How often should you test well water?
Updated July 2026
Test a private well at least once a year for coliform bacteria, nitrates, and pH, and run a fuller panel that includes metals and locally common contaminants every 3 years. Unlike a municipal supply, a private well has no one testing it but you, so problems from a nearby septic system, farm runoff, or naturally occurring arsenic can sit in your glass undetected. A basic bacteria-and-nitrate test runs $50–150, which is a small price for water your household drinks every day.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Annual baseline screen | Every year | Coliform bacteria, nitrates, and pH catch the most common well problems cheaply |
| Comprehensive panel | Every 3 years | Adds arsenic, lead, other metals, and contaminants common in your area |
| After a flood reached the wellhead | Test now | Surface water and runoff can push bacteria straight into the well |
| After pump, casing, or plumbing work | Test now | Repairs can introduce bacteria; many wells are shocked and then retested |
| New taste, smell, or color | Test now | Sudden sulfur, metallic, or cloudy water signals a real change worth catching |
| Infant, pregnancy, or immune-compromised at home | Nitrates yearly, no exceptions | Nitrate above 10 mg/L is dangerous to infants and warrants close watch |
| Near farms, septic, or fuel tanks | Add local contaminants | Nitrates, pesticides, or fuel can migrate through soil into groundwater |
The cost of skipping it
What skipping it costs: with a private well, you are the water utility, and no agency will warn you. Coliform bacteria signal a path for E. coli and other pathogens that cause days of gastrointestinal illness, nitrate above the EPA limit of 10 mg/L endangers infants, and long-term arsenic exposure has serious health effects, all with no taste or smell. A basic test is $50–150 and a full panel $150–600, versus the health toll of drinking bad water or the cost of a whole-house treatment system installed after the fact.
How to do it (Collect in 15 minutes · lab-analyzed)
- Contact your county health department or a state-certified lab; many mail out a sample kit with instructions.
- Follow the collection steps exactly: use the sterile bottle provided, do not rinse it, and do not touch the rim.
- Sample from a tap ahead of any softener or filter for a true reading of the source water.
- Ship the sample the same day, kept cold, so the bacteria results stay valid.
- Compare results to EPA limits: coliform should be absent and nitrate below 10 mg/L.
- If a test fails, shock chlorinate or add treatment, then retest to confirm the water is clean.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing well water tests schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
What should I test my well water for?
Every year, test the basics: coliform bacteria, nitrates, and pH. Every 3 years, step up to a comprehensive panel that adds metals like arsenic and lead plus contaminants common to your region. Layer in extra tests based on your surroundings: nitrates and pesticides near farmland, fuel components near underground tanks, or radon in water in certain geologies. Your county health department can tell you which local contaminants are worth including so you are not paying for tests that do not apply.
How much does well water testing cost?
A basic bacteria-and-nitrate screen typically runs $50–150, while a comprehensive panel covering metals and a broad contaminant list is closer to $150–600 depending on how many analytes are included. Many county health departments offer low-cost or subsidized bacteria testing, and some state labs price a la carte so you only pay for what you need. Spread across a household that drinks the water daily, even the yearly basic test lands at a few dollars a week.
My well water tastes fine, so do I still need to test it?
Yes. The most dangerous well contaminants give no warning at the tap: coliform bacteria, nitrate, arsenic, and radon are all invisible and tasteless. Taste and smell only flag a subset of issues, like sulfur or iron, and often only once they are severe. Clear, good-tasting water can still carry bacteria from a compromised well cap or nitrate from a nearby field. The annual test exists precisely because your senses cannot detect the things most worth catching.
What do I do if my well fails a bacteria test?
Stop drinking it untreated and boil water for consumption until it is resolved. Then shock chlorinate the well to disinfect it, and fix the likely entry point: a cracked casing, a missing or loose well cap, or a septic system too close. Retest one to two weeks after shocking to confirm the bacteria are gone. If tests keep coming back positive, the source is still open, and a continuous UV or chlorination system is the durable fix.