How often to test well water

EPA says to test a private well every year for bacteria, nitrate, total dissolved solids, and pH. Some states add arsenic, lead, radon, and uranium every few years.

Every year

• EPA: "Test your private well annually for total coliform bacteria, nitrates, total dissolved solids, and pH levels." (EPA)
• Maine: "Well owners should test their private drinking water annually for coliform bacteria, E. coli, and nitrates and nitrites." (Maine CDC)
• Wisconsin: "Bacteria and nitrate at least once a year." (Wisconsin DHS)

Test sooner when

EPA lists these (EPA):

• "Conditions near your well have changed significantly (i.e. flooding, land disturbances, and new construction or industrial activity)" (after a flood)
• "You notice a change in your water quality (i.e. odor, color, taste)."
• "You may want to test more frequently if small children or elderly adults live in your house or if someone in your house is pregnant or nursing."

Maine adds: "If you are expecting a baby" (Maine CDC).

Every few years

• Maine: "It is also recommended that well owners test their water every 3-5 years for arsenic chloride copper fluoride hardness iron lead magnesium manganese pH radon sodium uranium" (Maine CDC)
• Wisconsin: "Arsenic and lead at least once every five years." (Wisconsin DHS)
• Minnesota: "Test your well for arsenic at least one time beyond the initial well water test when the well is first constructed." (MDH)

Your own state may say something different. Your state page lists its lab.

Get it done

Find a well test near you · What a well test costs · Check your results

Sources checked October 2, 2026.