guides, with the year each applies to. They are different items (acceptance fees, inspections, escrow), so we list them rather than average them.
| Jurisdiction | Item | Amount | Year | Source |
|---|---|---|---|---|
| Island County | septic inspection at sale (provider charges) | $100 to $500 | 2026 | islandcountywa.gov |
| Skagit County | inspection rebate for qualifying residents | up to $100 | 2026 | skagitcountywa.gov |
Private wells in Washington
About 1,023,853 of Washington’s 7,170,351 residents (14%) got their drinking water from a private well in 2015, by the USGS estimate. The 6 counties with a whole-county rule listed here hold about 315,077 of them (31%); the largest by well users: King County (128,846), Pierce County (65,912), Thurston County (61,985).
Source: USGS county water use 2015 (Dieter et al., 2018); 39 counties in the USGS table.
Where private wells (and usually septic systems) are most common
Washington ranks 17 of 45 states and territories by people on private wells (USGS 2015). In 3 of its 39 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:
- Ferry County: 66% of 7,582 residents on a private well
- Pend Oreille County: 66% of 13,088 residents on a private well
- San Juan County: 54% of 16,252 residents on a private well
- Okanogan County: 50% of 41,516 residents on a private well
- Lewis County: 49% of 75,882 residents on a private well
- Stevens County: 49% of 43,791 residents on a private well
- Skamania County: 40% of 11,339 residents on a private well
- Klickitat County: 40% of 21,026 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 Washington
Across the 12 counties with USDA soil survey data, 81% of rated land is “very limited” for a conventional septic drain field. Most limited: Island County (100%), San Juan County (100%), Stevens County (96%). Least limited: Adams County (59%), Franklin County (60%), Grant County (78%).
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
Washington has a statewide rule. Of its 2 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:
- Oregon: statewide well water test rule at sale.
Washington health jurisdictions and the 2027 rule
From February 1, 2027 the state rule applies everywhere in Washington. Each local health jurisdiction decides which inspectors it authorises and which form to use. What each one’s own page said when we checked:
| Health jurisdiction | Counties | Page describes a sale inspection | Official page |
|---|---|---|---|
| Adams County Integrated Health Care Services | Adams | Not yet | co.adams.wa.gov |
| Asotin County Health District | Asotin | Not yet | ac-hd.org |
| Benton-Franklin Health District | Benton, Franklin | Not yet | bfhd.wa.gov |
| Chelan-Douglas Health District | Chelan, Douglas | Not yet | cdhd.wa.gov |
| Clallam County Health and Human Services | Clallam | Yes | clallamcountywa.gov |
| Clark County Public Health | Clark | Yes | clark.wa.gov |
| Columbia County Public Health | Columbia | Not yet | columbiacopublichealth.org |
| Cowlitz County Health and Human Services | Cowlitz | Not yet | co.cowlitz.wa.us |
| Garfield County Health District | Garfield | Not yet | garfieldcopublichealthwa.gov |
| Grant County Health District | Grant | Yes | granthealth.org |
| Grays Harbor Public Health and Social Services | Grays Harbor | Not yet | graysharbor.us |
| Island County Public Health | Island | Yes | islandcountywa.gov |
| Jefferson County Public Health | Jefferson | Yes | jeffersoncountypublichealth.org |
| Kitsap Public Health District | Kitsap | Yes | kitsappublichealth.org |
| Kittitas County Public Health | Kittitas | Could not open the page | co.kittitas.wa.us |
| Klickitat County Public Health | Klickitat | Not yet | klickitatcounty.gov |
| Lewis County Public Health and Social Services | Lewis | Could not open the page | lewiscountywa.gov |
| Lincoln County Health Department | Lincoln | Yes | healthylincowa.com |
| Mason County Public Health | Mason | Yes | masoncountywa.gov |
| Northeast Tri County Health District | Ferry, Pend Oreille, Stevens | Yes | netchd.org |
| Okanogan County Public Health | Okanogan | Could not open the page | okanogancounty.gov |
| Pacific County Health and Human Services | Pacific | Yes | co.pacific.wa.us |
| San Juan County Health and Community Services | San Juan | Not yet | sanjuancountywa.gov |
| Seattle and King County Public Health | King | Yes | cdn.kingcounty.gov |
| Skagit County Public Health | Skagit | Yes | skagitcountywa.gov |
| Skamania County Community Health (septic program run by Community Development, Environmental Health Division) | Skamania | Yes | skamaniacounty.gov |
| Snohomish County Health Department | Snohomish | Yes | snohd.org |
| Spokane Regional Health District | Spokane | Yes | srhd.org |
| Tacoma-Pierce County Health Department | Pierce | Yes | tpchd.org |
| Thurston County Public Health and Social Services | Thurston | Yes | thurstoncountywa.gov |
| Wahkiakum County Public Health and Human Services | Wahkiakum | Not yet | co.wahkiakum.wa.us |
| Walla Walla County Community Health | Walla Walla | Not yet | dch.co.walla-walla.wa.us |
| Whatcom County Health Department (Health and Community Services) | Whatcom | Yes | whatcomcounty.us |
| Whitman County Public Health | Whitman | Yes | whitmancountypublichealth.org |
| Yakima Health District | Yakima | Yes | yakimacounty.us |
Well water test: 44 labs on the Washington certified drinking-water list (WA Ecology - Environmental Laboratories Accredited for Drinking Water Analyses (with scopes), Information current as of 11/13/2026) are marked as taking samples from homeowners or outside clients and certified for coliform bacteria. See certified well-water labs and testing advice in Washington.
Other states: all states.