How to Test Well Water

Test a private well at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH, the EPA and CDC both say. Use a state-certified laboratory and its sterile bottle, and deliver a bacteria sample fast: published limits run from 6 to 48 hours.

Nobody tests a private well for you. The EPA says private wells are not regulated by the EPA or required to follow its standards, and that private well owners are responsible for delivering safe drinking water to their households.

The table lists what to test for and how often. Where sources differ, each is named.

What to test well water for, and how often

Test	How often	Source
Total coliform bacteria	Every year	EPA, CDC, National Ground Water Association, Minnesota Department of Health
Nitrate	Every year	EPA, CDC, National Ground Water Association, Minnesota Department of Health
Total dissolved solids and pH	Every year (EPA, CDC); every three years (Penn State Extension)	EPA, CDC, Penn State Extension
Arsenic, lead and manganese	At least once	Minnesota Department of Health
Nitrate, when a baby is expected	Early in the pregnancy, before bringing the infant home, and again in the baby's first six months	EPA, Home Water Testing
Volatile organic compounds, lead, arsenic, mercury, radium, pesticides or herbicides	Ask your health or environmental department whether to test	CDC
Radon	If indoor air has radon or the region is radon rich	EPA
Nitrate, nitrite, pesticides and coliform bacteria	If there is intensive agriculture nearby	EPA

The National Ground Water Association adds any contaminants of local concern to the yearly list. Your health department can tell you what those are.

When to test sooner than once a year

The EPA says to test your well immediately if any of these apply:

There are known problems with groundwater or drinking water in your area.
Conditions near the well have changed significantly, such as flooding, land disturbance, or new construction or industrial activity.
You replace or repair any part of the well system.
You notice a change in the water's odor, color or taste.
The EPA also says you may want to test more often if small children or elderly adults live in the house, or if someone is pregnant or nursing. The National Ground Water Association adds a recently malfunctioning septic system and a history of bacterial contamination.

Where to get well water tested

The EPA says to use only laboratories that are certified to do drinking water testing. It names two routes: a state-certified laboratory, or your local health department, which may provide private well testing for free. The CDC gives the same advice and says your health department can help you understand the results.

To find a lab, the EPA's laboratory certification page links to each state's certification program.

How to collect a well water sample

Use the lab's container and follow the lab's instructions. The EPA says most laboratories supply their own sample containers, and that samples for coliform bacteria must be collected in sterile containers under sterile conditions. Extension and state guides describe the usual steps:

Pick a faucet that is not connected to a water treatment device (University of Arizona Extension).
Remove the aerator and sterilize the end of the faucet with a flame or rubbing alcohol. Penn State Extension says many labs recommend this.
Run the water before filling the bottle: 2 to 5 minutes (University of Arizona Extension), or 3 minutes at full flow (Texas Commission on Environmental Quality).
Don't set the cap down, and don't touch the inside of the cap or bottle (Penn State Extension).
Keep the sample cool and get it to the lab quickly. The published limits are 6 hours, or up to 12 at some labs (University of Arizona Extension); 24 hours (Penn State Extension); 30 hours (Texas); and 48 hours (Wisconsin DNR). Ask your lab which applies.

Can you test well water at home with a kit?

New York's health department recommends not relying on in-home tests performed by water treatment vendors or on test kits purchased at stores, because they do not meet the state's laboratory approval standards.

A University of Massachusetts Amherst study of eight home kits for iron, copper, manganese and fluoride found high variability between them: some worked well and others didn't. The EPA and CDC pages we read say to use a certified laboratory and do not discuss home kits.

How to read the results

The EPA says your results may show whether a substance exceeds a national primary or secondary drinking water standard. Those standards are written for public water systems, and private wells are not required to meet them, but they are the usual yardstick:

Total coliform: none. Penn State Extension says the drinking water standard requires that no coliform bacteria be present, and the EPA's goal for total coliforms is zero.
Nitrate: 10 milligrams per liter, measured as nitrogen (EPA).
pH: 6.5 to 8.5 (EPA secondary standard). Penn State Extension says water with a pH below 6.5 or above 8.5 can cause corrosion of lead and copper from household plumbing or bad tastes.
Total dissolved solids: 500 milligrams per liter (EPA secondary standard).

What to do if a test fails

The EPA says to contact your public health department for specific steps and to have the well re-tested to confirm the result.

For coliform bacteria, the Minnesota Department of Health says to get water from a safe alternative source such as bottled water, disinfect the well and water system with a chlorine solution, and test again. For nitrate above 10 milligrams per liter it says not to boil the water, because boiling increases the nitrate concentration, and not to give the water to infants under six months old.

Frequently Asked Questions

How often should well water be tested?

At least once a year. The EPA and CDC both say to test annually for total coliform bacteria, nitrates, total dissolved solids and pH. The EPA says to test immediately after flooding, after any repair to the well system, or if the water's odor, color or taste changes.

Can I test my well water myself?

You can collect the sample yourself, but the analysis should be done by a certified lab. The EPA says to use only laboratories certified for drinking water testing. New York's health department recommends not relying on store-bought test kits because they do not meet the state's laboratory approval standards.

Where can I get my well water tested for free?

Ask your local health department. The EPA says a local health department may provide private well testing for free. Our well water testing cost guide lists what laboratories charge when it isn't.

How long do I have to get a water sample to the lab?

It depends on the lab. For bacteria samples the published limits are 6 hours, or up to 12 at some labs (University of Arizona Extension), 24 hours (Penn State Extension), 30 hours (Texas Commission on Environmental Quality) and 48 hours (Wisconsin DNR). Keep the sample cool on the way.

Does the EPA regulate private wells?

No. The EPA says private wells are not regulated by the EPA or required to follow its standards, and that private well owners are responsible for delivering safe drinking water to their households.

Related guides and tools

General information, not a diagnosis of your system. Figures last checked against the sources below on 2026-11-13.

Sources

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