Private well testing: what to test, and when

Public water systems have to test their water constantly and report what they find. Private wells don’t. According to USGS, their water quality isn’t regulated by the Safe Drinking Water Act or, in most cases, by state law, so the people who drink from them are the ones responsible for testing.

Most of what USGS found above health benchmarks came from nature, not industry: metals and radioactive elements from the rock, plus nitrate. That’s why even a well far from any factory needs testing. Some states and counties have their own well rules, so check with your local health department too.

CDC and EPA agree on the baseline: test at least once a year for four things.

• Total coliform bacteria. Not usually a germ that makes people sick, but an indicator that something may be giving contamination a way into the water.
• Nitrate. From fertilizer, manure, and septic systems. It’s most dangerous for infants under six months, and levels are typically highest between April and July, so EPA suggests testing then.
• Total dissolved solids (TDS). A broad measure of everything dissolved in the water. A jump from one year to the next is a reason to look closer.
• pH. How acidic the water is. Acidic water can corrode plumbing, which is one reason EPA pairs corrosion with lead testing.

CDC also suggests checking the well itself every spring for mechanical problems: the cap, the casing, and the seal around it.

Beyond the basics, what to test depends on what’s around you. EPA publishes a table of conditions and the tests each one calls for. Check whatever applies to your well, and take the list to your lab and health department.

Don’t wait for the yearly test if any of these happen. They come from CDC’s and EPA’s guidance:

• You hear about problems with groundwater or drinking water in your area.
• Conditions near the well change: flooding, land disturbance, new construction, or new industry.
• You repair or replace any part of the well system.
• The water’s taste, color, or smell changes.
• Someone in the home becomes pregnant, or a baby or child moves in.
• People in the household keep getting stomach illnesses.

A result is only as good as the lab and the sample. Use a lab that’s certified to test drinking water. Your state’s lab certification program, your local or state health department, or your county can give you a list, and some health departments test private wells for free.

Ask the lab for its bottles and instructions, and follow them exactly. They’ll tell you where to take the sample, how to handle the bottle, and how quickly it has to get back to them, which matters most for bacteria. Questions about your well itself? The National Ground Water Association runs a Private Well Owner Hotline at 855-420-9355.

Your lab report will list each result and its units, and it may compare them with EPA’s drinking water standards. Those standards apply to public water, not private wells, but USGS calls them useful benchmarks, and they’re the yardstick your health department will use too. Some are health limits; others are goals for taste, odor, and appearance:

1. Switch to a safe source for drinking and cooking if bacteria or nitrate are the problem, like bottled water. For infant formula, don’t use well water above 10 mg/L nitrate, and don’t use untested well water at all.
2. Call your local health department. EPA’s advice is to get specific steps from them and retest to confirm the result before you spend money.
3. Don’t boil it unless the problem is germs. Boiling kills microbes, but it doesn’t remove nitrate, lead, or PFAS, and it can concentrate them as water boils off.
4. Match any treatment to the contaminant. Disinfection handles bacteria; other problems need filtration, distillation, or other treatment certified for that contaminant. Sometimes the answer is a new source or a new well. For lead and PFAS, see choosing a certified filter and what works for PFAS.
5. Retest after any fix, and keep your results together, so you can spot a trend from year to year.

And protect the well from here on. EPA’s list: slope the ground so runoff drains away from the well, keep a sealed cap on it, inspect the casing and seals for cracks, keep fuel, fertilizer, and chemicals away from it, pump the septic system as often as your health department recommends, and hire a certified driller for any new well, repair, or closure.