How Often Should You Test Well Water? Annual, After Floods, Before Buying

On this page

1. Every year
2. Every few years
3. Test right away if…
4. After a flood
5. During pregnancy and with an infant
6. Before buying (or selling) a home with a well
7. A simple testing calendar
8. Where to send samples
9. Sources

Every year

CDC and EPA agree on an annual baseline:

• Total coliform bacteria
• Nitrates
• Total dissolved solids (TDS)
• pH

CDC also recommends checking your well for mechanical problems every spring.

Timing tip: EPA’s home testing fact sheet says nitrate testing is best done in spring or summer after a rainy period.

Every few years

If you have taste, odor or staining problems, EPA’s fact sheet suggests testing for sulfate, chloride, iron, manganese, hardness and corrosion every three years.

For natural contaminants like arsenic and uranium, ask your health department how often to recheck. Connecticut, for example, notes that uranium levels can vary seasonally and recommends retesting any result above 10 µg/L.

Test right away if…

From CDC and EPA:

• You’re told about well water problems in your area
• Flooding, land disturbance or a waste-disposal site affects the area near your well
• You replace or repair any part of the well system
• The water’s taste, color or smell changes
• Someone in the home becomes pregnant, or a child starts living with you
• Someone in the household has recurring stomach or intestinal illness (test for coliform)

EPA adds that households with small children, elderly adults, or someone pregnant or nursing may want to test more often than once a year.

After a flood

If floodwater reached your wellhead, don’t drink the water until it’s been tested. Here’s what CDC says to do after an emergency (CDC):

• Use bottled water until you’re sure the water is safe.
• Contact your local or state health department for advice. CDC recommends having a well or pump contractor disinfect the well.
• Wait at least 7–10 days after disinfection before sampling. You can’t sample until all the chlorine has been flushed out.
• Test for total coliform and E. coli or fecal coliform.
• If the result is clean, follow up with another test in 2–4 weeks and another in 3–4 months. After that, check bacteria at least twice a year.

Disinfection steps: How to Shock Chlorinate a Well, Step by Step

During pregnancy and with an infant

Nitrate is the key test. EPA’s fact sheet recommends testing for nitrate early in pregnancy, before bringing an infant home, and again during the baby’s first six months. Nitrates in Well Water: Health Risks, Limits and Fixes

Before buying (or selling) a home with a well

A home inspection doesn’t automatically include a water test, so ask for one. Some states require it. Under New Jersey’s Private Well Testing Act, sellers or buyers must test untreated well water for up to 43 parameters, and both parties must review the results before closing. NJ landlords must also retest every five years. The required parameters include total coliform, nitrate, iron, manganese, pH, VOCs, lead, arsenic, gross alpha, and (since December 2021) PFOA, PFOS and PFNA (NJ rule text).

Even if your state has no such rule, the New Jersey list is a solid model for a pre-purchase panel. Add whatever your county health department flags locally. What to Test Your Well Water For (and What You Can Skip)

A simple testing calendar

Where to send samples

“For health and safety decisions, use a state-certified lab or your health department’s testing program. For additional screening, you can also use a mail-in lab kit such as Tap Score: Essential well water test →.” Find certified labs through EPA’s state directory. Tap Score vs Your State-Certified Lab vs DIY Strips

Related: Buying a home? Use our checklist for buying a house with a well.