Oregon county well guide

Well Water in Washington County, OR: Testing, Contractors and Rules

About 20,173 households in Washington County, 9% of the county, rely on a private well. Nobody tests that water unless the owner does.

Labs within 40 milesLicensed contractors
9%of households on a private well
Share on wells, county vs state
Washington County9%
Oregon average16%
25licensed contractors serve the county
<1 mito the nearest certified lab, Apex Laboratories, LLC
Yesstatewide test required when a home is sold

Roughly 9% of Washington County households, about 20,173, get their water from a private well rather than a utility. They are concentrated in the rural parts of the county, and they are on their own for testing.

Local rules for wells in Washington County

Private wells in Washington County follow Oregon's statewide rules, administered by Oregon Water Resources Department, Well Construction and Compliance Section. No water test is required by the state when a new well is completed. A test is also required when a home with a well is sold. The cards below show the details and the official sources.

At a glance

Water test for a new wellNot required statewide

No statewide water test on a new well. The well must be built by an OWRD-licensed, bonded water supply well constructor (or by the landowner under a Landowner's Water Well Permit) to the OAR 690-210 standards, with a start card filed and the fee paid before drilling, a metal well ID tag attached, and a well report filed with OWRD within 30 days. Setbacks are 50 ft from a septic tank and 100 ft from a drainfield. Some counties ask for a bacteria test before a building permit is finaled, and lenders usually do.

Water test when a home is soldRequired

Yes. Oregon's Domestic Well Testing Act (ORS 448.271, OAR 333-061-0305 to 0335) requires the seller of a property with a domestic well to have the water tested by an ORELAP-accredited lab for arsenic, nitrate and total coliform bacteria, give the results to the buyer and report them to the Oregon Health Authority within 90 days of the sale. It is one of only a handful of state laws in the country that test private wells at transfer.

What the state recommends

The Oregon Health Authority recommends testing a domestic well every year for coliform bacteria and nitrate, and every three to five years for arsenic (found across the Willamette Valley, the Tualatin basin, Lane County and Klamath and Lake counties), plus pH, hardness, iron, manganese, lead and copper once. Add uranium and radon in Lane County and the Cascade foothills, and test again after flooding, well work or a change in taste, color or smell. In the Southern Willamette Valley and Lower Umatilla Basin Groundwater Management Areas, nitrate is the test that matters most.

Free or low-cost testingAvailable

No statewide free program. The OSU Extension Well Water Program runs free nitrate screening clinics around the state and publishes testing guidance, and Oregon Health Authority's Domestic Well Safety Program (971-673-0440) helps owners read results. The Lower Umatilla Basin (Morrow and Umatilla counties) has state-funded free nitrate testing and water delivery for affected wells. Otherwise the ORELAP labs below charge $30 to $60 for bacteria and nitrate and $150 to $250 for the real estate panel.

Getting your water tested near Washington County

7 certified labs within 40 miles serve Washington County, starting with Apex Laboratories, LLC in Tigard (in the county). Each card below shows whether the lab takes homeowner samples and which tests it is certified for.

6 certified labs within 40 miles

Licensed well contractors serving Washington County

25 licensed contractors serve Washington County, including A J Gaunt and Son and All Seasons Well Drilling. Each profile carries the state license number and the date we checked it, and the filters below sort them by drilling, pump work or treatment.

Well depth and water chemistry

Wells in Washington County typically reach 160 to 400 feet; the median of 2,040 new domestic wells reported to OWRD since 2000 is 260 feet. What comes up with the water depends on the aquifer, and across Oregon the usual suspects are arsenic (naturally occurring across the willamette valley, the tualatin basin, lane county, the klamath and lake basins and parts of central oregon). A first full panel tells you which of them apply to your well.

Typical well depth

160 to 400 feet; the median of 2,040 new domestic wells reported to OWRD since 2000 is 260 feet

Contaminants to test for
  • Arsenic (naturally occurring across the Willamette Valley
  • The Tualatin basin
  • Lane County
  • The Klamath and Lake basins and parts of central Oregon)
  • Nitrate (Southern Willamette Valley
  • Lower Umatilla Basin and Northern Malheur groundwater management areas
  • And shallow wells in farm country)
  • Coliform bacteria (statewide
  • Worst in shallow and older wells)
  • Iron and manganese (valley alluvium and coastal sands)
  • Hardness (basalt and limestone areas)
  • Uranium and radon (Lane County granite and Cascade foothills)
  • Hydrogen sulfide (deep basalt wells)
  • Sodium and boron (some Willamette Valley aquifers)
  • PFAS near airfields and industrial sites

Neighboring counties: Multnomah County, Clackamas County, Yamhill County, Columbia County.

What well work costs in Washington County

Bacteria test (coliform and E. coli)$20 to $40published Oregon lab fees
Nitrate test$20 to $40published Oregon lab fees
Broad panel (metals and minerals)$85 to $450state and university lab packages
Well inspection$250 to $550$350 to $900 with water testing
Submersible pump replacement$1,000 to $2,500installed; deep wells cost more
Pressure tank replacement$800 to $1,500installed
One treatment unit$700 to $3,500softener, iron filter or UV, installed
Multi-stage whole-house treatment$2,500 to $10,000+several units or whole-house RO, installed
New well, complete$6,000 to $16,000typical 200 ft well with pump; drilling alone about $20 to $30 per foot; deeper wells cost more
Shock chlorination$80 to $200by a contractor; under $30 to do yourself

Oregon Health Authority estimates; arsenic runs $25 to $45. Installed costs are national 2026 ranges; local quotes vary with depth, access and materials. Sources, checked September 2026: Oregon Health Authority testing recommendations, HomeGuide cost guides, Angi: cost to shock a well.

Questions Washington County well owners ask

How many homes in Washington County are on a well?

About 20,173, or 9% of households, based on Census housing data and state well surveys. The share is highest outside the towns with public water.

Where is the closest certified lab to Washington County?

Apex Laboratories, LLC in Tigard, inside the county. It accepts homeowner samples.

Do I need a permit to drill a well in Washington County?

No statewide water test on a new well. The well must be built by an OWRD-licensed, bonded water supply well constructor (or by the landowner under a Landowner's Water Well Permit) to the OAR 690-210 standards, with a start card filed and the fee paid before drilling, a metal well ID tag attached, and a well report filed with OWRD within 30 days. Setbacks are 50 ft from a septic tank and 100 ft from a drainfield. Some counties ask for a bacteria test before a building permit is finaled, and lenders usually do.

What does a well test cost near Washington County?

Published lab fees in Oregon: $20 to $40 for a bacteria test and $20 to $40 for nitrate. Oregon Health Authority estimates; arsenic runs $25 to $45. Mail-in kits cost about the same as walking in.