How to Test Well Water: What to Order, How to Sample and How to Read the Report

Nobody tests a private well for you. The EPA puts it plainly: private well owners are responsible for delivering safe drinking water to their households, and private wells are not regulated under the Safe Drinking Water Act. Knowing how to test well water is the one skill every well owner needs, because every treatment decision on this site starts with a number from a lab report, not with a symptom.

Why and how often to test well water

The EPA and the CDC give the same baseline: test at least once a year for total coliform bacteria, nitrate, total dissolved solids (TDS) and pH. The CDC suggests sampling between April and July, when nitrate in shallow wells runs highest.

Test again, outside the annual schedule, when any of these happen:

• Flooding, land disturbance or construction near the well. Surface water over the wellhead is the classic way bacteria get in.
• Any repair to the pump, pressure tank, casing or cap. Work on the well opens it to the surface.
• A new baby, a pregnancy or someone nursing. Nitrate and manganese both have infant-specific limits, and the EPA says to test more often when small children, elderly adults or a pregnant person live in the home.
• A change in taste, odor or color. Something changed in the aquifer, the well or the plumbing.
• A notice about local groundwater, such as a state PFAS map or a county nitrate advisory.

States add longer-interval tests. The Minnesota Department of Health recommends coliform every year, nitrate every other year, arsenic and lead at least once, and manganese before a baby drinks the water. Penn State Extension adds pH, TDS and a land-use panel every three years. Your state's list is the one to follow; the county health department will have it.

Home kit or certified lab?

A kit is a screening tool. A state-certified lab is evidence.

What a kit does well. Hardness, pH and rough iron. Hardness in particular is a kit job: strips and drop kits read in grains per gallon or mg/L, and that number is all you need to size a softener (see hard well water). Hydrogen sulfide is another case where a field kit beats the lab, because the gas escapes a mailed sample within minutes (see rotten-egg smell).

What a kit cannot do. Anything with a health limit. Coliform and E. coli need a sterile bottle, an incubator and a short holding time. Nitrate strips are too coarse around the 10 mg/L limit to tell you whether an infant can drink the water. Arsenic, lead, uranium and manganese are measured in micrograms per liter. PFAS are measured in parts per trillion and can only be reported by a lab accredited for EPA Method 537.1 or 533. Penn State Extension adds a warning worth repeating: be cautious of results from any uncertified lab or from water treatment salespeople.

How to find a state-certified lab

Every state runs a drinking water laboratory certification program, and the EPA keeps a directory of them: Contact Information for Certification Programs and Certified Laboratories for Drinking Water. Pick your state, open its list and look for labs that accept samples from private homeowners; many serve only public water systems.

Three shortcuts: call the county health department, which often sells coliform and nitrate kits at the counter; check your state university's extension office, several of which run certified mail-in labs such as Penn State's Agricultural Analytical Services Laboratory; and compare prices, which the Minnesota Department of Health specifically recommends because the same panel varies widely between labs. Get the bottles from the lab you use; it will reject a sample taken in the wrong container.

What to order

The basic panel. Total coliform, E. coli, nitrate as nitrogen, pH, TDS, hardness, iron and manganese. The first four are the annual set; the last four are what you need to choose and size treatment, since iron filters are rated by mg/L of iron, softeners by hardness and iron together, and manganese has its own limit. Most labs sell this as a package.

Add-ons by situation. Penn State Extension matches tests to the land use within sight of the house, and the pattern holds anywhere:

The granite row deserves a note. Radon in water comes from the radioactive breakdown of uranium in the ground, and the EPA recommends testing well water for it even though it does not regulate private wells. Arsenic is lab-only with a 0.010 mg/L limit; the Minnesota Department of Health reports it was detected in about 40 percent of new wells drilled there since 2008, with about 10 percent of private wells over the limit.

How to sample correctly

A bad sample is worse than none, because it produces a number you will act on. These steps follow the Illinois Department of Public Health coliform and nitrate instructions and match what most state labs require.

1. Sample ahead of any treatment. Use the cold tap nearest the pressure tank or an outside spigot on the raw line, so the lab sees the well and not your softener. The exception is lead or copper, taken at the kitchen tap after the water has sat at least 12 hours (a first-draw sample), because the plumbing is what you are testing.
2. No hose, swing-spout or dirty tap. Remove the aerator.
3. Flush. Run at full flow until the pump kicks on and runs several minutes, so you draw fresh groundwater rather than tank water.
4. Reduce to a pencil-sized stream before filling.
5. Fill without touching. Do not rinse the bottle, do not touch the inside of the cap or the rim, fill to the line and cap it immediately.
6. Fill out the form with date, time and sampling point; the lab enforces holding times from it.
7. Keep it cold and move fast. Illinois discards bacteria samples received more than 30 hours after collection. Ask the lab which days it accepts them before you collect.

For PFAS, follow the lab's stricter instructions exactly; a sample is easy to contaminate from your own hands or clothing.

How to read the report

Units. Labs report mass per liter, and the parts-per units are the same thing under other names. Penn State Extension spells it out: mg/L is parts per million (ppm), µg/L is parts per billion (ppb), ng/L is parts per trillion (ppt), each a factor of 1,000. Iron and nitrate come in mg/L, arsenic and uranium in µg/L, PFAS in ng/L. Check the unit before comparing a result to a limit.

MCL, SMCL and advisory. A Maximum Contaminant Level (MCL) is a health-based, enforceable limit for public systems. A Secondary Maximum Contaminant Level (SMCL) is a non-enforceable guideline for taste, odor, color and staining. A health advisory is a non-regulatory number for a contaminant with no MCL, such as manganese. None is enforced on a private well, but MCLs are the right benchmark for health and SMCLs for nuisance problems.

Nitrate as N versus as NO3. The 10 mg/L limit is nitrate-nitrogen. A lab reporting nitrate as NO3 shows a number 4.4 times higher against a 45 mg/L limit. Match the form to the limit.

The PFAS limits are the April 2024 rule; in May 2026 the EPA proposed keeping the PFOA and PFOS limits while extending the compliance deadline, and separately proposed rescinding the limits for PFHxS, PFNA and GenX. Neither proposal was final as of October 2026.

What to do with the results

• Coliform or E. coli positive: stop drinking the water or boil it, inspect the cap and casing, shock chlorinate, and retest a week or more after disinfection; consider UV if it comes back. See bacteria in well water.
• Nitrate over 10 mg/L: reverse osmosis or ion exchange at the kitchen tap; carbon and softeners do nothing for it. See nitrates.
• Iron over 0.3 mg/L: an air-injection or catalytic media filter sized by the mg/L and pH. See iron.
• Manganese over 0.05 mg/L, and especially over 0.3 mg/L with an infant in the house: catalytic media filter. See manganese.
• Hardness over about 7 gpg (120 mg/L): an ion-exchange softener, after iron is handled. See hardness.
• Rotten-egg odor: find out whether it is the heater or the well, then aeration or catalytic carbon. See sulfur.
• Cloudy water or grit: a spin-down or cartridge filter, always first in line. See sediment.
• PFAS detected: certified carbon or RO with a PFOA/PFOS claim on the certificate. See PFAS.
• Yellow water that passes the jar test for iron: tannin resin. See tannins.

Then the best well water filtration systems page ranks systems by the problem they solve, the sizing tool turns your numbers into a tank size and flow rate, and the installer directory lists local contractors if you would rather hand the report to someone who installs these every week. After any treatment is installed, retest the treated water; only a second lab test tells you it is working in your house.

What testing costs

Prices vary by state, panel and county subsidy, so get a current quote. As a reference, Penn State's certified lab lists (read 2026-10-05) a standard package of coliform, E. coli, pH and TDS at $60, an agriculture/septic package adding nitrate-nitrogen at $70, an aesthetics package adding hardness, alkalinity, corrosivity, copper, iron and manganese at $85, a trace-metals package including arsenic and lead at $130, and an extensive package at $220. HomeAdvisor's water treatment cost guide (read 2026-10-05) puts water testing at $30 to $500 across the range from a single bacteria test to a broad scan; PFAS by a certified method sits at the upper end. The test is the cheapest part of the job and the only part you cannot skip.