Water From a Private Well
Nobody tests a private well but its owner. What to test every year, when to test sooner, and what to do with the answer.
If your water comes from your own well, there is no utility behind it and no annual report about it. EPA is explicit on both points: water from private domestic wells is not regulated under the Safe Drinking Water Act, nor by most state governments, and private well owners are responsible for the safety of the water they deliver to their households.
That is not a small group. EPA estimates that more than 23 million US households rely on a private well for drinking water. What they have in common is that every check a public supply runs on their behalf, they have to arrange for themselves.
The difficulty is that the problems worth finding are mostly invisible. Bacteria and nitrate have no taste, colour or smell, so a well that has tasted the same for twenty years tells you nothing about either. Testing is the only way to know, and the schedule below is the one EPA and CDC both give.
What to test every year
EPA and CDC give the same baseline: test a private well at least once a year for total coliform bacteria, nitrate, total dissolved solids and pH. CDC adds any other germs or chemicals of concern in your area, which your county or state health department will know.
Each of the four earns its place differently. Coliform bacteria are an indicator: their presence means there is a path from the surface into your water, through a cracked cap, a failed seal or flooding. Nitrate is a health limit set to protect infants, and it is the classic contaminant of wells near farmland. Total dissolved solids and pH are the baseline that tells you whether the water is changing from one year to the next, and whether it is corrosive enough to pick up metal from your plumbing.
Coliform and nitrate are the two to send to a certified laboratory. A home kit can tell you whether to call one; the laboratory result is the one to act on.
When to test sooner
Once a year is the floor. EPA says to test right away if there are known problems with groundwater or drinking water in your area; if conditions near your well have changed significantly, such as flooding, land disturbance, or new construction or industrial activity; if you replace or repair any part of the well system; or if you notice a change in the water's odour, colour or taste.
CDC adds two more that are about the household rather than the well: when someone in the home becomes pregnant, and when a child comes to live with you. The nitrate limit exists to protect infants, which is why those two are on the list.
What you notice also says what to test for. EPA pairs stained fixtures and laundry with iron, copper and manganese; an objectionable taste or smell with hydrogen sulfide, corrosion and metals; scaly residue and soap that will not lather with hardness; and a salty taste, or a heavily salted road nearby, with chloride, total dissolved solids and sodium.
Look at the well, not just the water
EPA also asks well owners to inspect the exposed parts of the well from time to time, looking for a cracked, corroded or damaged casing, a broken or missing cap, and settling or cracking around the surface seal. These are the openings bacteria come through.
That is why a positive coliform result is never answered with a filter. The question it raises is how the outside got in, and the answer is in the well itself, which a licensed well contractor or your health department can help you find.
Keep your well's record here
Answer a few questions and get a plan for your well: what to test first, how, and why. Save it and we will remind you when the annual test is due, and close the reminder ourselves when you log the results.
Start my well's planThe numbers that decide it
Common questions
How often should I test my well?
At least once a year for total coliform bacteria, nitrate, total dissolved solids and pH, according to both EPA and CDC — and right away after flooding, a repair to the well, or a change in how the water looks, smells or tastes.
Who tests well water?
A state-certified drinking water laboratory. EPA keeps a list of certification contacts by state, and your county or state health department can usually point you to a laboratory and tell you which local contaminants to add to the panel.
Can I use a home test kit instead?
For a first look, yes, and some kits are reasonable screens. For bacteria and nitrate, though, treat a home result as a reason to call a laboratory rather than as the answer: those two are the results to act on, and the ones to have in hand before an infant drinks the water.
My well water has always tasted fine. Do I still need to test?
Yes. Taste and smell are useful warnings about some problems, but bacteria and nitrate have neither, and EPA's own words are that odour-free water is not necessarily safe to drink.
Sources
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice.