Water quality recommendations on this page are informational. Test results vary by location. Contact your state health department or a certified lab for guidance specific to your water supply.
WELL WATER TESTING
How Often Should You Test Well Water?
There is no single answer. Bacteria changes fast. Arsenic changes slowly. PFAS sits somewhere in between. Here is the schedule that most state health departments and the CDC recommend for private well owners.
Last reviewed: May 2026
Recommended testing frequency
| Contaminant | Recommended frequency | Notes |
|---|---|---|
| Bacteria / coliform | Every year | More often after heavy rain or nearby animal activity |
| Nitrates | Every year | Especially if near agriculture or septic systems |
| pH and hardness | Every 3 years | Changes slowly. Affects plumbing and filter performance. |
| PFAS | Every 3 years (now) | Annual if near industrial sites, military bases, or airports |
| Arsenic | Every 5 years | Geological, stable. More frequent in known high-arsenic regions. |
| Lead | Once + after plumbing work | Plumbing concern, not groundwater. Test after any major pipe work. |
| Full panel | Every 3 to 5 years | On new home purchase, after flooding, after nearby land use change |
When to test more often
The schedule above is a baseline. These five situations call for unscheduled testing:
After flooding
Floodwater can carry bacteria, nitrates, and surface contaminants into a wellhead. If your property floods, test for bacteria before resuming normal use.
After septic system work
Septic repairs or replacement disturbs the ground near the well. Bacteria can migrate more easily in the weeks following work. Test 30 days after completion.
New agricultural activity nearby
A new farm, a change in crop type, or new pesticide use within a mile of your well can affect groundwater. Test for nitrates and pesticides if you see significant new activity.
PFAS news in your area
Local news or state agency notices about PFAS contamination near you are a signal to test. PFAS plumes can migrate slowly through groundwater for years after the source is removed.
New neighbor with a septic system
A failing septic system on a neighboring property can affect your well. Bacterial counts and nitrates are the main concerns.
How to track and store your results
Keep a folder (paper or digital) for every test result. Store the date, the lab, the contaminants tested, and each measured level. When you retest, compare the new result to the previous one.
A single high reading is worth investigating. A pattern of rising levels is a signal to act. Two results from the same lab make comparisons more reliable than switching labs each year.
If you sell your property, share the testing history with buyers. It adds value and avoids future disputes about the condition of the water supply.
Set an annual reminder
The easiest way to stay on schedule is to tie annual testing to a date you already remember. Many well owners test in spring, when groundwater levels change and bacteria risk rises after winter snow melt.
Set a calendar reminder now. Or sign up for testing reminders:
Free testing reminder
We send a free annual email reminder when it is time to retest. No spam, no sales pitch. Just the reminder.
Sign up for free remindersFrequently asked questions
How often should I test my well for bacteria?
Every year at minimum. Bacteria levels can change quickly after heavy rain, flooding, or nearby animal activity. If you notice any change in taste, smell, or water clarity, test immediately without waiting for the annual cycle.
Do I need to test for PFAS every year?
Every three years is the current recommendation for private wells not near known contamination. If you are within 10 miles of a military base, airport, or industrial site, test annually. After the EPA 2027 reporting deadline brings new public data, you may need to reassess.
When should I get a full water panel?
When you first move into a property with a private well. After any major change in nearby land use, like a new farm operation or industrial facility. After any flooding that may have reached the wellhead. And every 3 to 5 years for routine maintenance.
What counts as a passing well water test?
No legal standard applies to private wells. But the EPA maximum contaminant levels for public water give you a useful benchmark. Zero detectable coliform bacteria, nitrates below 10 mg/L, and PFAS below 4 ppt are the targets to aim for.