Testing water wells runs on two clocks: a routine annual check for bacteria and nitrate, and event-driven retests whenever something changes, a flood, a repair, a new taste or stain, a nearby land-use change. Both clocks are the owner's to keep, because the EPA notes private wells are not federally regulated under the Safe Drinking Water Act: nobody schedules this test except you.
The routine clock: what gets checked every year
Health departments and state well programs commonly recommend an annual check of total coliform bacteria and nitrate, the two findings that matter most and change fastest, with pH and total dissolved solids as cheap additions that reveal trends. A fuller panel covering metals, hardness and local suspects is worth running at wider intervals or whenever the annual results drift. The scale of what routine testing catches is real: a USGS study of 2,100 private wells found about one in five carried at least one contaminant above a human-health benchmark.
The event clock: things that force an immediate retest
Retest outside the schedule whenever the well is worked on, after the wellhead floods or standing water covers it, after nearby drilling, blasting, construction or a change in adjacent farmland, when a household member is pregnant or a new baby arrives (nitrate matters most to infants), and at any change in taste, odor, color or staining. Also test before buying a home with a well and after any period the property stood vacant. Event tests answer a different question than routine ones: not how is the well trending, but did this specific thing hurt it.
Keep the results: the record is the asset
A single test describes a day; a file of tests describes the well. Keep every lab report together and compare year over year: a slow rise in nitrate or TDS is visible in a record and invisible in a one-off. The record also pays at sale time, since buyers and lenders increasingly ask for well history, and it lets a treatment installer size equipment from a trend rather than a snapshot. When sampling day comes around, our well water testing directory lists local labs and services that pull samples correctly, which is half of what makes results comparable across years.
Questions people ask about testing water wells
What should be tested every year on a private well?
Total coliform bacteria and nitrate at minimum, since both can change quickly and both matter to health. Adding pH and total dissolved solids costs little and makes the year-over-year record far more informative.
When during the year is the best time to test a well?
Many owners test in spring or after the wettest season, when surface influence on the aquifer peaks and problems are most likely to show. Consistency matters as much as timing: testing the same season each year makes results comparable.
Should I test after having well work done?
Yes, always. Any opening of the system can introduce bacteria, and post-repair disinfection needs verification. Sample after the work is complete and any shock chlorination has fully flushed from the lines.