What to test your private well water for (and how often)

Private well owners should test their water at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH. You should also test sooner when something changes, like flooding, a well repair, a new baby in the home, a change in taste or color, or a local contamination concern. (cdc.gov)

Start with the annual basics

Private wells are different from public water systems. Government agencies do not routinely regulate, treat, or monitor water from a private household well, so the owner is responsible for checking that it is safe to drink. CDC says to use a state-certified laboratory, and local health or environmental departments can often help explain which tests matter most where you live. (cdc.gov)

For most homes, the yearly starter panel is simple: total coliform bacteria, nitrate, total dissolved solids, and pH. Coliform testing helps flag whether germs may be getting into the well. Nitrate matters everywhere, and especially where septic systems, fertilizers, storm runoff, or animal waste may affect groundwater. pH and total dissolved solids do not tell the whole story, but they are useful water quality indicators that can point to corrosion, mineral buildup, or other changes worth a closer look at. (cdc.gov)

If you are not sure where to begin, use the Well water test planner to build a starting list, then find a lab through the state-by-state directory. If you want help comparing labs, this guide on How to choose a state-certified drinking water lab can help. (cdc.gov)

Add tests that fit your well and your area

The annual basics are only the floor, not the ceiling. EPA and CDC both say well owners should add tests based on local groundwater conditions, nearby land uses, household plumbing, and any changes around the well. (cdc.gov)

A practical checklist looks like this:

• If your plumbing or service line may contain lead: ask about testing for lead, copper, and pH. Low or high pH can damage pipes and let metals leach into water. (epa.gov)
• If you live in a farming area or near heavy fertilizer use: ask about nitrate, nitrite, pesticides, and coliform bacteria. (epa.gov)
• If a landfill, junkyard, factory, gas station, or dry cleaner is nearby: ask about volatile organic compounds, and depending on the local situation, total dissolved solids, pH, sulfate, chloride, and metals. (epa.gov)
• If you smell fuel or chemicals in the water: contact the health department right away. CDC says boiling or disinfection will not make fuel- or chemical-contaminated water safe. (cdc.gov)
• If your area is known for arsenic, radium, radon, mercury, or other naturally occurring contaminants: ask local officials or Extension which extra tests are recommended for your aquifer. CDC lists arsenic, mercury, radium, pesticides, herbicides, lead, and volatile organic compounds among the chemicals well owners may need to test for. (cdc.gov)
• If PFAS is a concern nearby: ask about PFAS if your area has known contamination from waste sites, fire-fighting foam use, or manufacturing waste, or if state or local officials have identified PFAS in groundwater. EPA says to work through your state environmental or health agency and use a state-certified lab that uses EPA-developed drinking water methods. (epa.gov)

Test sooner after changes, repairs, or bad weather

Do not wait for your next annual test if conditions around the well change. EPA and CDC both say to test right away if there are known groundwater problems in your area, flooding, land disturbance, nearby waste issues, well repairs, or a noticeable change in taste, color, or smell. CDC also says you should test when someone in the home becomes pregnant or when a child starts living there. (cdc.gov)

Flooding deserves special attention. EPA has separate guidance for wells after a flood, and CDC says disasters can damage well piping and electrical systems. After a disaster, CDC says it is safest to drink bottled water until you are sure the water is free of contaminants and safe to drink. If disinfection is needed after an emergency, CDC says to wait at least 7 to 10 days before testing so chlorine has time to flush out of the system. (epa.gov)

At a minimum, CDC says to check your well every spring for mechanical problems, even if the water seems normal. A damaged cap, cracked casing, poor drainage, or a recent pump or pipe repair can all be a reason to sample sooner. (cdc.gov)

Build a simple repeat schedule

A good routine for many homes is to do the basic yearly screen every 12 months and add targeted tests when local risk factors apply. That yearly screen is the one CDC and EPA agree on: total coliform bacteria, nitrates, total dissolved solids, and pH. (cdc.gov)

Beyond that, local guidance can vary. For example, University of Maryland Extension recommends annual testing for coliform bacteria and nitrates, and every 3 years for pH, total dissolved solids, and sulfates. EPA's home water testing fact sheet also points well owners with taste, odor, or staining problems toward nuisance and mineral tests such as sulfate, chloride, iron, manganese, hardness, and corrosion on a 3-year cycle. That does not make those intervals universal, but it shows why a one-size-fits-all panel rarely works for every well. (extension.umd.edu)

There is one timing rule worth remembering for families with infants. EPA says to test for nitrate in the early months of pregnancy, before bringing an infant home, and again during the first 6 months of the baby's life. (epa.gov)

Because well rules, real estate requirements, and contamination concerns can vary by state, county, and even neighborhood, confirm the right panel and any local requirements with your county health department, state drinking water or environmental office, or Cooperative Extension. (cdc.gov)

Use a state-certified lab and collect the sample carefully

A good test starts with the right lab. CDC says to use a state-certified laboratory, and EPA says only laboratories certified for drinking water testing should be used. Your local health department may offer some testing, especially for bacteria or nitrates, and many states keep lists of certified labs. (cdc.gov)

Follow the lab's instructions exactly. EPA says labs usually provide their own containers, and bacteria samples must be collected in sterile containers under sterile conditions. If you miss a holding time, fill the bottle the wrong way, or sample from the wrong tap, the result can be less useful or even unusable. For step-by-step help, see How to collect a well water sample without ruining the test. (epa.gov)

If the lab offers different panels, start with the basics and then add location-specific tests instead of ordering everything at once. That approach usually saves money and keeps the results easier to understand. Once the report comes back, use How to read a water test report: MCLs, units and flags to sort out what needs action now and what is mostly a nuisance issue. (cdc.gov)

If a result comes back positive or high

Do not panic, but do act promptly. CDC says that if test results show harmful germs or chemicals, you should consider bottled water or another safe source and contact your local health or environmental department for help understanding the result and deciding what to do next. (cdc.gov)

A positive total coliform result means your well may be vulnerable to contamination. A positive fecal coliform or E. coli result is more serious. CDC says that likely means feces, and the harmful germs in feces, have gotten into the well water. If you need help understanding that kind of result, read Coliform and E. coli in well water: what a positive result means. (cdc.gov)

After emergency disinfection, CDC says to sample for total coliform and either E. coli or fecal coliform bacteria to confirm the water is safe. If contamination was found after a disaster, CDC also recommends follow-up testing 2 to 4 weeks later and again in 3 to 4 months. If bacteria continue to show up, contact the local health department for more help. (cdc.gov)

Frequently asked questions

If my water looks and smells fine, do I still need to test it?

Yes. CDC and EPA both recommend testing private well water at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH, even when nothing seems wrong. Routine testing is how well owners catch problems early and build a record of water quality over time. (cdc.gov)

Are home test kits enough?

For decisions about drinking water safety, a state-certified laboratory is the safer choice. CDC says to use a state-certified lab, and local health or environmental departments often have lists of labs that test for bacteria, nitrate, volatile organic compounds, pH, and other contaminants. (cdc.gov)

Should I test after a flood or a well repair?

Yes. EPA and CDC both say to test after flooding, land disturbance, or when you replace or repair part of the well system. If the water smells like fuel or chemicals after an emergency, CDC says do not drink it and use bottled water until you know it is safe. (cdc.gov)

How do I know which extra tests to order in my area?

Start with your local health department, state environmental or drinking water office, or Cooperative Extension. CDC says the extra tests depend on where you live and what is happening around your well, and EPA says state or local officials can help identify common groundwater contaminants in your area, including whether PFAS testing makes sense. (cdc.gov)