Test a private well at least once a year for total coliform bacteria, nitrate, total dissolved solids and pH, as the CDC and EPA recommend. Add tests for arsenic, lead, manganese, uranium or radon based on your area and plumbing, and retest after flooding, repairs or a change in taste, smell or color. Use a state-certified lab.
City water is tested by the utility. A private well is tested by you. Treatment choices, from a UV system to a softener or iron filter, all depend on these results.
The annual baseline
| Test | Why |
|---|---|
| Total coliform bacteria | Signals a path for surface contamination |
| Nitrate | Fertilizer, septic and animal sources; risky for infants |
| Total dissolved solids | General water quality and treatment sizing |
| pH | Corrosive water can leach metals from plumbing |
Add these based on where you live
| Test | When |
|---|---|
| Arsenic | Common in some regions’ bedrock; ask your state or county health department |
| Lead and copper | Older plumbing or low-pH water |
| Iron and manganese | Staining, metallic taste or black or orange deposits |
| Hardness | Scale on fixtures, soap that will not lather |
| Hydrogen sulfide | Rotten-egg smell |
| Uranium and radon | Granite and some other geologies |
| PFAS | Near airports, military bases, industrial sites or areas with known contamination |
Test again when
- After flooding near the wellhead
- After any well repair or new pump
- When taste, smell or color changes
- When someone in the house is pregnant or there is an infant
How to sample
Use the lab’s bottles and instructions. Bacteria samples are usually taken from a cold tap after removing the aerator, disinfecting the spout and running the water, then delivered to the lab within a set number of hours. Do not sample through a filter or softener unless you are testing the treatment itself.
Choosing a lab
Your state health or environmental agency lists certified drinking-water labs. Mail-in national services exist too; check that the lab doing the analysis is certified.
From results to treatment
Bacteria point to fixing the source and possibly UV disinfection. Hardness points to a softener. Iron, manganese and sulfur need dedicated filters, covered in our whole-house filter guide. Check any product against its certification listing.
Common questions
How often should I test my well water?
At least once a year for bacteria and nitrate, and again after floods, well repairs or any change in taste, odor or appearance.
Who regulates private well water?
In the US, the EPA does not regulate private wells. The owner is responsible for testing and treatment.
Are home test strips good enough?
Strips are useful for hardness, pH and chlorine checks, but bacteria, nitrate and metals should be tested by a certified lab.
What is the safe limit for nitrate?
The EPA drinking water limit for public systems is 10 mg/L as nitrogen. Infants are most at risk above it.