Private Well Testing: What to Test For and When (2026 Checklist)
43 million Americans on wells with zero EPA protection. Your testing checklist.
43 million Americans on wells with zero EPA protection. Your testing checklist.
Test your well annually for bacteria, nitrate, and pH at minimum — and add PFAS, arsenic, and radon testing if you are near industrial sites, farms, or granite bedrock.
Annual Tests
Private well owners should test their water at least once per year for total coliform bacteria, nitrate, pH, and total dissolved solids. These four parameters catch the most common well water problems: bacterial contamination from surface runoff, agricultural nitrate infiltration, and changes in water chemistry that signal something has shifted in your aquifer or well casing.
Coliform bacteria is the top priority. A positive coliform test does not necessarily mean dangerous pathogens are present, but it indicates that surface contamination is reaching your well. Follow up a positive coliform test with an E. coli test immediately. If E. coli is detected, stop drinking the water and shock chlorinate the well.
Nitrate is especially critical if infants, pregnant women, or livestock drink from the well. Nitrate above 10 mg/L can cause blue baby syndrome. Wells near agricultural fields, feedlots, or septic systems are at highest risk. Spring testing, after snowmelt and heavy rains, typically catches peak nitrate levels.
Annual testing costs $50-150 through your state or county health department, which often offers subsidized well water testing programs. Some states provide free bacterial testing. Contact your local health department to find out what programs are available in your area.
One-Time
Beyond the annual basics, every well should be tested once for contaminants that do not change frequently but are important to know about. These one-time tests establish your baseline and determine whether you need treatment systems.
Arsenic: Naturally occurring in bedrock across many US regions, especially the Southwest, New England, and parts of the Midwest. The EPA limit is 10 PPB, but health researchers recommend action at lower levels. Arsenic is tasteless and odorless, so testing is the only way to know.
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Radon: Dissolved radon in well water releases radon gas into your home's air when you shower or run water. If your area has elevated radon in air (check the EPA radon zone map), test your well water too. Aeration systems or granular activated carbon filters can reduce waterborne radon.
PFAS, lead, and hardness round out the one-time panel. PFAS can reach wells near industrial sites, military bases, or areas where firefighting foam was used. Lead comes from well pumps, fittings, or plumbing, not from the groundwater itself. Hardness affects your appliances and plumbing and determines whether you need a softener.
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When to Retest
Outside of your annual testing schedule, certain events should trigger an immediate retest of your well water:
After flooding or heavy storms: Floodwater can overwhelm well casings and introduce surface bacteria, pesticides, and sediment directly into your water supply. Test for coliform and E. coli within a week of any flood event. If the casing was submerged, shock chlorinate the well and retest before resuming use.
After any well work or pump replacement: Disturbing the well can introduce bacteria or stir up sediment. Run the well for several hours after work is completed, then test for bacteria before drinking the water.
When you notice changes: Any sudden change in taste, color, smell, or clarity warrants testing. Brown or rusty water may indicate iron bacteria or a failing well casing. Rotten egg smell (hydrogen sulfide) suggests sulfate-reducing bacteria. A sudden salty taste could mean road salt or seawater intrusion depending on your location.
When nearby land use changes: New construction, a neighbor installing a septic system, new agricultural activity, or industrial development within a half-mile of your well can affect groundwater quality. Test within 3-6 months of any significant land use change nearby.
Labs
For well water, lab testing is not optional. DIY test strips can give you a quick read on hardness, pH, and iron, but they lack the precision needed for health-critical contaminants like bacteria, arsenic, and PFAS. Always use a certified lab for your annual and baseline testing.
State and county health departments are often the most affordable option. Many offer well water testing packages for $50-100 that cover bacteria, nitrate, and basic chemistry. Some states provide free coliform testing. Call your county health department and ask what well testing services they provide.
Mail-in lab kits like SimpleLab Tap Score are convenient if your local health department does not offer comprehensive testing. They mail you collection vials, you collect samples following their instructions, ship them back, and receive a detailed report in 7-14 days. The well water-specific kit ($200-300) covers bacteria, metals, minerals, and common well contaminants in a single panel.
For PFAS testing, you need a specialized test. Standard water panels do not include PFAS. The Tap Score PFAS test covers 14+ PFAS compounds including PFOA and PFOS. This is worth doing once, especially if your well is within 5 miles of a military base, airport, or industrial facility where firefighting foam was used.