What's In Oregon's Tap Water?
An interactive guide to the most common drinking water contaminants found in Oregon tap water, public water systems, and private wells — plus the EPA health standards that protect you.
9 min read · Waterlab Corp Laboratory Staff
Public water vs. private well: Public water systems (cities, private well systems such as mobile home parks, down to simple water systems that serve more than 3 residences) are regulated by Oregon Health Authority and must publish annual Consumer Confidence Reports. Private well owners are responsible for testing their own water — there is no regulatory oversight.
Common Contaminants in Oregon Drinking Water
Coliform Bacteria & E. coli
CriticalPrimary sources
Poorly cased wells, flooding, nearby septic systems, surface water intrusion
EPA limit (MCL)
Absence or 0 (zero)
The most important baseline safety test for any private well. Wells can become contaminated after the system has been worked on, pipe replaced, flooding occurred around the well, the seal has not been maintained and needs replacement. These are not the only situations.
Arsenic
HighPrimary sources
Natural rock and soil in Oregon aquifers, especially in southern and eastern Oregon
EPA limit (MCL)
10 µg/L (ppb)
Oregon well water arsenic levels are among the highest in the Pacific Northwest. Private wells are not regulated and must be tested independently.
Nitrate-Nitrogen
High in ag areasPrimary sources
Agricultural fertilizers, septic systems, animal waste — common in Willamette Valley well water
EPA limit (MCL)
10 mg/L (ppm)
Nitrate-Nitrogen above the MCL is dangerous for infants under 6 months (blue baby syndrome). The Willamette Valley has elevated nitrate-nitrogen levels in many agricultural areas.
Lead
Moderate (older homes)Primary sources
Lead solder in plumbing (pre-1986 homes), lead service lines, brass fixtures
EPA limit (MCL)
Action level: 15 µg/L
Lead does not come from Oregon source water — it leaches from household plumbing. Homes built before 1986 are at highest risk. There is no acceptable level of lead in drinking water.
PFAS (Per- and Polyfluoroalkyl Substances)
Emerging concernPrimary sources
Military bases, industrial sites, firefighting foam, some consumer products
EPA limit (MCL)
EPA set MCL of 4 ppt for PFOA/PFOS (2024)
Oregon has confirmed PFAS contamination near several military sites. Public water systems are now required to test; private wells are not regulated.
Iron & Manganese
Aesthetic / equipmentPrimary sources
Natural minerals in Oregon groundwater, especially in the Willamette Valley
EPA limit (MCL)
Secondary standard: 0.3 mg/L iron, 0.05 mg/L manganese
Not a direct health hazard at typical levels, but causes staining, metallic taste, and damages water heaters and appliances. Common in Marion and Polk County wells.
Know what is in your water.
The only way to know for certain what is — and is not — in your water is to test it. Waterlab Corp provides accredited testing for all of the contaminants listed above and many more.