Private wells are not regulated the way public supplies are. No agency samples them and no report arrives. The testing regime is whatever the household decides to do.
Annually, at minimum
Total coliform and E. coli. The indicator organisms for whether surface contamination is reaching the well. A positive result means the well or its seal needs attention, and it is the single most important test.
Nitrate. Elevated nitrate is a serious hazard for infants and it is common in agricultural areas and near septic systems. It is odourless and tasteless.
Also test after any work on the well, after flooding, after any change in taste, smell or appearance, and if anyone in the household becomes repeatedly unwell.
Every few years, or once and then as circumstances change
Hardness, iron and manganese, which determine treatment.
pH, which affects corrosion and how treatment behaves.
Total dissolved solids and sulphate.
Lead and copper, sampled first-draw from the tap, since these come from the plumbing rather than the source.
Arsenic, radon, uranium, fluoride — depending on the geology. The state or county health department publishes what is a known concern locally, and that guidance is the right basis for what to include.
Pesticides or volatile organics, where land use or a nearby site makes them plausible.
How to collect a sample
Use the laboratory's bottles and follow their instructions exactly.
The bacterial sample in particular is easy to contaminate — a dirty tap, a hand on the bottle rim, an aerator harbouring growth. A false positive produces an unnecessary alarm and a repeat test.
Sample from a cold tap ahead of any treatment for a source assessment, and from the kitchen tap for a lead and copper first-draw sample.
Deliver promptly and refrigerated where instructed, since holding times matter for bacterial samples.
Reading the result
The report gives measured values against limits.
Above a health-based limit — a treatment requirement, and for bacteria an immediate one.
Above a secondary or aesthetic limit — iron, manganese, hardness, sulphate — a nuisance rather than a hazard, and what determines the treatment equipment.
Non-detect is not the same as zero; it means below the method's reporting limit.
If bacteria are present
Retest first, since collection contamination is common.
Confirmed, the well needs investigating: the cap, the casing seal, the grouting, the surface grading around it, and the separation from any septic system.
Shock chlorination treats the water in the well and does not fix the reason it got in. A well that repeatedly tests positive has a construction or a siting problem, and continuous disinfection is a management rather than a cure.
Use an alternative supply until it is resolved.
What treatment does not cover
A softener removes hardness. An iron filter removes iron. Neither disinfects, and neither addresses nitrate, arsenic or organics.
Matching the treatment to the test result — rather than to the symptom that prompted the call — is what keeps a treatment budget rational.
Keeping the record
Every result, dated, with the laboratory's report.
A series of tests over years shows whether anything is trending, which a single result cannot. It is also what a buyer will ask for, and on a rural property a folder of annual results is a genuine asset at sale.
Cost
State-certified laboratories offer well-owner packages at a modest price, and many county health departments subsidise or run testing programmes.
The annual bacteria and nitrate test is a small sum. A full panel every few years is larger and still minor against the cost of treating the wrong thing, or of not knowing about something that matters.