What should well water be tested for every year?

The consensus annual minimum is total coliform bacteria and E. coli, plus nitrate, with a look at anything that changed: taste, odor, color, or nearby land use.

How much does well water testing cost?

Basic bacteria and nitrate panels through state-certified labs and county health departments commonly run modest lab fees, with broader chemical panels scaling up from there. Many counties subsidize the basics.

Who regulates private well water?

Practically, nobody. Public systems are federally regulated; a private well's quality is entirely the owner's responsibility, which is the whole argument for a testing habit.

How do I take a proper water sample?

Use the lab's sterile bottle, sample from an inside tap with the aerator removed, flame or sanitize the spout, run the water several minutes first, and keep the sample cold and prompt. Bacteria results are only as good as the sampling.

Well Water Testing: What to Test For and When

Page last reviewed: August 2026 · Reviewed by Harold R. Bennett, retired home inspector

Well water testing is the private well owner’s substitute for the entire regulatory apparatus that watches municipal water, because no one tests a private well unless its owner does. A well can look, taste, and pour perfectly while carrying bacteria, nitrate, or arsenic, all invisible, all testable for modest lab fees. This reference lays out the schedule: what to test annually, what to test occasionally, and what events trigger an immediate sample.

The annual minimum

Two tests, every year, ideally in spring or after wet season when contamination pressure peaks:

Total coliform and E. coli. Coliform bacteria are the canary panel: mostly harmless themselves, their presence means surface water or soil is reaching the well, a pathway other organisms can share. E. coli specifically signals fecal contamination and moves the result from “investigate” to “act.” A positive coliform result typically means resampling, inspecting the wellhead (a cracked cap, failed grout seal, or ponding at the casing are the usual suspects), shock chlorinating, and retesting until clean.

Nitrate. Sourced from fertilizer, septic systems, and animal operations, nitrate matters most acutely for infants, and it drifts with land use, which is why it earns annual status rather than occasional.

The every-few-years panel

Every 3 to 5 years, or once thoroughly when you first take ownership of a well, widen the lens:

The workhorse chemistry: pH and corrosivity (aggressive water eats plumbing and fixtures), hardness (the number that schedules your water heater’s whole life), iron and manganese (the staining economy), sulfate, chloride, and total dissolved solids.

The regional serious ones: arsenic, radon in water, and uranium occur naturally in the geology of large swaths of the country and correlate with nothing you can taste; your county health department or state geological survey knows whether your area is implicated, and one lifetime test answers the question. Lead deserves a first-draw test in any house with pre-1990 plumbing, a supply-side companion to the fixture concerns every older house carries.

Situational additions: volatile organics near fuel storage or industry, pesticides in intensive agriculture, PFAS where local advisories suggest it.

Event-triggered testing

Some samples should not wait for the calendar: any change in taste, odor, or color (with the sulfur smell and staining diagnostics as first-pass guides to what changed); after flooding or ponding at the wellhead; after any well or pump service that opened the system, once the post-work chlorination clears; a new infant or immune-compromised household member (nitrate and bacteria); a neighbor’s contamination finding, since aquifers ignore property lines; nearby drilling, blasting, or land-use change; and at purchase of any property with a well, where a full panel is cheap diligence against an unknown history.

Sampling and reading results

Use a state-certified drinking water lab, county health department, or extension service, and follow their sampling ritual exactly: the sterile bottle, an indoor tap with aerator removed, a sanitized spout, several minutes of flushing (except deliberate first-draw lead samples), cold transport, prompt delivery. Half of all scary bacteria results are sampling artifacts, and the protocol is what makes the other half believable.

Results arrive against two kinds of benchmarks: health-based limits (bacteria, nitrate, arsenic, lead), where exceedances warrant action, alternate water for the vulnerable use in the meantime, and treatment or well work as indicated; and aesthetic guidelines (hardness, iron, sulfate, TDS), where the number simply prices the nuisance and sizes the treatment decision. Keep every report in one folder: trends across years tell you things single results cannot, and the file transfers with the house as quiet evidence of a well-run well.

The bottom line

Bacteria and nitrate every year, the broad panel every few, the regional heavy hitters once, and a fresh sample whenever the water or the circumstances change. The lab fees are the entire cost of being your own water utility’s regulator, and the folder of clean results is what a well is supposed to produce along with the water.