Do I need to test my well water? How often?
Nobody tests a private well but you. Oregon only requires it when a home is sold, but the Oregon Health Authority (OHA) recommends testing on a schedule.
Schedule a water test
OHA’s recommended schedule
Coliform & E. coli
Bacteria in the water.
Nitrate
Babies are at the highest risk.
Arsenic
Retest sooner if a result is high.
Test sooner if
The water’s color or taste changes. Oregon State University Extension says to test for bacteria right away.
A baby will drink the water, or formula made with it.
Someone in the house has a stomach illness.
The septic system failed, or well equipment broke or malfunctioned.
The well has had contamination before.
You’re selling the home. Then it’s required: see the home sale law.
What the results mean
| Test | What OHA says |
|---|---|
| Bacteria | None found: safe for all uses. Found: switch to bottled or another safe water source and look at treatment. |
| Nitrate | 10 mg/L or less is within the safe limit, though above 4 mg/L can be a sign of contamination. |
| Arsenic | The limit is 10 parts per billion. Retest if a result is above 8, and treat if high levels continue. |
Why would bacteria or nitrate get into a well?
OHA says it most likely means surface contamination is getting in. Fixes can include work around the wellhead, repairing the well system, or a treatment system. We can treat the water and retest after.
Stains, odd taste or smell?
Those usually aren’t covered by the basic tests. A water treatment or minerals test can find the cause, such as iron, manganese or hard water. Tell us what you’re seeing and we’ll pick the right test.
Let us take the sample
We collect it the right way, get it to an Oregon-accredited (ORELAP) lab in time, and go over the results with you.
Sources: Oregon Health Authority: Routine Domestic Well Testing · OHA: Coliform bacteria in well water · OHA: Arsenic and nitrate fact sheets · OSU Extension EM 8752. General information, not medical advice. Last checked November 2026.